ArticlePDF AvailableLiterature Review

The Neurobiology of Psychedelic Drugs: Implications for the Treatment of Mood Disorders

Authors:

Abstract and Figures

After a pause of nearly 40 years in research into the effects of psychedelic drugs, recent advances in our understanding of the neurobiology of psychedelics, such as lysergic acid diethylamide (LSD), psilocybin and ketamine have led to renewed interest in the clinical potential of psychedelics in the treatment of various psychiatric disorders. Recent behavioural and neuroimaging data show that psychedelics modulate neural circuits that have been implicated in mood and affective disorders, and can reduce the clinical symptoms of these disorders. These findings raise the possibility that research into psychedelics might identify novel therapeutic mechanisms and approaches that are based on glutamate-driven neuroplasticity.
| Activation of the prefrontal network and glutamate release by psychedelics. a | The figure shows a model in which hallucinogens, such as psilocin, lysergic acid diethylamide (LSD) and dimethyltryptamine (DMT), increase extracellular glutamate levels in the prefrontal cortex through stimulation of postsynaptic serotonin (5-hydroxytryptamine) 2A (5-HT 2A ) receptors that are located on large glutamatergic pyramidal cells in deep cortical layers (v and vi) projecting to layer v pyramidal neurons. This glutamate release leads to an activation of AMPA (α-amino-3-hydroxy-5-methyl-4- isoxazole propionic acid) and NMDA (N-methyl-d-aspartate) receptors on cortical pyramidal neurons. in addition, hallucinogens directly activate 5-HT 2A receptors located on cortical pyramidal neurons. This activation is thought to ultimately lead to increased expression of brain-derived neurotrophic factor (BDNF). b | The figure shows a model in which dissociative NMDA antagonists, such as ketamine, block inhibitory GABA (γ-aminobutyric acid)-ergic interneurons in cortical and subcortical brain areas, leading to enhanced firing of glutamatergic projection neurons and increased extracellular glutamate levels in the prefrontal cortex. As ketamine also blocks NMDA receptors on cortical pyramidal neurons, the increased glutamate release in the cortex is thought to stimulate cortical AMPA more than NMDA receptors. The increased AMPA-receptor-mediated throughput relative to NMDA-receptor-mediated throughput is thought ultimately to lead to increased expression of BDNF.
… 
Content may be subject to copyright.
Psychedelic drugs have long held a special
fascination for mankind because they pro-
duce an altered state of consciousness that is
characterized by distortions of perception,
hallucinations or visions, ecstasy, dissolu-
tion of self boundaries and the experience
of union with the world. As plant-derived
materials, they have been used traditionally
by many indigenous cultures in medical
and religious practices for centuries, if
not millennia1.
However, research into psychedelics
did not begin until the 1950s after the
breakthrough discovery of the classical
hallucinogen lysergic acid diethylamide
(LSD) by Albert Hofmann2 (TIMELINE). The
classical hallucinogens include indoleam-
ines, such as psilocybin and LSD, and
phenethylamines, such as mescaline and
2,5-dimethoxy-4-iodo-amphetamine
(DOI). Research into psychedelics was
advanced in the mid 1960s by the finding
that dissociative anaesthetics such as keta-
mine and phencyclidine (PCP) also pro-
duce psychedelic-like effects3 (BOX 1). Given
their overlapping psychological effects,
both classes of drugs are included here
as psychedelics.
Depending on the individual taking the
drug, their expectations, the setting in which
the drug is taken and the drug dose, psych-
edelics produce a wide range of experiential
states, from feelings of boundlessness, unity
and bliss on the one hand, to the anxiety-
inducing experiences of loss of ego-control
and panic on the other hand4–7. Researchers
from different theoretical disciplines and
experimental perspectives have emphasized
different experiential states. One emphasis
has been placed on the LSD-induced percep-
tual distortions — including illusions and
hallucinations, thought disorder and
experiences of split ego7,8 — that are also
seen in naturally occurring psychoses9–11.
This perspective has prompted the use of
psychedelics as research tools for unravelling
the neuronal basis of psychotic disorders,
such as schizophrenia spectrum disorder.
The most recent work has provided com-
pelling evidence that classical hallucino-
gens primarily act as agonists of serotonin
(5-hydroxytryptamine) 2A (5-HT2A)
receptors12 and mimic mainly the so-
called positive symptoms (hallucinations
and thought disorder) of schizophrenia10.
Dissociative anaesthetics mimic the positive
and the negative symptoms (social with-
drawal and apathy) of schizophrenia
through antagonism at NMDA (N-methyl--
aspartate) glutamate receptors13,14.
Emphasis has also been placed on the
early observation that LSD can enhance
self-awareness and facilitate the recollection
of, and release from, emotionally loaded
memories15,16. This perspective appealed
to psychiatrists as a unique property that
could facilitate the psychodynamic process
during psychotherapy. In fact, by 1965 there
were more than 1,000 published clinical
studies that reported promising therapeutic
effects in over 40,000 subjects17. LSD,
psilocybin and, sporadically, ketamine have
been reported to have therapeutic effects in
patients with anxiety and obsessive–
compulsive disorders (OCD), depression,
sexual dysfunction and alcohol addiction,
and to relieve pain and anxiety in
patients with terminal cancer18–23 (BOX 2).
Unfortunately, throughout the 1960s and
1970s LSD and related drugs became
increasingly associated with cultural rebel-
lion; they were widely popularized as drugs
of abuse and were depicted in the media as
highly dangerous. Consequently, by about
1970, LSD and related drugs were placed
in Schedule I in many western countries.
Accordingly, research on the effects of
classical psychedelics in humans was
severely restricted, funding became
difficult and interests in the therapeutic
use of these drugs faded, leaving many
avenues of inquiry unexplored and
many questions unanswered.
With the development of sophisticated
neuroimaging and brain-mapping tech-
niques and with the increasing understand-
ing of the molecular mechanisms of action
of psychedelics in animals, renewed interest
in basic and clinical research with psyche-
delics in humans has steadily increased since
the 1990s. In this Perspective, we review
early and current findings of the therapeutic
effects of psychedelics and their mechanisms
of action in relation to modern concepts of
the neurobiology of psychiatric disorders.
We then evaluate the extent to which
psychedelics may be useful in therapy —
aside from their established application as
models of psychosis3,11.
OPINION
The neurobiology of psychedelic
drugs: implications for the treatment
of mood disorders
Franz X. Vollenweider and Michael Kometer
Abstract | After a pause of nearly 40 years in research into the effects of psychedelic
drugs, recent advances in our understanding of the neurobiology of psychedelics,
such as lysergic acid diethylamide (LSD), psilocybin and ketamine have led to
renewed interest in the clinical potential of psychedelics in the treatment of various
psychiatric disorders. Recent behavioural and neuroimaging data show that
psychedelics modulate neural circuits that have been implicated in mood and
affective disorders, and can reduce the clinical symptoms of these disorders. These
findings raise the possibility that research into psychedelics might identify novel
therapeutic mechanisms and approaches that are based on glutamate-driven
neuroplasticity.
PERSPECTIVES
642
|
SEPTEMBER 2010
|
VOLUME 11 www.nature.com/reviews/neuro
© 20 Macmillan Publishers Limited. All rights reserved10
Current therapeutic studies
Several preclinical studies in the 1990s
revealed an important role for the NMDA
glutamate receptor in the mechanism of
action of antidepressants. These findings
consequently gave rise to the hypothesis that
the NMDA-antagonist ketamine might have
potential as an antidepressant24. This hypoth-
esis was validated in an initial double-blind
placebo-controlled clinical study in seven
medication-free patients with major depres-
sion. Specifically, a significant reduction in
depression scores on the Hamilton depression
rating scale (HDRS) was observed 3 hours
after a single infusion of ketamine (0.5 mg
per kg), and this effect was sustained for at
least 72 hours25. Several studies have since
replicated this rapid antidepressant effect of
ketamine using larger sample sizes and treat-
ment-resistant patients with depression26–30.
Given that 71% of the patients met response
criteria (defined as a 50% reduction in HDRS
scores from baseline) within 24 hours26, this
rapid effect has a high therapeutic value. In
particular, patients with depression who are
suicidal might benefit from such a rapid and
marked effect as their acute mortality risk is
not considerably diminished with conven-
tional antidepressants owing to their long
delay in onset of action (usually 2–3 weeks).
Indeed, suicidal ideations were reduced
24 hours after a single ketamine infusion28.
However, despite these impressive and
rapid effects, all but 2 of the patients relapsed
within 2 weeks after a single dose of keta-
mine26. Previous relapse prevention strategies,
such as the administration of either five
additional ketamine infusions29 or riluzole
(Rilutek; Sanofi-aventis) on a daily basis30,
yielded success only in some patients and
other strategies should be tested in further
studies. Moreover, the use of biomarkers
that are rooted in psychopathology, neuro-
psychology and/or genetics might help to
predict whether ketamine therapy will be
appropriate for a given patient with
depression31. In line with this idea, decreased
activation of the anterior cingulate cortex
(ACC) during a working memory task32 and
increased activation of the ACC during an
emotional facial processing task33, as well
as a positive family history of alcohol
abuse27, were associated with a stronger
antidepressant response to ketamine.
Ketamine therapy could be extended to
other disorders in which NMDA receptors
are implicated in the pathophysiology — for
example, bipolar disorder34 and addic-
tion35. The use of ketamine for the treatment
of bipolar disorder is currently being tested
(Clinicaltrials.gov: NCT00947791). Its poten-
tial as a treatment for addiction is supported by
results from a double-blind, randomized clini-
cal trial in which 90 heroin addicts received
either existentially oriented psychotherapy in
combination with a high dose (2.0 mg per kg)
or a low dose of ketamine (0.2 mg per kg).
Follow-up studies in the first 2 years revealed
a higher rate of abstinence, greater and
longer-lasting reductions in craving, and a
positive change in nonverbal, unconscious
emotional attitude in subjects who had been
treated with a high dose, compared with a low
dose, of ketamine36.
In contrast to the rapidly increasing
number of clinical studies with ketamine,
studies with classic hallucinogens are
emerging slowly. This slow progress may
be due to the fact that classic hallucinogens
are placed in Schedule 1 and therefore have
higher regulatory hurdles to overcome and
may have negative connotations as a drug
of abuse.
A recent study by Moreno and
colleagues37 evaluated case reports and
findings from studies performed in the
1960s that indicated that psilocybin and LSD
are effective in the treatment of OCD22,38–40.
They subsequently carried out a study show-
ing that psilocybin given on four different
occasions at escalating doses (ranging from
sub-hallucinogenic to hallucinogenic doses)
markedly decreased OCD symptoms
(by 23–100%) on the Yale–Brown obsessive
compulsive scale in patients with OCD who
were previously treatment resistant37. The
reduction in symptoms occurred rapidly, at
about 2 h after the peak psychedelic effects,
and endured up to the 24-h post-treatment
rating37. This symptom relief was not related
to the dose of the psych edelic drug or to the
intensity of the psychedelic experience, and
extended beyond the observed acute
psychological effect of 4–6 h, raising
intriguing questions regarding the mecha-
nisms that underlie this protracted effect37.
Further research on how this initial relief of
symptoms in response to psilocybin — and
the subsequent return of symptoms — is
linked to functional changes in the brain
could contribute not only to a mechanistic
explanation of the potentially beneficial
effects of psychedelics but also to the
development of novel treatments for OCD.
The chronicity and disease burden of
OCD, the suboptimal nature of available
treatments and the observation that
psilocybin was well tolerated in OCD
patients are clear indications that further
studies into the duration, efficacy and
Timeline | A brief history of psychedelic drugs
1897 1919 1926 1938 1943 1947 1952 1953 1958 1962 1963 1965 1966 1970 1983 1988 1990 1999
Synthesis of
mescaline
by E. Späth
Isolation and
identification
of mescaline
by A. Heffter
Synthesis
of PCP
First LSD study
in people with
depression by
C. Savage
Isolation and
synthesis of
psilocin and
psilocybin by
A. Hofmann
Synthesis
of LSD by
A. Hofmann
First LSD
study in
humans by
W. Stoll
LSD appears on
the streets
Demonstration
of antagonistic
action of PCP at
NMDA receptors
by N. Anis
Sandoz recalls
samples of
LSD and
ceases
supplying it
First neuroimaging
study on psilocybin
and ketamine
Discovery of
psychoactive
effects of LSD
by A. Hofmann
First clinic using
LSD in psycholytic
therapy by
R. Sandison
Synthesis
of ketamine
Introduction
of the term
‘dissociative
anaesthetic’
by E. Domino
LSD, psilocin
and mescaline
are placed in
Schedule I in
the US
Ketamine is
placed in
schedule III
in the US
Demonstration of
agonistic action of
LSD at 5-HT2A
receptors; first
neuroimaging
study on mescaline
LSD, lysergic acid diethylamide; NMDA, N-methyl-d-aspartate; PCP, phencyclidine. Discoveries relating to classical hallucinogens and to dissociative anaesthetics are
shown by black and red boxes, respectively.
