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Upregulation of CB1 receptors and agonist-stimulated [35S]GTPS binding in the prefrontal cortex of depressed suicide victims


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Endogenous and exogenous cannabinoids (CBs) acting through the CB(1) receptors have been implicated in the regulation of several behavioral and neuroendocrine functions. Modulation of endocannabinoidergic system by ethanol in mouse brain, and the association of suicide and mood disorders with alcoholism suggest possible involvement of the cannabinoidergic system in the pathophysiology of depression and suicide. Therefore, the present study was undertaken to examine the levels of CB(1) receptors and mediated signaling in the dorsolateral prefrontal cortex (DLPFC) of subjects with major depression who had died by suicides (depressed suicides, DS). [(3)H]CP-55,940 and CB(1) receptor-stimulated [(35)S]GTPgammaS binding sites were analyzed in membranes obtained from DLPFC of DS (10) and matched normal controls (10). Upregulation (24%, P<0.0001) of CB(1) receptor density (B(max)) was observed in DS (644.6+/-48.8 fmol/mg protein) compared with matched controls (493.3+/-52.7 fmol/mg protein). However, there was no significant alteration in the affinity of receptor (DS; 1.14+/-0.08 vs control; 1.12+/-0.10 nM). Higher density of CB(1) receptors in DS (38%, P<0.001) was also demonstrated by Western blot analysis. The CB(1) receptor-stimulated [(35)S]GTPgammaS binding was significantly greater (45%, P<0.001) in the DLPFC of DS compared with matched controls. The observed upregulation of CB(1) receptors with concomitant increase in the CB(1) receptor-mediated [(35)S]GTPgammaS binding suggests a role for enhanced cannabinoidergic signaling in the prefrontal cortex of DS. The cannabinoidergic system may be a novel therapeutic target in the treatment of depression and/or suicidal behavior.
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Upregulation of CB
receptors and agonist-stimulated
S]GTPcS binding in the prefrontal cortex of depressed
suicide victims
BL Hungund
, KY Vinod
, SA Kassir
, BS Basavarajappa
, R Yalamanchili
, TB Cooper
JJ Mann
and V Arango
New York State Psychiatric Institute, New York, NY, USA;
Nathan Kline Institute for Psychiatric Research, Orangeburg, NY,
Department of Psychiatry, College of Physicians and Surgeons, Columbia University, New York, NY, USA;
of Anatomy and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY, USA
Endogenous and exogenous cannabinoids (CBs) acting through the CB
receptors have been
implicated in the regulation of several behavioral and neuroendocrine functions. Modulation of
endocannabinoidergic system by ethanol in mouse brain, and the association of suicide and
mood disorders with alcoholism suggest possible involvement of the cannabinoidergic
system in the pathophysiology of depression and suicide. Therefore, the present study was
undertaken to examine the levels of CB
receptors and mediated signaling in the dorsolateral
prefrontal cortex (DLPFC) of subjects with major depression who had died by suicides
(depressed suicides, DS). [
H]CP-55,940 and CB
receptor-stimulated [
S]GTPcS binding sites
were analyzed in membranes obtained from DLPFC of DS (10) and matched normal controls
(10). Upregulation (24%, Po0.0001) of CB
receptor density (B
) was observed in DS
(644.6748.8 fmol/mg protein) compared with matched controls (493.3752.7 fmol/mg protein).
However, there was no significant alteration in the affinity of receptor (DS; 1.1470.08 vs
control; 1.1270.10 nM). Higher density of CB
receptors in DS (38%, Po0.001) was also
demonstrated by Western blot analysis. The CB
receptor-stimulated [
S]GTPcS binding was
significantly greater (45%, Po0.001) in the DLPFC of DS compared with matched controls. The
observed upregulation of CB
receptors with concomitant increase in the CB
mediated [
S]GTPcS binding suggests a role for enhanced cannabinoidergic signaling in the
prefrontal cortex of DS. The cannabinoidergic system may be a novel therapeutic target in the
treatment of depression and/or suicidal behavior.
Molecular Psychiatry (2004) 9, 184–190. doi:10.1038/
Keywords: CB
receptor; [
S]GTPgS binding; depression; suicide; prefrontal cortex
Cannabinoid (CB) receptors received their name
as those receptors that bind cannabinoidergic
drugs, such as 9-tetrahydrocannabinol (D
derived from Cannabis sativa and its biologically
active synthetic analogs. D
-THC is the major
psychoactive component in marijuana extracts
and can produce a multiplicity of effects in
humans, including alterations in mood, percep-
tion, cognition and memory.
is currently the most widely abused drug second
to alcohol. However, the functional significance
of the cannabinoidergic system in health and
disease is just beginning to emerge.