PERSPECTIVES
NATURE R EVIEWS
|
NEUROSCIENCE VOLUME 11
|
SEPTEMBER 2010
|
643
© 20 Macmillan Publishers Limited. All rights reserved10
Nature Reviews | Neuroscience
Vivid imagery
Disembodiment
Anxiety
10 20 30 40 50 60 70 20 30 40 50 60
Blissful state
Insightfulness
Psilocybin 115–125 µg per kg (n = 72)
Psilocybin 215–270 µg per kg (n = 214)
Psilocybin 315 µg per kg (n = 41)
Elementary
visual
alterations
Audio–visual
synesthaesia
Elementary
visual
alterations
Audio–visual
synesthaesia
Changed meaning
of percepts
Changed meaning
of percepts
Vivid imagery
Disembodiment
Anxiety
Blissful state
Experience
of unity
Religious
experience
Experience
of unity
Religious
experience
Insightfulness
Impaired control
and cognition
Impaired control
and cognition
Ketamine 6 µg per kg per min (n = 42)
Ketamine 12 µg per kg per min (n = 92)
mechanisms of action of psilocybin or of
related compounds in the treatment of OCD
are warranted.
Encouraged by early findings (BOX 2),
several clinical centres have begun to inves-
tigate the potential beneficial effects of psi-
locybin (ClinicalTrials.gov: NCT00302744,
NCT00957359 and NCT00465595) and LSD
(ClinicalTrials.gov: NCT00920387) in the
treatment of anxiety and depression in
patients with terminal cancer, using state
of the art, double-blind, placebo-controlled
designs. One of these studies has recently
been completed and revealed that moder-
ate doses of psilocybin improved mood and
reduced anxiety and that this relief variably
lasted between 2 weeks and 6 months in
patients with advanced cancer (C.S. Grob,
personal communication). Finally, another
recent study reported that psilocybin and LSD
aborted attacks, terminated the cluster period
or extended the remission period in people
suffering from cluster headaches41. Taken
together, these findings support early obser-
vations in the 1960s that classical hallucino-
gens have antinociceptive potential and may
not only reduce symptoms but also induce
long-lasting adaptive processes.
Neurobiology of psychedelic drugs
The enormous progress that has been made
in our understanding of the mechanisms of
action of psychedelics12,42–45 and the neurobi-
ology of affective disorders34,46,47 has enabled
us to postulate new hypotheses regarding the
therapeutic mechanisms of psychedelics and
their clinical applications. Here we focus on
the glutamatergic and serotonergic mecha-
nisms of action of psychedelics with regard
to their most promising indications — that
is, their use in the treatment of depression
and anxiety.
Classical hallucinogens. The classical hallu-
cinogens are comprised of three main chem-
ical classes: the plant-derived tryptamines
(for example, psilocybin) and phenethyl-
amines (for example, mescaline), and the
semisynthetic ergolines (for example, LSD)48.
Although all classical hallucinogens display
high affinity for 5-HT2 receptors, they also
interact to some degree with 5-HT1, 5-HT4,
5-HT5, 5-HT6 and 5-HT7 receptors12. In con-
trast to the tryptamines, the ergolines also
show high intrinsic activity at dopamine D2
receptors and at α-adrenergic receptors49.
Converging evidence from pharmaco-
logical50, electrophysiological51,52 and behav-
ioural studies in animals53,54 suggests that
classical hallucinogens produce their effects
in animals and possibly in humans primarily
through agonistic actions at cortical 5-HT2A
receptors (FIG. 1a). Consistent with this view,
selectively restoring 5-HT2A receptors in
Box 1 | Assessing altered states of consciousness
Quantifying altered states of consciousness was problematic in the early years
of hallucinogen research. Today, however, there are validated instruments
for assessing various aspects of consciousness. According to Dittrich133,
hallucinogen-induced altered states of consciousness can be reliably measured
by the five-dimensional altered states of consciousness (5DASC)
rating scale. This scale comprises five primary dimensions and their respective
subdimensions (see the figure). The primary dimensions are ‘oceanic
boundlessness’ (shown by orange boxes), referring to positively experienced
loss of ego boundaries that are associated with changes in the sense of
time and emotions — ranging from heightened mood to sublime happiness
and feelings of unity with the environment; ‘anxious ego-disintegration’
(shown by purple boxes), including thought disorder and loss of self-control;
‘visionary restructuralization’ (shown by blue boxes), referring to perceptual
alterations (such as visual illusions and hallucinations), and altered meaning of
percepts; acoustic alterations (not shown), including hypersensitivity to sound
and auditory hallucinations; and altered vigilance (not shown).
In general, the intensity of these psychedelic-induced alterations of
consciousness and perception is dose-dependent, so that hallucinations
that involve disorientation in person, place and time rarely, if ever, occur
with low to medium doses4–6. However, at larger doses — and depending
on the individual, his or her expectations and the setting — the same
hallucinogen might produce a pleasurable loss of ego boundaries combined
with feelings of oneness or might lead to a more psychotic ego dissolution
that involves fear and paranoid ideation4,132,134. Such experiential
phenomena are otherwise rarely reported except in dreams, contemplative
or religious exaltation and acute psychoses11,135. The figure shows that the
classical hallucinogen psilocybin (0.015–0.027 g per kg, by mouth) (see
the figure, left) and the dissociative s-ketamine (6–12 g per kg per min,
intravenously) (see the figure, right) produce a set of overlapping
psychological experiences, measured by the 5DASC rating scale and
respective subscales. The scales indicate the percentage scored of the
maximum score.
PERSPECTIVES
644
|
SEPTEMBER 2010
|
VOLUME 11 www.nature.com/reviews/neuro
© 20 Macmillan Publishers Limited. All rights reserved10
cortical pyramidal neurons is sufficient to
rescue hallucinogen-induced head shaking
in transgenic mice that lack 5-HT2A recep-
tors53,55. Importantly, administration of the
5-HT2A receptor antagonist ketanserin abol-
ishes virtually all of the psilocybin-induced
subjective effects in humans56. Recent stud-
ies have demonstrated that hallucinogenic
and non-hallucinogenic 5-HT2A agonists
differentially regulate intracellular signalling
pathways in cortical pyramidal neurons and
that this results in a differential expression
of downstream signalling proteins, such as
early growth response protein 1 (EGR1),
EGR2 and β-arrestin 255,57. This suggests that
further elucidation of hallucinogen-specific
signalling pathways may aid the develop-
ment of functionally selective ligands with
specific therapeutic properties — for exam-
ple, ligands that have antidepressant effects
but no hallucinogenic effects.
Several studies have demonstrated that
activation of 5-HT2A receptors by classical
hallucinogens or by serotonin leads to a
robust, glutamate-dependent increase in the
activity of pyramidal neurons, preferentially
those in layer V of the prefrontal cortex
(PFC)51,52,58,59 (FIG. 1a). This increase in
glutamatergic synaptic activity was initially
thought to result from stimulation of presy-
naptic 5-HT2A receptors located on gluta-
matergic thalamocortical afferents to the
PFC60,61. However, more recent studies sug-
gest that stimulation of postsynaptic 5-HT2A
receptors55,58,59 on a subpopulation of pyram-
idal cells in the deep layers of the PFC59 leads
to an increase in glutamatergic recurrent
network activity59,62. The increase in gluta-
matergic synaptic activity can be abolished
not only by specific 5-HT2A antagonists but
also by AMPA (α-amino-3-hydroxyl-5-
methyl-4-isoxazole-propionic acid) recep-
tor antagonists63, by agonists51 and positive
allosteric modulators of metabotropic
glutamate receptor 2 (mGluR2)64, and by
selective antagonists of the NR2B subunit
of NMDA receptors65. Taken together, these
findings indicate that classical hallucinogens
are potent modulators of prefrontal network
activity that involves a complex interaction
between the serotonin and glutamate
systems in prefrontal circuits.
Activation of 5-HT2A and 5-HT1A recep-
tors in the medial PFC (mPFC) also has
downstream effects on serotonergic and
dopaminergic activity through descend-
ing projections to the dorsal raphe and the
ventral tegmental area (VTA). For example,
activation of 5-HT2A receptors in the mPFC
increases the firing rate of 5-HT neurons in
the dorsal raphe and of dopamine neurons
in the VTA, resulting in an increased release
of 5-HT in the mPFC58,66 and of dopamine in
mesocortical areas67 in animals. In a study
in humans, the hallucinogenic 5-HT2A agon-
ist psilocybin increased striatal dopamine
concentrations, and this increase correlated
with euphoria and depersonalization
phenomena68. Blocking dopamine D2
receptors by haloperidol, however, reduced
these effects by only about 30%. This
suggests that the dopaminergic system con-
tributes only moderately to the broad spec-
trum of psilocybin-induced psychological
alterations56.
Interestingly, 5-HT2A receptor activation
not only seems to underlie the preponder-
ance of the acute psychedelic effects of hal-
lucinogens but may also lead to neuroplastic
adaptations in an extended prefrontal–limbic
network. For example, in rats a single dose
of the hallucinogen DOI transiently
increased the dendritic spine size in corti-
cal neurons69 and repeated doses of LSD
downregulated cortical 5-HT2A but not
5-HT1A receptors; effects that were the most
pronounced in the frontomedial cortex and
ACC70,71. It is possible that such adaptations —
and specifically a downregulation of prefrontal
5-HT2A receptors — might underlie some of
the therapeutic effects of hallucinogens in the
treatment of depression, anxiety and chronic
pain. In favour of this hypothesis, 5-HT2A
receptor density was found to be increased
in the PFC in post-mortem samples72 and
in vivo 73,74 in patients with major depression,
and to be reduced after chronic treatment with
various antidepressants — the reduction coin-
ciding with the onset of clinical efficacy75–77. In
addition, chronic, antisense-mediated down-
regulation of 5-HT2A receptors in rats78 and in
5-HT2A knockout mice79 reduced anxiety-like
behaviour, and selective restoration of 5-HT2A
receptors in the PFC normalized anxiety-like
behaviour in these 5-HT2A knockout mice.
These findings suggest that prefrontal 5-HT2A
receptors might modulate the activity of sub-
cortical structures, such as the amygdala79.
Anxiety and depression are interrelated with
stress80, which also affects the serotonin sys-
tem81. Stress elevates corticotropin-releasing
factor (CRF)82, and administration of CRF
into the mPFC of mice enhanced anxiety-like
Box 2 | Early therapeutic findings with psychedelics
By 1953, two forms of lysergic acid diethylamide (LSD) therapy based on different theoretical
frameworks were emerging. These have been named psychedelic (mind-manifesting)136 and
psycholytic (psyche-loosening)15 therapies. In psychedelic therapy, which was practised mostly in
North America, a large dose of LSD (200–800 g) was applied in a single session. This was thought
to induce an overwhelming and supposedly conversion-like peak experience that would bring the
subject to a new level of awareness and self-knowledge. It was thought that that this would
facilitate self-actualization and lead to permanent changes that would be beneficial to the
subject128,129. Furthermore, it was claimed that intensive psychotherapeutic preparation of the
patient before the drug session and a follow-up integration of the peak experience in further
drug-free sessions were crucial for an optimal outcome130. Promising therapeutic effects of this
therapy were found in people with terminal cancer20,137, in severe alcoholics138,139, in people who
were addicted to narcotics140 and in patients with neurosis141. For example, a series of studies
showed that LSD could reduce depression and decrease apprehension towards death and,
surprisingly, that LSD had transient analgesic effects that were superior to those of
dihydromorphinone (also known as hydromorphone and Palladone SR (Napp)) and meperidine
(also known as pethidine)20. These effects were confirmed in later studies and the clinical efficacy
was linked with the intensity of the psychedelic experience129,141,142.
Psycholytic therapy was introduced by Ronald Sandison and applied in Europe at 18 treatment
centres143. In psycholytic therapy, low to moderate doses of LSD (50–100 g), psilocybin (10–15 mg)
or, sporadically, ketamine were used repeatedly as an adjunct in psychoanalytically oriented
psychotherapy to accelerate the therapeutic process by facilitating regression and the
recollection and release of emotionally loaded repressed memories, and by increasing the
transference reaction15,22,144–147. A review of 42 studies reported impressive improvement rates in
(mostly treatment-resistant) patients with anxiety disorders (improvement in 70% of patients),
depression (in 62% of patients), personality disorders (in 53–61% of patients), sexual dysfunction
(in 50% of patients) and obsessive–compulsive disorders (in 42% of patients)148.
Unfortunately, the majority of these studies had serious methodological flaws by contemporary
standards. In particular, with the absence of adequate control groups and follow-up measurements
and with vague criteria for therapeutic outcome, the studies did not clearly establish whether it
was the drug or the therapeutic engagement that produced the reported beneficial effect. It was
also difficult to draw firm conclusions regarding potential long-term efficacy. Nevertheless, the
studies provide a conceptual framework for the application of psychedelics, with the data
suggesting that the most promising indication for psychedelic use might be found in the treatment
of depression and anxiety disorders.
PERSPECTIVES
NATURE R EVIEWS
|
NEUROSCIENCE VOLUME 11
|
SEPTEMBER 2010
|
645
© 20 Macmillan Publishers Limited. All rights reserved10
Nature Reviews | Neuroscience
Glutamate
release
Glutamate
release
NMDAR
NMDAR
AMPAR
BDNF
+
Psilocin/
LSD/DMT
5-HT2A
NMDAR
AMPAR
BDNF
+
+
+
5-HT2A
5-HT neuron
a
b
Ketamine
Ketamine
GABA
Subcortical areasCortex
Interneuron
Cortical layer V Deep cortical layers Brainstem
Psilocin/
LSD/DMT
behaviour in response to DOI through
sensitization of 5-HT2 receptor signalling in
the PFC83. In humans, fronto-limbic 5-HT2A
receptor density is correlated not only with
anxiety but also with an individual’s difficul-
ties in coping with stress84. Indeed, recent
studies showed that prefrontal 5-HT2A recep-
tors located on descending projections that
control serotonergic activity in the dorsal
raphe are involved in stress responses67,85.
Together, these findings suggest that down-
regulation of prefrontal 5-HT2A receptors by
classical hallucinogens might underlie some
of the effects of hallucinogens on depression
and anxiety.
Finally, with regard to the finding that
LSD reduces anxiety and pain in cancer
patients20, it is of note that prefrontal 5-HT2A
density correlated with responses to tonic
pain but not with responses to short pha-
sic pain stimuli. This suggests a role of the
5-HT2A receptors in the cognitive evaluation
of pain experiences86 and points to addi-
tional therapeutic potential for hallucinogens
in individuals with chronic pain.
Dissociative anaesthetics. At sub-anaesthetic
doses, dissociative anaesthetics, such as
ketamine, primarily block the NMDA recep-
tor at the PCP binding site in the receptor’s
ionotropic channel14 (FIG. 1b). The psychoac-
tive potency of the -ketamine enantiomer is
three to four times higher than that of the
-ketamine enantiomer. This is paralleled by
their relative affinities at the NMDA receptor
complex87. Systemic administration of
non-competitive NMDA antagonists, such
as ketamine, PCP and MK-801 (also
known as dizocilpine), in rats mark-
edly increases glutamate release in the
mPFC88,89 concomitant with an increase in
the firing rate of pyramidal neurons in this
area90. These effects are probably due to a
blockade of NMDA receptors on GABA
(γ-aminobutyric acid)-ergic interneurons45,91
in cortical and/or subcortical structures and
to the subsequent reduction of inhibitory
control over prefrontal glutamatergic neu-
rons92. The increased extracellular glutamate
levels in the mPFC seem to contribute to the
psychotropic effects of ketamine and PCP,
as AMPA receptor antagonists88 or agonists
of mGluR2 and mGluR3 (REF. 93) abolished
various behavioural effects of NMDA
antagonists in rats. Likewise, the behavioural
effects of selective NR2B antagonists — such
as CP-101,606 (also known as Traxoprodil),
which produces dose-dependent psycho-
tropic effects similar to those of ketamine in
humans94 — can be blocked by administra-
tion of AMPA receptor antagonists95. Finally,
lamotrigine, which reduces presynaptic
glutamate release, attenuated the subjective
effects of -ketamine in humans96.
In addition to having these glutamatergic
effects, non-competitive NMDA receptor
antagonists increase extracellular prefrontal
and mesolimbic dopamine89,93 and pre-
frontal serotonin89 levels in rats, presum-
ably by stimulating corticofugal glutamate
release in the VTA97 and the dorsal raphe89,
respectively. Studies into the contribution of
this dopaminergic and serotonergic activa-
tion to the behavioural effects of NMDA
antagonists are scant and the results are
somewhat controversial. Specifically, in
two studies in humans, ketamine-induced
striatal dopamine release correlated with
the extent of ketamine-induced psychotic
Figure 1 | Activation of the prefrontal network and glutamate release by psychedelics. a | The
figure shows a model in which hallucinogens, such as psilocin, lysergic acid diethylamide (LSD) and
dimethyltryptamine (DMT), increase extracellular glutamate levels in the prefrontal cortex through
stimulation of postsynaptic serotonin (5-hydroxytryptamine) 2A (5-HT2A) receptors that are located
on large glutamatergic pyramidal cells in deep cortical layers (V and VI) projecting to layer V pyramidal
neurons. This glutamate release leads to an activation of AMPA (α-amino-3-hydroxy-5-methyl-4-
isoxazole propionic acid) and NMDA (N-methyl-d-aspartate) receptors on cortical pyramidal neurons. In
addition, hallucinogens directly activate 5-HT2A receptors located on cortical pyramidal neurons. This
activation is thought to ultimately lead to increased expression of brain-derived neurotrophic factor
(BDNF). b | The figure shows a model in which dissociative NMDA antagonists, such as ketamine, block
inhibitory GABA (γ-aminobutyric acid)-ergic interneurons in cortical and subcortical brain areas, lead-
ing to enhanced firing of glutamatergic projection neurons and increased extracellular glutamate
levels in the prefrontal cortex. As ketamine also blocks NMDA receptors on cortical pyramidal neurons,
the increased glutamate release in the cortex is thought to stimulate cortical AMPA more than NMDA
receptors. The increased AMPA-receptor-mediated throughput relative to NMDA-receptor-mediated
throughput is thought ultimately to lead to increased expression of BDNF.
PERSPECTIVES
646
|
SEPTEMBER 2010
|
VOLUME 11 www.nature.com/reviews/neuro
© 20 Macmillan Publishers Limited. All rights reserved10
Nature Reviews | Neuroscience
ba
s-Ketamine
Psilocybin
symptoms98,99, but in another study systemic
administration of the dopamine D2 recep-
tor antagonist haloperidol did not attenuate
ketamine-induced psychotic symptoms
in healthy volunteers100. Although 5-HT2A
receptor antagonists reverse the disruptive
effects of NMDA antagonists on sensorimo-
tor gating101 and on object recognition102 in
animals, no comparable studies of the role
of serotonin in the mechanism of action of
NMDA antagonists have been conducted
in humans.
The enhanced glutamate release that
results from NMDA receptor blockade
by ketamine leads to an increased activa-
tion of AMPA receptors relative to NMDA
receptors95. The antidepressant-like effects
of ketamine and the selective NR2B antago-
nist CP-101,606 in animals can be blocked
by administration of the AMPA receptor
antagonist 2,3-dihydroxy-6-nitro-7-sul-
phamoyl-benzo[f]quinoxaline-2,3-dione
(NBQX)95, suggesting that enhanced AMPA
activation in cortical circuits is crucial for
the therapeutic effect of NMDA receptor
antagonists34,95.
A common mechanism? There is accumulat-
ing evidence that, despite their different pri-
mary modes of action, classical hallucinogens
and dissociative anaesthetics both modulate
glutamatergic neurotransmission in the pre-
frontal–limbic circuitry that is implicated in
the pathophysiology of mood disorders. This
modulation is evidenced by the observation
in rats that hallucinogens103,104 and dissocia-
tive anaesthetics88,89 have a similar effect in
enhancing extracellular glutamate release
in the PFC, leading to increased activation
of pyramidal cells63,65,105,106. Furthermore,
and congruent with these findings, human
neuroimaging studies have shown that both
psilocybin and ketamine markedly activate
prefrontal cortical areas, including the ACC
and insula and, to a lesser extent, temporal and
parieto-occipital regions107–111 (FIG. 2).
According to current models of emotion
regulation the PFC, including the ACC, exerts
cognitive’, top-down control over emotion
and stress responses through its connec-
tions to the amygdala and dorsal raphe47,85.
Reduced prefrontal glutamate levels that are
associated with attenuated PFC activation
in response to emotional stimuli34,112,113 have
been reported in patients with depression.
Further, depressed individuals46 and subjects
with high trait anxiety114 show reduced PFC
activity when executive control is engaged,
and might suffer from decreased top-
down inhibition of amygdala activity115,116.
Conversely, chronic treatment with selective
serotonin reuptake inhibitors (SSRIs) increases
the functional connectivity between the amy-
gdala and the PFC117, and attenuates the
amygdala response to the presentation of
images showing sad faces in patients with
depression118,119. This suggests that the normal-
ization of this dysregulated network might be
important in the recovery from depression46.
Given that both psilocybin and ketamine
increase extracellular glutamate levels in
the prefrontal–limbic circuitry in rats and
that the antidepressant effects of both drugs
outlast their acute psychotropic effects in
depressed patients, we propose that a
normalization of this network through
a glutamate-dependent neuroplastic adapt-
ation is the common therapeutic mechanism
of these drugs. Specifically, we posit that
psychedelics enhance neuroplasticity by
increasing AMPA-type glutamate receptor
trafficking and by raising the level of brain-
derived neurotropic factor (BDNF). Deficits
in these neuroplastic mechanisms have been
implicated in the pathophysiology of depres-
sion34,120. Normalization of these neuroplastic
deficits might contribute not only to the
relatively sustained antidepressant effects of
ketamine121,122 but also to those of psilocybin.
In line with this view, both classes of drugs
have been demonstrated to stimulate AMPA
receptors by increasing extracellular gluta-
mate levels6,95 and to increase BDNF levels in
prefrontal and limbic brain areas in rats123125.
A recent study in patients with depression,
however, failed to demonstrate an increase
in BDNF plasma levels in the first 4 h after
ketamine infusion122. Whether ketamine
treatment leads to an increase in BDNF levels
at a later time and whether such an increase
is associated with sustained antidepressant
effects warrants further investigation.
Conclusions and future directions
The clinical findings and current under-
standing of the mechanisms of action of
classical hallucinogens and dissociative
anaesthetics converge on the idea that
psychedelics might be useful in the treat-
ment of major depression, anxiety disorders
and OCD. These are serious, debilitating,
life-shortening illnesses, and as the cur-
rently available treatments have high failure
rates, psychedelics might offer alternative
Figure 2 | Brain activity patterns in psychedelic-induced states of consciousness. a | Brain
imaging studies using 18fluorodeoxyglucose [18FDG] positron emission tomography (PET) revealed that
moderate doses of s-ketamine (top) and psilocybin (bottom) in healthy volunteers increased neuronal
activity. This is shown by changes in the cerebral metabolic rate for glucose (CMRglu) in the prefrontal
cortex and associated limbic regions and in subcortical structures, including the thalamus107,109. This
similar prefrontal–limbic activation pattern supports the view that both classes of drugs have converg-
ing effects on a final pathway or neurotransmitter system. b | Recent [18FDG] PET brain imaging studies
have demonstrated that the degree to which each of the psychedelic-induced key dimensions of
altered states of consciousness (BOX 2) is manifested and correlated with functional alterations in
cortical and limbic regions and subcortical structures, including the basal ganglia and thalamus. For
example, the intensity of experience of the key dimension ‘oceanic boundlessness’ correlated with
the s-ketamine- and psilocybin-induced activation (red) of a prefrontal–parietal network and the
deactivation (blue) of a striato–limbic amygdalocentric network149.
PERSPECTIVES
NATURE R EVIEWS
|
NEUROSCIENCE VOLUME 11
|
SEPTEMBER 2010
|
647
© 20 Macmillan Publishers Limited. All rights reserved10
treatment strategies that could improve the
well-being of patients and the associated
economic burden on patients and society.
Accumulating evidence shows a crucial
role for the glutamate system in the regula-
tion of neuronal plasticity, and indicates that
abnormalities in neuroplasticity contribute
to the pathophysiology of mood disorders.