Significant progress has been made in characteriz-
ing CB receptors both centrally and peripherally, and
in studying the role of second messenger systems at
the cellular level. To date, two types of CB receptors,
and CB
, have been identified
and have been
shown to belong to G-protein coupled receptor
(GPCR) family. Two endogenous cannabimimetic
substances, characterized to be N-arachidonyl etha-
nolamide (AEA/anandamide) and 2-arachidonylgly-
cerol (2-AG), were discovered and shown to act as
agonists for CB receptors.
The CB
receptor is
distributed primarily in neural tissue, whereas CB
receptor is expressed mainly in the peripheral
immune system.
These receptors exhibit seven
transmembrane domains, linked to G
protein to
inhibit adenylyl cyclase.
Interestingly, the CB
receptor is one of the most abundant neuromodula-
tory receptors in the brain and is expressed predomi-
nantly in the cerebral cortex, hippocampus,
cerebellum and basal ganglia.
Received 20 January 2003; revised 7 March 2003; accepted 10
March 2003
Correspondence: Dr BL Hungund, Nathan Kline Institute for
Psychiatric Research, Bldg 39, 140 Old Orangeburg Road,
Orangeburg, NY 10962, USA;
BLH and KYV contributed equally to this work.
Molecular Psychiatry (2004) 9, 184 190
2004 Nature Publishing Group All rights reserved 1359-4184/04
Numerous studies have implicated alterations in
several receptors and G-protein function in the
pathophysiology of various neurological and psychia-
tric disorders. Decreased CB
receptor binding in
neurodegenerative diseases related to extrapyramidal
function has been reported.
Alterations in the
serotonergic (for a review see, Arango et al
) and
receptors in the pathophysiology of
depression and suicidal behavior are well documen-
ted. Recently, Dean et al,
reported increased CB
receptor density in dorsolateral prefrontal cortex
(DLPFC) in schizophrenia.
The increased levels of endocannabinoids and
downregulation of CB
receptor in response to
chronic ethanol intake in mouse brain suggest
modulation of the endocannabinoidergic system by
(for a review, see Hungund et al
). The
mood and cognition altering ability of exogenous
cannabinoids and alcohol, and the association be-
tween depression, suicide and alcohol abuse raise the
question whether endogenous cannabinoidergic sys-
tem plays any role in the etiology of depression and
suicidal behavior. Therefore, to address this question,
we studied the density of CB
receptors and CB
receptor-mediated [
S]GTPgS binding in prefrontal
cortex of subjects with major depression who had
died by suicides. Further studies of the role of the
cannabinoidergic system in various neuropsychiatric
disorders would be of great interest.
Materials and methods
Human brain tissue
Brain samples of prefrontal cortex were obtained from
autopsy material derived from the brain tissue
collection of the Department of Neuroscience at the
New York State Psychiatric Institute (NYSPI) and
Columbia University, NY, USA. All tissue used in this
study was provided by the Allegheny County Coroner
in accordance with protocols approved by the
Institutional Review Board of the University of
Pittsburgh. Brains were collected and bisected at
autopsy. The right hemispheres were cut coronally
into 1.5-cm thick sections. Blocks were placed on a
glass slide, immersed in freon (201C) and stored at
801C in tightly sealed, thick plastic bags until
sectioning. After a control and suicide were matched,
coronal sections (20 mm) from the hemicerebrum were
taken from a level just anterior to the genu of the
corpus callosum with a large format Leica Cryopoly-
cut cryostat. Interleaved sections every 200 mm were
sectioned at 50 mm and stained with cresylecht violet
for cytoarchitectonics. Once the sectioning was
completed, Brodmann area 9 was identified using
gyral and sulcal landmarks, cytoarchitecture and a
standardized coronal atlas (Robert Perry and Edward
Bird, personal communication), as previously de-
Tissue from Brodmann area 9 (B1.5 g) was
dissected frozen, the white matter was removed as
much as possible, and tissue returned immediately to
–801C until membrane preparation.
The study was conducted with approval from the
NYSPI Institutional Review Board. Dorsolateral pre-
frontal cortex postmortem samples (Brodmann area 9)
from 10 normal controls (age range: 15–79 years) were
studied with a matched group of 10 subjects who had
a lifetime diagnosis of major depression and died by
suicide (age range: 13–77 years). The groups com-
prised pairs of depressed suicides (DS) and control
cases matched for age, sex, postmortem interval (PMI)
and ethnic group. There were nine pairs of caucasians
and one pair of African-Americans (2nd pair in Table
1). This distribution reflects the ethnic make-up of
Allegheny County, where the samples were collected.
There were no significant differences in age, sex and
PMI distribution between DS and control subjects.