Thus, drugs that target neuronal plasticity
may offer a novel approach to their treat-
ment. This Perspective proposes that classical
psychedelics, such as psilocybin, and dis-
sociative anaesthetics, such as ketamine,
alter glutamatergic neurotransmission in
prefrontal–limbic circuitries, and that this
leads to neuroplastic adaptations, presumably
through enhancement of AMPA receptor
function. These adaptations may explain
some of the shared and relatively sustained
antidepressant effects that are observed in
clinical studies with ketamine and psilocybin.
To further validate this glutamate-induced
neuroplasticity hypothesis the relationship
between measures of glutamatergic activity
and clinical outcome needs to be established.
Moreover, the finding that classical halluci-
nogens (unlike dissociative anaesthetics) also
modulate 5-HT2A receptor signalling suggests
that they may improve subtypes of anxiety
and stress-related disorders. Studies that use
biomarkers for genotypes or that use expres-
sion levels of 5-HT2A receptors in parallel with
clinical end points would be essential not only
for clarifying the role of 5-HT2A receptors in
the therapeutic mechanism of classical hal-
lucinogens but also for the development of
personalized medicines in the treatment
of anxiety and stress-related disorders.
In addition, to optimize the clinical
benefits of psychedelics and to reduce their
unwanted side effects, a deeper understand-
ing of various factors is necessary. These
include structure–activity relationships, dose–
response relationships and the influence of
psychotherapeutic approaches on the effects
of psychedelics. In this context, it is interest-
ing to note that there was no indication of
prolonged psychosis, persisting perception
disorder or subsequent drug abuse after psi-
locybin126 or ketamine127 administration in a
large sample of psychotherapeutically well-
prepared healthy subjects in a supportive
research setting. Similar observations were
reported in small samples of patients with
depression29 and OCD37. Nonetheless, it is
often claimed that the dissociative effects of,
for example, ketamine may limit clinical use,
despite its reported efficacy24,94. In this sense,
understanding the molecular mechanism
of action could inform the development of
novel ligands for 5-HT2A or NMDA receptors
that display antidepressant properties but
have fewer dissociative effects than psilocy-
bin and ketamine. Further evaluations of the
dose–response relationship may be another
approach to minimize unwanted side effects.
For example, low to moderate oral doses of
psilocybin (<0.215 mg per kg) were found
to only rarely produce anxious dissociative
symptoms in controlled settings126 (BOX 1)
but to reduce anxiety, depression and OCD
symptoms in patients22,37. Similarly, a low
dose of the NR2B antagonist CP-101,606 (in
combination with an SSRI) had transient
antidepressant effects in a small sample of
patients with depression and only rarely
induced dissociative symptoms94.
To take the opposite perspective, it is
noteworthy that initial clinical applications of
psychedelics in psychedelic and psycholytic
therapy were based on the premise that the
drug-induced psychological experience had
an essential, facilitatory effect on the psycho-
therapeutic process — that is, it was a form
of pharmacology-assisted psychotherapy.
Indeed, it has been shown that the transcend-
ent peak (mystical-type) experience, which
has a key role in the therapeutic outcome
in psychedelic therapy128–130 and was rated
as among the most personally meaningful
experiences131,132, occurs in most cases only
in supportive settings and after high-dose
administration of psychedelics. One might
interpret this concept as an early example of
the neuroplasticity hypothesis in which the
drug-induced experience and its integration
in the psychotherapeutic process is the cru-
cial mechanism that enables neuroplasticity
and behavioural changes. By contrast, cur-
rent pharmacological strategies often assume
that medication alone produces neuroplastic
adaptations. However, drugs that increase
neuroplasticity, such as psychedelics, might
be particularly clinically efficient in com-
bination with psychotherapeutic interven-
tions121. In support of this notion, cognitive
behavioural therapy was shown to normalize
prefrontal–limbic functioning in depressed
patients46, and could therefore enhance the
proposed neuroplastic effects of psychedelics
in prefrontal–limbic structures as discussed
here. Thus, further blind, controlled studies
are obviously now needed to test these
alternative and opposing hypotheses.
The potential of drugs to target glutama-
tergic neurotransmission in prefrontal–
limbic circuitries and to facilitate neuroplas-
tic adaptations may translate into promising
new treatment approaches for affective dis-
orders. The novel hypotheses presented here
now need to be investigated using well-
controlled clinical studies, keeping in mind
the controversial history of this class of drugs.
Franz X. Vollenweider and Michael Kometer are at the
Neuropsychopharmacology and Brain Imaging
Research Unit, University Hospital of Psychiatry,
Zurich, Switzerland.
Franz X. Vollenweider is also at the School of Medicine,
University of Zurich, Switzerland.
Correspondence to F.X.V.
e‑mail: vollen@bli.uzh.ch
doi:10.1038/nrn2884
Published online 18 August 2010
Glossary
Cluster period
A period of time during which cluster headache attacks
occur regularly.
Enantiomers
Two stereoisomeric molecules that are mirror images of
each other and are not superimposable.
Existentially oriented psychotherapy
A form of therapy that emphasizes the development of a
sense of self-direction through choice and of awareness in
resolving existential conflicts (such as the inevitability of
death, isolation and meaninglessness).
Neurosis
A former term for a category of mental disorders
characterized by anxiety and a sense of distress. This
category includes disorders now classified as mood
disorders, anxiety disorders, dissociative disorders,
sexual disorders and somatoform disorders.
Psychoanalytically oriented psychotherapy
A therapy based on Freudian psychoanalysis in which
unconscious conflicts that are thought to cause the
patient’s symptoms are brought into consciousness to
create insight for the resolution of the problems.
Regression
In Freudian psychoanalytic theory this term describes a
psychological strategy to cope with reality by means of
a temporary reversion of the ego to an earlier stage of
development.
Riluzole
A drug used to treat amyotrophic lateral sclerosis and that
has NMDA (N-methyl-d-aspartate) receptor blocking
properties similar to those of ketamine.
Schedule 1
A legislative category containing controlled drugs that have
a high potential for abuse, a lack of accepted safety and no
currently accepted medical use in treatments.
Selective serotonin reuptake inhibitors
A class of compounds typically used as antidepressants.
Self-actualization
The motivation to realize all of one’s potential.
Structure–activity relationship
(Often abbreviated to SAR.) This is the relationship between
the chemical structure of a molecule and its biological activity.
Transference
A phenomenon in psychoanalysis characterized by
unconscious redirection of feelings or desires from one
person to another.
PERSPECTIVES
648
|
SEPTEMBER 2010
|
VOLUME 11 www.nature.com/reviews/neuro
© 20 Macmillan Publishers Limited. All rights reserved10
1. Hofmann, A. & Schultes, R. E. Plants of the Gods
(McGraw-Hill Book Company, Maidenhead, UK,
1979).
2. Hofmann, A. in Chemical Constitution and
Pharmacodynamic Actions (ed. Burger, A.) 169–235
(M.Dekker, New York, 1968).
3. Domino, E. F., Kamenka, J. M. & Gneste, P. The joint
French–US seminar on phencyclidine and related
arylcyclohexylamines. Trends Pharmacol. Sci. 9,
363–367 (1983).
4. Hasler, F., Grimberg, U., Benz, M. A., Huber, T. &
Vollenweider, F. X. Acute psychological and
physiological effects of psilocybin in healthy
humans: a double-blind, placebo-controlled dose-
effect study. Psychopharmacology 172, 145–156
(2004).
5. Dittrich, A. in 50 Years of LSD. Current Status and
Perspectives of Hallucinogens (eds Pletscher, A. &
Ladewig, D.) 101–118 (Parthenon, New York, 1994).
6. Fischer, R., Marks, P. A., Hill, R. M. & Rockey, M. A.
Personality structure as the main determinant of drug
induced (model) psychoses. Nature 218, 296–298
(1968).
7. Leuner, H. Die Experimentelle Psychose (Springer,
Berlin Göttingen Heidelberg, 1962).
8. Hoch, P. H., Cattell, J. P. & Pennes, H. H. Effects of
mescaline and lysergic acid (d-LSD-25). Am.
J. Psychiatry 108, 579–584 (1952).
9. Chapman, J. The early symptoms of schizophrenia.
Br. J. Psychiatry 112 , 225–251 (1966).
10. Gouzoulis-Mayfrank, E. et al. Hallucinogenic drug
induced states resemble acute endogenous psychoses:
results of an empirical study. Eur. Psychiatry 13,
399–406 (1998).
11. Geyer, M. A. & Vollenweider, F. X. Serotonin research:
contributions to understanding psychoses. Trends
Pharmacol. Sci. 29, 445–453 (2008).
12. Nichols, D. E. Hallucinogens. Pharmacol. Ther. 101,
131–181 (2004).
13. Krystal, J. H. et al. Subanesthetic effects of the
noncompetitive NMDA antagonist, ketamine, in
humans. Arch. Gen. Psychiatry 51, 199–214
(1994).
14. Anis, N. A., Berry, S. C., Burton, N. R. & Lodge, D.
The dissociative anesthetics, ketamine and
phencyclidine selective reduce excitation of central
mammalian neurons by N-methyl-D-aspartate.
Br. J. Pharmacol. 79, 565–575 (1983).
15. Sandison, R. A. Psychological aspects of the LSD
treatment of neuroses. J. Ment Sci. 100, 508–515
(1954).
16. Schmiege, G. R. Jr. LSD as a therapeutic tool. J. Med.
Soc. N.J. 60, 203–207 (1963).
17. Malleson, N. Acute adverse reactions to LSD in clinical
and experimental use in the United Kingdom.
Br. J. Psychiatry 118 , 229–230 (1971).
18. Hoffer, A. in The Uses and Implications of
Hallucinogenic Drugs (eds Aaronson, B. &
Osmond, H.) 357–366 (Hogarth Press, London,
1970).
19. Abramson, H. The use of LSD in Psychotherapy and
Alcoholism (Bobbs-Merrill, New York, 1967).
20. Kast, E. in LSD: The Consciousness Expanding Drug
(ed. Solomon, D.) 241–256 (G.P. Putman, New York,
1964).
21. Pahnke, W. N., Kurland, A. A., Goodman, L. E. &
Richards, W. A. LSD-assisted psychotherapy with
terminal cancer patients. Curr. Psychiatr. Ther. 9,
144–152 (1969).
22. Leuner, H. in 50 Years of LSD: Current Status and
Perspectives of Hallucinogen Research (eds Pletscher,
A. & Ladewig, D.) 175–189 (Parthenon, New York,
1994).
23. Kurland, A. A., Unger, S., Shaffer, J. W. & Savage, C.
Psychedelic therapy utilizing LSD in the treatment of
the alcoholic patient: a preliminary report. Am.
J. Psychiatry 123, 1202–1209 (1967).
24. Skolnick, P., Popik, P. & Trullas, R. Glutamate-based
antidepressants: 20 years on. Trends Pharmacol. Sci.
30, 563–569 (2009).
25. Berman, R. M. et al. Antidepressant effects of
ketamine in depressed patients. Biol. Psychiatry 47,
351–354 (2000).
26. Zarate, C. A. Jr et al. A randomized trial of an
N-methyl-D-aspartate antagonist in treatment-
resistant major depression. Arch. Gen. Psychiatry 63,
856–864 (2006).
27. Phelps, L. E. et al. Family history of alcohol
dependence and initial antidepressant response to an
N-methyl-D-aspartate antagonist. Biol. Psychiatry 65,
181–184 (2009).
28. Price, R. B., Nock, M. K., Charney, D. S. & Mathew, S. J.
Effects of intravenous ketamine on explicit and implicit
measures of suicidality in treatment-resistant
depression. Biol. Psychiatry 66, 522–526 (2009).
29. Aan het Rot, M. et al. Safety and efficacy of repeated-
dose intravenous ketamine for treatment-resistant
depression. Biol. Psychiatry 67, 139–145 (2010).
30. Mathew, S. J. et al. Riluzole for relapse prevention
following intravenous ketamine in treatment-resistant
depression: a pilot randomized, placebo-controlled
continuation trial. Int. J. Neuropsychopharmacol. 13,
71–82 (2010).
31. Holsboer, F. How can we realize the promise of
personalized antidepressant medicines? Nature Rev.
Neurosci. 9, 638–646 (2008).
32. Salvadore, G. et al. Anterior cingulate
desynchronization and functional connectivity with the
amygdala during a working memory task predict rapid
antidepressant response to ketamine.
Neuropsychopharmacology 35, 1415–1422
(2010).
33. Salvadore, G. et al. Increased anterior cingulate
cortical activity in response to fearful faces: a
neurophysiological biomarker that predicts rapid
antidepressant response to ketamine. Biol. Psychiatry
65, 289–295 (2009).
34. Sanacora, G., Zarate, C. A., Krystal, J. H. & Manji, H. K.
Targeting the glutamatergic system to develop novel,
improved therapeutics for mood disorders. Nature
Rev. Drug Discov. 7, 426–437 (2008).
35. Lau, C. G. & Zukin, R. S. NMDA receptor trafficking in
synaptic plasticity and neuropsychiatric disorders.
Nature Rev. Neurosci. 8, 413–426 (2007).
36. Krupitsky, E. et al. Ketamine psychotherapy for heroin
addiction: immediate effects and two-year follow-up.
J. Subst. Abuse Treatment 23, 273–283 (2002).
37. Moreno, F. A., Wiegand, C. B., Taitano, E. K. &
Delgado, P. L. Safety, tolerability, and efficacy of
psilocybin in 9 patients with obsessive-compulsive
disorder. J. Clin. Psychiatry 67, 1735–1740 (2006).
38. Brandrup, E. & Vanggaard, T. LSD treatment in a
severe case of compulsive neurosis. Acta Psychiatr.
Scand. 55, 127–141 (1977).
39. Leonard, H. L. & Rapoport, J. L. Relief of obsessive–
compulsive symptoms by LSD and psilocin. Am.
J. Psychiatry 144, 1239–1240 (1987).
40. Moreno, F. A. & Delgado, P. L. Hallucinogen-induced
relief of obsessions and compulsions. Am.
J. Psychiatry 154, 1037–1038 (1997).
41. Sewell, R. A., Halpern, J. H. & Pope, H. G. Jr.
Response of cluster headache to psilocybin and LSD.
Neurology 66, 1920–1922 (2006).
42. Gonzalez-Maeso, J. & Sealfon, S. C. Agonist-trafficking
and hallucinogens. Curr. Med. Chem. 16, 1017–1027
(2009).
43. Winter, J. C. Hallucinogens as discriminative stimuli
in animals: LSD, phenethylamines, and tryptamines.
Psychopharmacology (Berlin) 203, 251–263 (2009).
44. Large, C. H. Do NMDA receptor antagonist models of
schizophrenia predict the clinical efficacy of antipsychotic
drugs? J. Psychopharmacol. 21, 283–301 (2007).
45. Quirk, M. C., Sosulski, D. L., Feierstein, C. E.,
Uchida, N. & Mainen, Z. F. A defined network of fast-
spiking interneurons in orbitofrontal cortex: responses
to behavioral contingencies and ketamine
administration. Front. Syst. Neurosci. 3, 13 (2009).
46. DeRubeis, R. J., Siegle, G. J. & Hollon, S. D. Cognitive
therapy versus medication for depression: treatment
outcomes and neural mechanisms. Nature Rev.
Neurosci. 9, 788–796 (2008).
47. Clark, L., Chamberlain, S. R. & Sahakian, B. J.
Neurocognitive mechanisms in depression:
implications for treatment. Annu. Rev. Neurosci. 32,
57–74 (2009).
48. Geyer, M. A., Nichols, D. E. & Vollenweider, F. X.
in Encyclopedia of Neuroscience (ed. Squire, L. R.)
741–748 (Academic Press, Oxford, 2009).
49. Marona-Lewicka, D., Thisted, R. A. & Nichols, D. E.
Distinct temporal phases in the behavioral
pharmacology of LSD: dopamine D2 receptor-
mediated effects in the rat and implications for
psychosis. Psychopharmacologia (Berlin) 180,
427–435 (2005).
50. Glennon, R. A., Titeler, M. & McKenney, J. D. Evidence
for 5-HT2 involvement in the mechanism of action of
hallucinogenic agents. Life Sci. 35, 2505–2511
(1984).
51. Aghajanian, G. K. & Marek, G. J. Serotonin induces
excitatory postsynaptic potentials in apical dendrites
of neocortical pyramidal cells.
Neuropsychopharmacology 36, 589–599 (1997).
52. Aghajanian, G. K. & Marek, G. J. Serotonin, via
5-HT2A receptors, increases EPSCs in layer V
pyramidal cells of prefrontal cortex by an
asynchronous mode of glutamate release. Brain Res.
825, 161–171 (1999).
53. Wing, L. L., Tapson, G. S. & Geyer, M. A. 5HT-2
mediation of acute behavioral effects of hallucinogens
in rats. Psychopharmacology 100, 417–425 (1990).
54. Sipes, T. E. & Geyer, M. A. DOI disruption of prepulse
inhibition of startle in the rat is mediated by 5-HT2A
and not by 5-HT2C receptors. Behav. Pharmacol. 6,
839–842 (1995).
55. Gonzalez-Maeso, J. et al. Hallucinogens recruit specific
cortical 5-HT(2A) receptor-mediated signaling
pathways to affect behavior. Neuron 53, 439–452
(2007).
56. Vollenweider, F. X., Vollenweider-Scherpenhuyzen,
M. F. I., Bäbler, A., Vogel, H. & Hell, D. Psilocybin
induces schizophrenia-like psychosis in humans via
a serotonin-2 agonist action. Neuroreport 9,
3897–3902 (1998).
57. Schmid, C. L., Raehal, K. M. & Bohn, L. M.
Agonist-directed signaling of the serotonin 2A
receptor depends on b-arrestin-2 interactions in vivo.
Proc. Natl Acad. Sci. USA 105, 1079–1084 (2008).
58. Puig, M. V., Celada, P., az-Mataix, L. & Artigas, F.
In vivo modulation of the activity of pyramidal neurons
in the rat medial prefrontal cortex by 5-HT2A
receptors: relationship to thalamocortical afferents.
Cereb. Cortex 13, 870–882 (2003).
59. Beique, J. C., Imad, M., Mladenovic, L., Gingrich, J. A.
& Andrade, R. Mechanism of the 5-hydroxytryptamine
2A receptor-mediated facilitation of synaptic activity in
prefrontal cortex. Proc. Natl Acad. Sci. USA 104,
9870–9875 (2007).
60. Aghajanian, G. K. & Marek, G. J. Serotonin and
hallucinogens. Neuropsychopharmacology 21,
16S–23S (1999).
61. Marek, G. J., Wright, R. A., Gewirtz, J. C. &
Schoepp, D. D. A major role for thalamocortical
afferents in serotonergic hallucinogen receptor
function in the rat neocortex. Neuroscience 105,
379–392 (2001).
62. Aghajanian, G. K. Modeling ‘psychosis’ in vitro by
inducing disordered neuronal network activity in
cortical brain slices. Psychopharmacology (Berlin)
206, 575–585 (2009).
63. Zhang, C. & Marek, G. J. AMPA receptor involvement
in 5-hydroxytryptamine2A receptor-mediated pre-
frontal cortical excitatory synaptic currents and DOI-
induced head shakes. Prog. Neuropsychopharmacol.
Biol. Psychiatry 32, 62–71 (2008).
64. Benneyworth, M. A. et al. A selective positive
allosteric modulator of metabotropic glutamate
receptor subtype 2 blocks a hallucinogenic drug model
of psychosis. Mol. Pharmacol. 72, 477–484 (2007).
65. Lambe, E. K. & Aghajanian, G. K. Hallucinogen-
induced UP states in the brain slice of rat prefrontal
cortex: role of glutamate spillover and NR2B-NMDA
receptors. Neuropsychopharmacology 31, 1682–
1689 (2006).
66. Celada, P., Puig, M. V., Casanovas, J. M., Guillazo, G.
& Artigas, F. Control of dorsal raphe serotonergic
neurons by the medial prefrontal cortex: Involvement
of serotonin-1A, GABA(A), and glutamate receptors.
J. Neurosci. 21, 9917–9929 (2001).
67. Vazquez-Borsetti, P., Cortes, R. & Artigas, F. Pyramidal
neurons in rat prefrontal cortex projecting to ventral
tegmental area and dorsal raphe nucleus express
5-HT2A receptors. Cereb. Cortex 19, 1678–1686
(2009).
68. Vollenweider, F. X., Vontobel, P., Hell, D. & Leenders,
K. L. 5-HT modulation of dopamine release in basal
ganglia in psilocybin-induced psychosis in man: A PET
study with [11C]raclopride.
Neuropsychopharmacology 20, 424–433 (1999).
69. Jones, K. A. et al. Rapid modulation of spine
morphology by the 5-HT2A serotonin receptor
through kalirin-7 signaling. Proc. Natl Acad. Sci. USA
106, 19575–19580 (2009).
70. Buckholtz, N. S., Zhou, D. F., Freedman, D. X. &
Potter, W. Z. Lysergic acid diethylamide (LSD)
administration selectively downregulates serotonin2
receptors in rat brain. Neuropsychopharmacology 3,
137–148 (1990).
71. Gresch, P. J., Smith, R. L., Barrett, R. J. &
Sanders-Bush, E. Behavioral tolerance to lysergic acid
diethylamide is associated with reduced serotonin-2A
receptor signaling in rat cortex.
Neuropsychopharmacology 30, 1693–1702
(2005).
PERSPECTIVES
NATURE R EVIEWS
|
NEUROSCIENCE VOLUME 11
|
SEPTEMBER 2010
|
649
© 20 Macmillan Publishers Limited. All rights reserved10
72. Shelton, R. C., Sanders-Bush, E., Manier, D. H. &
Lewis, D. A. Elevated 5-HT 2A receptors in
postmortem prefrontal cortex in major depression is
associated with reduced activity of protein kinase, A.
Neuroscience 158, 1406–1415 (2008).
73. Bhagwagar, Z. et al. Increased 5-HT2A receptor binding
in euthymic, medication-free patients recovered from
depression: a positron emission study with [11C]MDL
100,907. Am. J. Psychiatry 163, 1580–1587
(2006).
74. Meyer, J. H. et al. Dysfunctional attitudes and 5-HT2
receptors during depression and self-harm. Am.
J. Psychiatry 160, 90–99 (2003).
75. Sibille, E. et al. Antisense inhibition of
5-hydroxytryptamine2a receptor induces an
antidepressant-like effect in mice. Mol. Pharmacol.
52, 1056–1063 (1997).
76. Yamauchi, M., Miyara, T., Matsushima, T. &
Imanishi, T. Desensitization of 5-HT2A receptor
function by chronic administration of selective
serotonin reuptake inhibitors. Brain Res. 1067,
164–169 (2006).
77. Gomez-Gil, E. et al. Decrease of the platelet 5-HT2A
receptor function by long-term imipramine treatment
in endogenous depression. Hum. Psychopharmacol.
19, 251–258 (2004).
78. Cohen, H. Anxiolytic effect and memory improvement
in rats by antisense oligodeoxynucleotide to
5-hydroxytryptamine-2A precursor protein. Depress.
Anxiety. 22, 84–93 (2005).
79. Weisstaub, N. V. et al. Cortical 5-HT2A receptor
signaling modulates anxiety-like behaviors in mice.
Science 313, 536–540 (2006).
80. Anisman, H., Merali, Z. & Stead, J. D. Experiential and
genetic contributions to depressive- and anxiety-like
disorders: clinical and experimental studies. Neurosci.
Biobehav. Rev. 32, 1185–1206 (2008).
81. Lukkes, J., Vuong, S., Scholl, J., Oliver, H. & Forster, G.
Corticotropin-releasing factor receptor antagonism
within the dorsal raphe nucleus reduces social anxiety-
like behavior after early-life social isolation.
J. Neurosci. 29, 9955–9960 (2009).
82. Reul, J. M. & Holsboer, F. Corticotropin-releasing
factor receptors 1 and 2 in anxiety and depression.
Curr. Opin. Pharmacol. 2, 23–33 (2002).
83. Magalhaes, A. C. et al. CRF receptor 1 regulates
anxiety behavior via sensitization of 5-HT2 receptor
signaling. Nature Neurosci. 13, 622–629 (2010).
84. Frokjaer, V. G. et al. Frontolimbic serotonin 2A
receptor binding in healthy subjects is associated with
personality risk factors for affective disorder. Biol.
Psychiatry 63, 569–576 (2008).
85. Amat, J. et al. Medial prefrontal cortex determines
how stressor controllability affects behavior and
dorsal raphe nucleus. Nature Neurosci. 8, 365–371
(2005).
86. Kupers, R. et al. A PET [18F]altanserin study of
5-HT12A receptor binding in the human brain and
responses to painful heat stimulation. Neuroimage
44, 1001–1007 (2009).
87. Oye, I., Paulsen, O. & Maurset, A. Effects of ketamine
on sensory perception: Evidence for a role of
N-methyl-d-aspartate receptors. J. Pharmac. Exp.
Ther. 260, 1209–1213 (1992).
88. Moghaddam, B., Adams, B., Verma, A. & Daly, D.
Activation of glutamatergic neurotransmission by
ketamine: a novel step in the pathway from NMDA
receptor blockade to dopaminergic and cognitive
disruptions associated with the prefrontal cortex.
J. Neurosci. 17, 2921–2927 (1997).
89. Lopez-Gil, X. et al. Clozapine and haloperidol
differently suppress the MK-801-increased
glutamatergic and serotonergic transmission in the
medial prefrontal cortex of the rat.
Neuropsychopharmacology 32, 2087–2097 (2007).
90. Jackson, M. E., Homayoun, H. & Moghaddam, B.
NMDA receptor hypofunction produces concomitant
firing rate potentiation and burst activity reduction in
the prefrontal cortex. Proc. Natl Acad. Sci. USA 101,
8467–8472 (2004).
91. Homayoun, H. & Moghaddam, B. NMDA receptor
hypofunction produces opposite effects on prefrontal
cortex interneurons and pyramidal neurons.
J. Neurosci. 27, 11496–11500 (2007).
92. Jodo, E. et al. Activation of medial prefrontal cortex by
phencyclidine is mediated via a hippocampo-prefrontal
pathway. Cereb. Cortex 15, 663–669 (2005).
93. Moghaddam, B. & Adams, B. W. Reversal of
phencyclidine effects by a group II metabotropic
glutamate receptor agonist in rats. Science 281,
1349–1352 (1998).
94. Preskorn, S. H. et al. An innovative design to establish
proof of concept of the antidepressant effects of the
NR2B subunit selective N-methyl-D-aspartate
antagonist, CP-101,606, in patients with treatment-
refractory major depressive disorder. J. Clin.
Psychopharmacol. 28, 631–637 (2008).
95. Maeng, S. et al. Cellular mechanisms underlying the
antidepressant effects of ketamine: role of α-amino-
3-hydroxy-5-methylisoxazole-4-propionic acid
receptors. Biol. Psychiatry 63, 349–352 (2008).
96. Anand, A. et al. Attenuation of the neuropsychiatric
effects of ketamine with lamotrigine: support for
hyperglutamatergic effects of N-methyl-D-aspartate
receptor antagonists. Arch. Gen. Psychiatry 57,
270–276 (2000).
97. Jentsch, J. D., Tran, A., Taylor, J. R. & Roth, R. H.
Prefrontal cortical involvement in phencyclidine-
induced activation of the mesolimbic dopamine
system: behavioral and neurochemical evidence.
Psychopharmacology (Berlin) 138, 89–95 (1998).
98. Breier, A. et al. Effects of NMDA antagonism on
striatal dopamine release in healthy subjects —
application of a novel PET approach. Synapse 29,
142–147 (1998).
99. Vollenweider, F. X., Vontobel, P., Leenders, K. L. &
Hell, D. Effects of S-ketamine on striatal dopamine
release: a [11C] raclopride PET study of a model
psychosis in humans. J. Psych. Res. 34, 35–43 (2000).
100. Krystal, J. H. et al. Interactive effects of subanesthetic
ketamine and haloperidol in healthy humans.
Psychopharmacology 145, 193–204 (1999).
101. Varty, G. B., Bakshi, V. P. & Geyer, M. A. M100907, a
serotonin 5-HT2A
receptor antagonist and putative
antipsychotic, blocks dizocilpine-induced prepulse
inhibition deficits in sprague-dawley and wistar rats.
Neuropsychopharmacology 20, 311–321 (1999).
102. Snigdha, S. et al. Attenuation of phencyclidine-induced
object recognition deficits by the combination of
atypical antipsychotic drugs and pimavanserin (ACP
103), a 5-hydroxytryptamine(2A) receptor inverse
agonist. J. Pharmacol. Exp. Ther. 332, 622–631 (2010).
103. Scruggs, J. L., Schmidt, D. & Deutch, A. Y. The
hallucinogen 1-[2,5-dimethoxy-4-iodophenyl]-
2-aminopropane (DOI) increases cortical extracellular
glutamate levels in rats. Neurosci. Lett. 346,
137–140 (2003).
104. Muschamp, J. W., Regina, M. J., Hull, E. M.,
Winter, J. C. & Rabin, R. A. Lysergic acid diethylamide
and [-]-2,5-dimethoxy-4-methylamphetamine increase
extracellular glutamate in rat prefrontal cortex. Brain
Res. 1023, 134–140 (2004).
105. Kargieman, L., Santana, N., Mengod, G., Celada, P. &
Artigas, F. Antipsychotic drugs reverse the disruption
in prefrontal cortex function produced by NMDA
receptor blockade with phencyclidine. Proc. Natl Acad.
Sci. USA 104, 14843–14848 (2007).
106. Shi, W. X. & Zhang, X. X. Dendritic glutamate-induced
bursting in the prefrontal cortex: further
characterization and effects of phencyclidine.
J. Pharmacol. Exp. Ther. 305, 680–687 (2003).
107. Vollenweider, F. X. et al. Metabolic hyperfrontality and
psychopathology in the ketamine model of psychosis
using positron emission tomography (PET) and [F-18]-
fluorodeoxyglocose (FDG). Eur.
Neuropsychopharmacol. 7, 9–24 (1997).
108. Vollenweider, F. X. et al. Positron emission tomography
and fluorodeoxyglucose studies of metabolic
hyperfrontality and psychopathology in the psilocybin
model of psychosis. Neuropsychopharmacology 16,
357–372 (1997).
109. Vollenweider, F. X., Leenders, K. L., Oye, I., Hell, D. &
Angst, J. Differential psychopathology and patterns of
cerebral glucose utilisation produced by (S)- and
(R)-ketamine in healthy volunteers measured by
FDG-PET. Eur. Neuropsychopharmacol. 7, 25–38
(1997).
110. Schreckenberger, M. et al. The psilocybin psychosis as
a model psychosis paradigma for acute schizophrenia:
a PET study with 18-FDG. Eur. J. Nucl. Med. 25, 877
(1998).
111. Gouzoulis-Mayfrank, E. et al. Neurometabolic effects
of psilocybin, 3,4-methylenedioxyethylamphetamine
(MDE) and d-methamphetamine in healthy volunteers.
A double-blind, placebo-controlled PET study with
[18F]FDG. Neuropsychopharmacology 20, 565–581
(1999).
112. Walter, M. et al. The relationship between aberrant
neuronal activation in the pregenual anterior
cingulate, altered glutamatergic metabolism, and
anhedonia in major depression. Arch. Gen. Psychiatry
66, 478–486 (2009).
113. Hasler, G. et al. Reduced prefrontal glutamate/
glutamine and gamma-aminobutyric acid levels in
major depression determined using proton magnetic
resonance spectroscopy. Arch. Gen. Psychiatry 64,
193–200 (2007).
114. Bishop, S. J. Trait anxiety and impoverished prefrontal
control of attention. Nature Neurosci. 12, 92–98
(2009).
115. Bishop, S. J. Neural mechanisms underlying selective
attention to threat. Ann. NY Acad. Sci. 1129,
141–152 (2008).
116. Johnstone, T., van Reekum, C. M., Urry, H. L.,
Kalin, N. H. & Davidson, R. J. Failure to regulate:
counterproductive recruitment of top-down prefrontal-
subcortical circuitry in major depression. J. Neurosci.
27, 8877–8884 (2007).
117. Chen, C. H. et al. Functional coupling of the amygdala
in depressed patients treated with antidepressant
medication. Neuropsychopharmacology 33,
1909–1918 (2008).
118. Fu, C. H. et al. Attenuation of the neural response to
sad faces in major depression by antidepressant
treatment: a prospective, event-related functional
magnetic resonance imaging study. Arch. Gen.
Psychiatry 61, 877–889 (2004).
119. Sheline, Y. I. et al. Increased amygdala response
to masked emotional faces in depressed
subjects resolves with antidepressant treatment:
an fMRI study. Biol. Psychiatry 50, 651–658 (2001).
120. Martinowich, K., Manji, H. & Lu, B. New insights into
BDNF function in depression and anxiety. Nature
Neurosci. 10, 1089–1093 (2007).
121. Krystal, J. H. et al. Neuroplasticity as a target for the
pharmacotherapy of anxiety disorders, mood
disorders, and schizophrenia. Drug Discov. Today 14,
690–697 (2009).
122. Machado-Vieira, R., Salvadore, G., DiazGranados, N.
& Zarate, C. A. Jr. Ketamine and the next
generation of antidepressants with a rapid onset
of action. Pharmacol. Ther. 123, 143–150 (2009).
123. Vaidya, V. A., Marek, G. J., Aghajanian, G. K. &
Duman, R. S. 5-HT2A receptor-mediated regulation
of brain-derived neurotrophic factor mRNA in the
hippocampus and the neocortex. J. Neurosci. 17,
2785–2795 (1997).
124. Cavus, I. & Duman, R. S. Influence of estradiol, stress,
and 5-HT2A agonist treatment on brain-derived
neurotrophic factor expression in female rats. Biol.
Psychiatry 54, 59–69 (2003).
125. Garcia, L. S. et al. Ketamine treatment reverses
behavioral and physiological alterations induced by
chronic mild stress in rats. Prog.
Neuropsychopharmacol. Biol. Psychiatry 33,
450–455 (2009).
126. Studerus, E., Kometer, M., Hasler, F. &
Vollenweider, F. X. Acute, subacute and long-term
subjective effects of psilocybin in healthy humans: a
pooled analysis of experimental studies.
J. Psychopharmacology (in the press).
127. Perry, E. B. Jr et al. Psychiatric safety of ketamine in
psychopharmacology research. Psychopharmacology
(Berlin) 192, 253–260 (2007).
128. Savage, C., Savage, E., Fadiman, J. & Harman, W. W.
LSD: Therapeutic effects of the psychedelic experience.
Psychol. Rep. 14, 111–120 (1964).
129. Pahnke, W. N., Kurland, A. A., Unger, S., Savage, C. &
Grof, S. The experimental use of psychedelic (LSD)
psychotherapy. JAMA 212 , 1856–1863 (1970).
130. Kurland, A. A., Grof, S. & Panke, W. N. G. L. E. LSD in
the treatment of alcoholics. Pharmakopsychiatr.
Neuropsychopharmakol. 4, 83–94 (1971).
131. Griffiths, R. R., Richards, W., Johnson, M., McCann, U.
& Jesse, R. Mystical-type experiences occasioned by
psilocybin mediate the attribution of personal
meaning and spiritual significance 14 months later.
J. Psychopharmacol. 22, 621–632 (2008).
132. Griffiths, R. R., Richards, W. A., McCann, U. & Jesse, R.
Psilocybin can occasion mystical-type experiences
having substantial and sustained personal meaning
and spiritual significance. Psychopharmacology
(Berlin) 187, 268–283 (2006).
133. Dittrich, A. The standardized psychometric
assessment of altered states of consciousness
(ASCs) in humans. Pharmacopsychiatry 31, 80–84
(1998).
134. Vollenweider, F. X. Advances and pathophysiological
models of hallucinogen drug actions in humans: a
preamble to schizophrenia research.
Pharmacopsychiatry 31, 92–103 (1998).
135. Fischer, R. A cartography of the ecstatic and
meditative states. Science 174, 897–904 (1971).
PERSPECTIVES
650
|
SEPTEMBER 2010
|
VOLUME 11 www.nature.com/reviews/neuro
© 20 Macmillan Publishers Limited. All rights reserved10
136. Osmond, H. A review of the clinical effects of
psychotomimetic agents. Ann. NY Acad. Sci. 66,
418–434 (1957).
137. Kurland, A. A. LSD in the supportive care of the
terminally ill cancer patient. J. Psychoactive Drugs
17, 279–290 (1985).
138. Abramson, H. A. The Use of LSD in Psychotherapy
and Alcoholism (Bobbs-Merrill, Indianapolis, 1967).
139. Hollister, L. E., Shelton, J. & Krieger, G. A controlled
comparison of lysergic acid diethylamide (LSD) and
dextroamphetmine in alcoholics. Am. J. Psychiatry
125, 1352–1357 (1969).
140. Savage, C. & McCabe, O. L. Residential psychedelic
(LSD) therapy for the narcotic addict. A controlled
study. Arch. Gen. Psychiatry 28, 808–814 (1973).
141. Grof, S., Goodman, L. E., Richards, W. A. & Kurland,
A. A. LSD-assisted psychotherapy in patients with
terminal cancer. Int. Pharmacopsychiatry 8,
129–144 (1973).
142. Pahnke, W. N. Psychedelic drugs and mystical
experience. Int. Psychiatry Clin. 5, 149–162
(1969).
143. Grinspoon, L. & Bakalar, J. B. Psychedelic Drugs
Reconsidered (Basic Books., New York, 1979).
144. Crocket, R., Sandison, R. A. & Walk, A. in Proc.
R. Med–Psychol. Assoc. (Lewis & Co., London,
1963).
145. Leuner H. in Ethnopsychotherapie (eds Dittrich, A. &
Scharfetter, C.) 151–161 (Enke, Stuttgard, 1987)
146. Geert-Jorgensen, E. Further observations regarding
hallucinogenic treatment. Acta Psychiatr. Scand. 203
(Suppl.), 195–200 (1968).
147. Khorramzadeh, E. & Lotfy, A. O. The use of ketamine
in psychiatry. Psychosomatics 14, 344–346 (1973).
148. Mascher, E. in Neuro‑Psychopharmacology (eds Brill, H.,
Cole, J. O., Denker, P., Hippins, H. & Bradley, P. B.)
441–444 (Excerpta-Medica, Amsterdam, 2010).
149. Vollenweider, F. X. Brain mechanisms of hallucinogens
and entactogens. Dialogues Clin. Neurosci. 3,
265–279 (2001).
Acknowledgements
The authors would like to acknowledge the financial support
of the Swiss Neuromatrix Foundation (to F.X.V. and M.K.),
and of the Heffter Research Institute (to F.X.V.). The authors
thank D. Nichols for critical comments on the manuscript.
Competing interests statement
The authors declare no competing financial interests.
DATABASES
ClinicalTrials.gov: http://clinicaltrials.gov
NCT00302744 | NCT00465595 | NCT00920387 |
NCT00947791 | NCT00957359
UniProtKB: http://www.uniprot.org
b-arrestin 2 | EGR1 | EGR2 | mGluR2 | mGluR3
FURTHER INFORMATION
University of Zurich Neuropsychopharmacology and Brain
Imaging Group’s homepage: http://www.dcp.uzh.ch/
research/groups/neuropsychopharmacology.html
ALL LINKS ARE ACTIVE IN THE ONLINE PDF
SCIENCE AND SOCIETY
Socioeconomic status and the brain:
mechanistic insights from human
and animal research
Daniel A. Hackman, Martha J. Farah and Michael J. Meaney
Abstract | Human brain development occurs within a socioeconomic context and
childhood socioeconomic status (SES) influences neural development
particularly of the systems that subserve language and executive function.
Research in humans and in animal models has implicated prenatal factors,
parent–child interactions and cognitive stimulation in the home environment in
the effects of SES on neural development. These findings provide a unique
opportunity for understanding how environmental factors can lead to individual
differences in brain development, and for improving the programmes and policies
that are designed to alleviate SES-related disparities in mental health and
academic achievement.
As the field of human neuroscience has
matured, it has progressed from describing
the ‘typical’ or ‘average’ human brain to
characterizing individual differences in
brain structure and function, and identify-
ing their determinants. Socioeconomic sta-
tus (SES), a measure of ones overall status
and position in society, strongly influences
an individual’s experiences from child-
hood and through adult life. Research is
beginning to shed light on the mechanisms
through which experiences in the social
world during early childhood affect the
structure and function of the brain.
Growing up in a family with low SES is
associated with substantially worse health
and impaired psychological well-being, and
impaired cognitive and emotional develop-
ment throughout the lifespan1–6. In con-
trast to sociological and epidemiological
approaches, neuroscience can identify the
underlying cognitive and affective systems
that are influenced by SES (BOX 1). In addi-
tion, neuroscience research — in animals
and in humans — has provided candidate
mechanisms for the cause–effect relation-
ships between SES and neural development.
This research has also demonstrated that at
least some of these effects are reversible. Such
a mechanistic understanding will enable the
design of more specific and powerful inter-
ventions to prevent and remediate the effects
of low childhood SES7–9.
Other recent reviews have discussed
research on SES-related differences in
neurocognitive development7–9. In this
Perspective, we focus on the candidate
mechanisms by which SES influences brain
development, drawing from research in
humans and in animal models. We first
describe studies in humans that show that
SES influences cognitive and affective func-
tion in children, adolescents and young
adults. We then discuss studies in human
populations that have identified possible
mediators of the effects of SES, and review
research in animals in which these factors
were directly manipulated to assess their
effect on offspring outcomes.
SES effects on mental health and cognition
SES is a complex construct that is based
on household income, material resources,
education and occupation, as well as related
neighbourhood and family characteristics,
such as exposure to violence and toxins,
parental care and provision of a cognitively
stimulating environment2,5,10,11 (for con-
troversies regarding the measurement and
defining levels of SES see REFS 1,10,11). Not
only the lowest stratum but all levels of SES
affect emotional and cognitive development
to varying degrees1,12–14. This implies that the
effects of SES that are reviewed here are
relevant to the entire population, although
it should be noted that the strongest effects
are often seen in people with the lowest
levels of SES.
Compared with children and adolescents
from higher-SES backgrounds, children
and adolescents from low-SES backgrounds
show higher rates of depression, anxiety,
attention problems and conduct disor-
ders12,15–18, and a higher prevalence of inter-
nalizing (that is, depression- or anxiety-like)
and externalizing (that is, aggressive and
impulsive) behaviours6,19–21, all of which
increase with the duration of impoverish-
ment12,21. In addition, childhood SES influ-
ences cognitive development; it is positively
correlated with intelligence and academic
achievement from early childhood and
through adolescence2,3,6,14,19,22,23.
PERSPECTIVES
NATURE R EVIEWS
|
NEUROSCIENCE VOLUME 11
|
SEPTEMBER 2010
|
651
© 20 Macmillan Publishers Limited. All rights reserved10
... For this reason, the 5-HT2AR might be critically involved in the relationship between stress and alcohol drinking. However, the neural mechanisms linking 5-HT2AR activation to positive therapeutic outcomes remains unclear (Vollenweider & Kometer, 2010). Promotion of neuronal Clhomeostasis, dictated by KCC2 in VTA GABA neurons, may underlie the therapeutic success of 5-HT2AR agonists. ...
Article
Alcohol use is a prominent contributor to global disease burden and a leading cause of preventable mortality. Long-term severe problem drinking is clinically diagnosed as alcohol use disorder (AUD), one of the most prevalent neuropsychiatric diseases worldwide. Despite the persistent public health concern posed by alcohol abuse, treatments targeting specific brain mechanisms impacted by and driving pathological alcohol use are lacking. Behavioral animal models have revealed that the mesolimbic dopamine reward pathway is a critical mediator of alcohol’s reinforcing effects. The ventral tegmental area (VTA) is a central hub of this reward circuitry and subversion of alcohol-induced neuronal activity in the VTA has been linked to increased alcohol consumption. Among its many effects in the brain, alcohol enhances release of the inhibitory neurotransmitter GABA in the VTA. This acute effect of alcohol is exacerbated by prior alcohol, drug, or stress exposure, which are all risk factors for subsequent alcohol abuse. For these reasons, the central hypothesis of this dissertation was that disruptions in alcohol-induced inhibitory GABA signaling in the VTA contribute to escalated alcohol consumption. To delineate the mechanisms of disturbed VTA inhibitory transmission that may lead to increased alcohol consumption, electrophysiological recordings, in vivo pharmacological manipulations, and alcohol self-administration paradigms were performed in rodents. The second and third chapters provide evidence that an acute stressor in adulthood or chronic nicotine exposure in adolescence promote subsequent alcohol self-administration behavior via chloride ion (Cl-) dysregulation in VTA GABA neurons. Normalizing Cl- homeostasis by intra-VTA pharmacological upregulation of the potassium-Cl- cotransporter KCC2 prevented the increased alcohol drinking phenotype observed after stress or nicotine. In the fourth and fifth chapters, rescue of disrupted Cl- homeostasis via serotonin 2A receptor (5-HT2AR) activation is demonstrated ex vivo and correlated with 5-HT2AR agonist-mediated reduction in heavy alcohol consumption. Collectively, this body of work suggests that dysregulation of VTA Cl- transport, dictated largely by KCC2 function, increases risk for alcohol abuse. Targeting this form of inhibitory plasticity represents a novel interventional approach for AUD. Therefore, future work is needed to identify clinically safe and efficacious pharmacotherapies to reverse disturbances in midbrain Cl- homeostasis in alcohol-dependent individuals.
... The rapid-acting dissociative agent ketamine, which has shown its efficacy in treating depression, is known to increase BDNF levels (37,38). It has been suggested that the persisting therapeutic effects of psychedelics are attributable to a similar biological mechanism (39,40). ...
Article
Full-text available
Clinical studies suggest the therapeutic potential of psychedelics, including ayahuasca, DMT, psilocybin, and LSD, in stress-related disorders. These substances induce cognitive, antidepressant, anxiolytic, and antiaddictive effects suggested to arise from biological changes similar to conventional antidepressants or the rapid-acting substance ketamine. The proposed route is by inducing brain neuroplasticity. This review attempts to summarize the evidence that psychedelics induce neuroplasticity by focusing on psychedelics' cellular and molecular neuroplasticity effects after single and repeated administration. When behavioral parameters are encountered in the selected studies, the biological pathways will be linked to the behavioral effects. Additionally, knowledge gaps in the underlying biology of clinical outcomes of psychedelics are highlighted. The literature searched yielded 344 results. Title and abstract screening reduced the sample to 35; eight were included from other sources, and full-text screening resulted in the final selection of 16 preclinical and four clinical studies. Studies ( n = 20) show that a single administration of a psychedelic produces rapid changes in plasticity mechanisms on a molecular, neuronal, synaptic, and dendritic level. The expression of plasticity-related genes and proteins, including Brain-Derived Neurotrophic Factor (BDNF), is changed after a single administration of psychedelics, resulting in changed neuroplasticity. The latter included more dendritic complexity, which outlasted the acute effects of the psychedelic. Repeated administration of a psychedelic directly stimulated neurogenesis and increased BDNF mRNA levels up to a month after treatment. Findings from the current review demonstrate that psychedelics induce molecular and cellular adaptations related to neuroplasticity and suggest those run parallel to the clinical effects of psychedelics, potentially underlying them. Future (pre)clinical research might focus on deciphering the specific cellular mechanism activated by different psychedelics and related to long-term clinical and biological effects to increase our understanding of the therapeutic potential of these compounds.
... The term "psychedelics" refers to wide class of psychoactive compounds, most of them naturally-occurring, capable of producing alterations in consciousness via their pharmacological effects on diverse neurotransmitter systems. "Classical" serotonergic psychedelics, including psilocybin and LSD, act as agonists on the serotonin system, with relative selectivity for the 5HT 2A receptor (24), whilst dissociative psychedelics, such as ketamine, hijack the glutamatergic system, acting as NMDAR antagonists (25). Consumption of such compounds leads to altered states of consciousness, characterised by sensory perturbations, including pseudo-hallucinations, as well as the reemergence of emotional content, which can lead to long-lasting insights after the experience has ended (26)(27)(28). ...
Article
Full-text available
Mindfulness-based interventions and psychedelic-assisted therapy have been experimentally utilised in recent years as alternative treatments for various psychopathologies with moderate to great success. Both have also demonstrated significant post-acute and long-term decreases in clinical symptoms and enhancements in well-being in healthy participants. These two therapeutic interventions share various postulated salutogenic mechanisms, such as the ability to alter present-moment awareness and anti-depressive action, via corresponding neuromodulatory effects. Recent preliminary evidence has also demonstrated that psychedelic administration can enhance mindfulness capacities which has already been demonstrated robustly as a result of mindfulness-based interventions. These shared mechanisms between mindfulness-based interventions and psychedelic therapy have led to scientists theorising, and recently demonstrating, synergistic effects when both are used in combination, in the form of potentiated therapeutic benefit. These synergistic results hold great promise but require replication in bigger sample groups and better controlled methodologies, to fully delineate the effect of set and setting, before they can be extended onto clinical populations.
... Though not yet as intensively investigated, ayahuasca, ibogaine, and lysergic acid diethylamide (LSD), have also shown treatment potential for substance use and psychiatric disorders (Begola and Schillerstrom 2019;Vollenweider and Kometer 2010). ...
Article
Despite resurgent interest in psychedelic-assisted therapy, our insights into psychiatrists’ knowledge and opinions about medicinal psychedelic applications are surprisingly narrow. Therefore, we anonymously surveyed psychiatrists attending psychedelic didactic presentations at two national meetings about these issues using a 26-item questionnaire. Response rate was 40.20% (106/264). Respondents were 41.73 ± 13.31 years old (range: 24–80) and 64.42% were male. They largely believed psychedelics show treatment promise and strongly supported federal funding for medicinal psychedelic research. The most common concerns were the lack of trained psychedelic-assisted therapy providers, the logistics of psychedelic-assisted therapy delivery, the administration of psychedelics for patients with contraindications, and diversion. The most desired psychedelic-related educational topics were potential benefits of psychedelic-assisted therapy, how to conduct psychedelic-assisted therapy, psychedelic pharmacology, and psychedelic side effects. Factors associated with increased belief in psychedelics’ treatment potential included working primarily in research, scoring higher on a psychedelic knowledge test, and reporting less concern about psychedelics’ addictive potential. Working primarily in research and consult-liaison psychiatry fellowship training were positively associated with support for medicinal psychedelic legalization, while increased concerns about addictive potential and attending psychiatrist status were negatively associated. Support for legalization of non-medicinal psychedelic use was negatively associated with age and positively associated with support for legalization of medicinal psychedelic use.
... The term "psychedelics" refers to wide class of psychoactive compounds, most of them naturally-occurring, capable of producing alterations in consciousness via their pharmacological effects on diverse neurotransmitter systems. "Classical" serotonergic psychedelics, including psilocybin and LSD, act as agonists on the serotonin system, with relative selectivity for the 5HT 2A receptor (24), whilst dissociative psychedelics, such as ketamine, hijack the glutamatergic system, acting as NMDAR antagonists (25). Consumption of such compounds leads to altered states of consciousness, characterised by sensory perturbations, including pseudo-hallucinations, as well as the reemergence of emotional content, which can lead to long-lasting insights after the experience has ended (26)(27)(28). ...
Article
Full-text available
Mindfulness-based interventions and psychedelic-assisted therapy have been experimentally utilised in recent years as alternative treatments for various psychopathologies with moderate to great success. Both have also demonstrated significant post-acute and long-term decreases in clinical symptoms and enhancements in well-being in healthy participants. These two therapeutic interventions share various postulated salutogenic mechanisms, such as the ability to alter present-moment awareness and anti-depressive action, via corresponding neuromodulatory effects. Recent preliminary evidence has also demonstrated that psychedelic administration can enhance mindfulness capacities which has already been demonstrated robustly as a result of mindfulness-based interventions. These shared mechanisms between mindfulness-based interventions and psychedelic therapy have led to scientists theorising, and recently demonstrating, synergistic effects when both are used in combination, in the form of potentiated therapeutic benefit. These synergistic results hold great promise but require replication in bigger sample groups and better controlled methodologies, to fully delineate the effect of set and setting, before they can be extended onto clinical populations.
... Furthermore, recent results indicate the therapeutic potential of psychedelic-assisted therapy as effective treatment option for various psychiatric disorders (Grob et al. 2011;Bogenschutz et al. 2015;Rucker et al. 2016;Bogenschutz and Ross 2018;Carhart-Harris et al. 2018). Psi produces a dosedependent altered state of consciousness and induces transient and reversible alterations in body and self-perception which are closely linked to each other (Vollenweider and Kometer 2010;Studerus et al. 2011;Preller and Vollenweider 2018). ...
Article
As source of sensory information, the body provides a sense of agency and self/non-self-discrimination. The integration of bodily states and sensory inputs with prior beliefs has been linked to the generation of bodily self-consciousness. The ability to detect surprising tactile stimuli is essential for the survival of an organism and for the formation of mental body representations. Despite the relevance for a variety of psychiatric disorders characterized by altered body and self-perception, the neurobiology of these processes is poorly understood. We therefore investigated the effect of psilocybin (Psi), known to induce alterations in self-experience, on tactile mismatch responses by combining pharmacological manipulations with simultaneous electroencephalography–functional magnetic resonance imaging (EEG–fMRI) recording. Psi reduced activity in response to tactile surprising stimuli in frontal regions, the visual cortex, and the cerebellum. Furthermore, Psi reduced tactile mismatch negativity EEG responses at frontal electrodes, associated with alterations of body- and self-experience. This study provides first evidence that Psi alters the integration of tactile sensory inputs through aberrant prediction error processing and highlights the importance of the 5-HT2A system in tactile deviancy processing as well as in the integration of bodily and self-related stimuli. These findings may have important implications for the treatment of psychiatric disorders characterized by aberrant bodily self-awareness.
... Recent years have experienced a resurgence of clinical interest in the use of psychedelics as therapeutics for the treatment of mood disorders, alcohol and substance abuse, and end-of-life distress in terminally-ill patients (Carhart-Harris and Goodwin, 2017;Nichols et al., 2017;Vollenweider and Preller, 2020). The common therapeutic mechanism of serotonergic psychedelic drugs remains unclear, although multiple lines of evidence now point to 5-HT 2A receptor-mediated glutamate release (Vollenweider and Kometer, 2010;Mason et al., 2020;Vollenweider and Preller, 2020). Spatial gradients in drug targets, such as serotonergic receptor subtypes, can be approximated using the topography of gene transcripts -particularly in the case of receptors for which the field lacks suitable PET radioligands. ...
Article
Full-text available
Psychoactive drugs can transiently perturb brain physiology while preserving brain structure. The role of physiological state in shaping neural function can therefore be investigated through neuroimaging of pharmacologically induced effects. Previously, using pharmacological neuroimaging, we found that neural and experiential effects of lysergic acid diethylamide (LSD) are attributable to agonism of the serotonin-2A receptor (Preller et al., 2018). Here, we integrate brain-wide transcriptomics with biophysically based circuit modeling to simulate acute neuromodulatory effects of LSD on human cortical large-scale spatiotemporal dynamics. Our model captures the inter-areal topography of LSD-induced changes in cortical blood oxygen level-dependent (BOLD) functional connectivity. These findings suggest that serotonin-2A-mediated modulation of pyramidal-neuronal gain is a circuit mechanism through which LSD alters cortical functional topography. Individual-subject model fitting captures patterns of individual neural differences in pharmacological response related to altered states of consciousness. This work establishes a framework for linking molecular-level manipulations to systems-level functional alterations, with implications for precision medicine.
Article
After decades of stagnation, research on psychedelic substances (such as lysergic acid diethylamide [LSD], psilocybin, or N,N-dimethyltryptamine [DMT]) has experienced a renaissance over the last 10 years, with various major research programs being conducted across Europe and the United States. This research primarily investigates the potential of psychedelics in the treatment of mental health disorders, their short- and long-term effects on recreational users, and the neurological and cognitive processes responsible for their effects. The present review provides a concise summary of the most recent insights gained from this research. We briefly outline the history of psychedelic research, the objective and subjective effects caused by these substances, the prevalence and socio-psychological correlates of their use, as well as their potential for harm. Subsequently, we review empirical research on the beneficial effects of psychedelics in clinical samples, focusing on their efficacy in the treatment of major depression, anxiety, and substance use disorders, and discuss research on the proposed neural and cognitive mechanisms behind these effects. We then review research on their effects on healthy subjects, focusing on psychological well-being as well as changes in personality, nature-relatedness, and creativity. Finally, we review empirical evidence regarding the long-term effects of single experiences with psychedelics and conclude with a summary and outlook.
Article
Full-text available
Many people who have had a near-death experience (NDE) describe, as part of it, a disturbed sense of having a “distinct self”. However, no empirical studies have been conducted to explore the frequency or intensity of these effects. We surveyed 100 NDE experiencers (Near-Death-Experience Content [NDE-C] scale total score ≥27/80). Eighty participants had their NDEs in life-threatening situations and 20 had theirs not related to life-threatening situations. Participants completed the Ego-Dissolution Inventory (EDI) and the Ego-Inflation Inventory (EII) to assess the experience of ego dissolution and inflation potentially experienced during their NDE, respectively. They also completed the Nature-Relatedness Scale (NR-6) which measures the trait-like construct of one’s self-identification with nature. Based on prior hypotheses, ratings of specific NDE-C items pertaining to out-of-body experiences and a sense of unity were used for correlational analyses. We found higher EDI total scores compared with EII total scores in our sample. Total scores of the NDE-C scale were positively correlated with EDI total scores and, although less strongly, the EII and NR-6 scores. EDI total scores were also positively correlated with the intensity of OBE and a sense of unity. This study suggests that the experience of dissolved ego-boundaries is a common feature of NDEs.
Article
Prepulse inhibition (PPI) of the startle response is used as a measure of sensorimotor inhibitory processes. Deficits in PPI have been found in patients with schizophrenia, obsessive compulsive disorder (OCD) and Huntington's disease. PPI can also be disrupted in animals through manipulations that augment serotonergic activity, such as administration of the serotonin (5-HT) agonists 8-OH-DPAT, RU 24969 and DOI. In the present experiment the identity of the 5-HT receptor subtype that mediates the DOI-induced disruption of PPI was examined. Dose-response studies revealed that the novel 5-HT(2A) antagonist, MDL 100,907 (0.01, 0.1 and 1.0 mg/kg, s.c.), but not the new 5-HT(2C) antagonist SDZ SER 082 (0.125, 0.25 and 0.5 mg/kg, s.c.), prevented the loss of PPI induced by DOI (0.25 or 0.5 mg/kg, s.c.). The results support the hypothesis that the 5-HT(2A) receptor is involved in the modulation of sensorimotor gating. Because deficits in PPI are used as a model of sensorimotor gating abnormalities found in schizophrenia, the present study supports the view that MDL 100,907 may be a novel atypical antipsychotic. Studies of the serotonergic substrates of PPI may provide a model of the possible serotonergic role in the sensorimotor gating abnormalities in schizophrenia and OCD patients.
Article
The history of research with psychedelic drugs has produced a variety of methods for their use and conflicting claims about results. First came the wave of excitement among experimentalists in the 1950s when it was claimed that lysergic acid diethylamide (LSD) could produce a model psychosis which might be useful in understanding schizophrenia. While this promise was fading, enthusiastic reports about the possibility of LSD as an aid to psychotherapy in the treatment of alcoholism and other psychiatric disorders appeared. All these approaches were represented in 1959 at the first international conference devoted entirely to LSD.1 Since then, there have been at least five more published proceedings of such conferences on various aspects of psychedelic drugs.2-6 The most recent conference on various means of producing states of consciousness was sponsored by the Menninger Foundation and the American Association of Humanistic Psychology on April 7 to 11, 1969, in
Article
Background: To characterize further behavioral, cognitive, neuroendocrine, and physiological effects of subanesthetic doses of ketamine hydrochloride in healthy human subjects. Ketamine, a phencyclidine hydrochloride derivative, is a dissociative anesthetic and a noncompetitive antagonist of the N-methyl-D-aspartate subtype of excitatory amino acid receptor.Methods: Nineteen healthy subjects recruited by advertisements from the community participated in this randomized, double-blind, placebo-controlled study. Subjects completed three test days involving the 40-minute intravenous administration of placebo, ketamine hydrochloride (0.1 mg/kg), or ketamine hydrochloride (0.5 mg/kg). Behaviors associated with the positive and negative symptoms of schizophrenia were assessed by using the Brief Psychiatric Rating Scale. Changes in perception and behaviors associated with dissociative states were assessed by the Perceptual Aberration Subscale of the Wisconsin Psychosis Proneness Scale and the Clinician-Administered Dissociative States Scale. Cognitive function was assessed by using the (1) Mini-Mental State Examination; (2) tests sensitive to frontal cortical dysfunction, including a continuous performance vigilance task, a verbal fluency task, and the Wisconsin Card Sorting Test; and (3) tests of immediate and delayed recall. Plasma levels of cortisol, prolactin, homovanillic acid, and 3-methoxy-4-hydroxyphenethyleneglycol were measured.Results: Ketamine (1) produced behaviors similar to the positive and negative symptoms of schizophrenia; (2) elicited alterations in perception; (3) impaired performance on tests of vigilance, verbal fluency, and the Wisconsin Card Sorting Test; (4) evoked symptoms similar to dissociative states; and (5) preferentially disrupted delayed word recall, sparing immediate recall and postdistraction recall. Ketamine had no significant effect on the Mini-Mental State Examination at the doses studied. Ketamine also had no effect on plasma 3-methoxy-4hydroxyphenethyleneglycol levels, although it blunted a test day decline in plasma homovanillic acid levels at the higher dose. It also dose dependently increased plasma cortisol and prolactin levels. Ketamine produced small dose-dependent increases in blood pressure.Conclusions: These data indicate that N-methyl-Daspartate antagonists produce a broad range of symptoms, behaviors, and cognitive deficits that resemble aspects of endogenous psychoses, particularly schizophrenia and dissociative states.