The demographic variables, such as sex, age, PMI and
cause of death, as well as toxicology results, are
summarized in Table 1. The Coroner determined the
cause of death and reached the verdict of suicide.
Toxicological analyses were performed on all the
cases, ruling out recent consumption of substance of
abuse or psychoactive medication except in three
samples where an anxiolytic drug (n ¼ 1) and ethanol
(n ¼ 3) were detected. Two individuals received
lidocaine as part of resuscitation efforts at the
emergency room. All cases were free of neuropathol-
ogy. Both suicides and controls were examined
psychiatrically by structured interviews with family
members and/or close friends. The psychiatric diag-
noses were made according to DSM-III-R criteria.
The psychological autopsies revealed that all suicide
victims had a lifetime diagnosis of major depression
and all controls were free of psychopathology. The
samples were coded to mask investigators to the
diagnostic group of all subjects. All the assays were
carried out in a paired design under the same
experimental conditions.
Membrane preparation
Brain tissue (B1 g) was homogenized in 20 volumes
of ice-cold TME buffer (50 mM Tris-HCl, 3 mM MgCl
and 1 mM of EDTA, pH 7.4) containing 0.32 M sucrose
and freshly added protease inhibitor cocktail. The
homogenate was centrifuged at 1000 g for 10 min at
41C. The resulting supernatant was then centrifuged
at 22 000 g for 20 min. The pellet was dissolved in
TME buffer and recentrifuged at 22 000 g for 20 min.
The final pellet, dissolved in TME buffer, was made
aliquots and stored at –801C until the assay.
Determination of protein content
The protein content of the membrane fraction was
determined by Lowry’s method
using bovine serum
albumin (BSA) as the standard. Protein content of the
membrane, also normalized by silver staining, was
used for Western blot analysis.
H]CP-55,940 binding assay
An aliquot of membrane (100 mg protein) was incu-
bated with TME buffer, [
H]CP-55,940 (0.05–5.0 nM)
and 0.1% fatty acid-free BSA in silicone-treated test
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
tubes for 1 h at 371C. The nonspecific binding of
radioligand was defined by CP-55,940 (10 mM). The
reaction was terminated by the addition of 2 ml ice-
cold termination buffer (0.1% BSA in 50 mM Tris-
HCl, pH 7.4). The reaction mixture was rapidly
filtered through polyethyleneimine (0.1%) pretreated
glass fiber filters using a Brandel 24-position cell
harvester (Brandel, Gaithersburg, MD, USA). Filters,
washed three times with the termination buffer, were
transferred to scintillation vials containing 5 ml of
scintillation cocktail (ICN biochemicals, USA), and
were incubated overnight at room temperature. The
radioactivity was measured by liquid scintillation
spectroscopy (Beckman) at an efficiency of 47% for
receptor-stimulated [
S]GTPgS binding assay
The functional coupling between CB
receptor and
G-protein was assessed by [
S]GTPgS binding assay
as described previously
with minor modification.
Briefly, an aliquot of membrane (50 mg protein) was
incubated in assay buffer (TME buffer and 0.1% fatty
acid-free BSA and 100 mM NaCl) containing GDP
(40 mM), and [
S]GTPgS (0.05 nM) in silicone-treated
test tubes for 1 h at 371C. The CB
receptor agonist,
CP-55,940 (1 mM), was used to study CB
stimulated [
S]GTPgS binding. The nonspecific bind-
ing of radioligand was determined in the presence of
10 mM GTPgS. The termination and filtration (without
presoaking the filters in polyethyleneimine) of
reaction mixture was performed as described for
H]CP-55,940 binding assay. The radioactivity was
measured by liquid scintillation spectroscopy at an
efficiency of 95% for
Western blot analysis
Briefly, aliquots of membrane protein (30 mg), sepa-
rated by 10% polyacrylamide gel, were electrophor-
etically transferred to nitrocellulose membrane. The
membrane was treated with blocking buffer (TTBS
(10 mM Tris, 0.9% NaCl; 1% Tween 20 containing 3%
milk powder) of pH 7.4) for 1 h at room temperature.
The membrane was incubated with human anti-CB
receptor antibody (1 : 500) overnight at 41C. The blot
was washed three times with TTBS and then
incubated with alkaline phosphatase-conjugated
anti-IgG for 1 h at room temperature. After washing
the blot for 3–4 times with TTBS, the immunoreactive
band was visualized by CDP-star reagent. The blot
was reprobed with a-tubulin antibody to ensure equal
protein loading.
Data and statistical analysis
The B
(maximal binding sites) and K
dissociation constant) values were determined from
saturation isotherms using nonlinear regression ana-
lysis to fit the data to the single-site binding equation
(Prism; GraphPad software). The density and affinity
of CB
receptor was expressed as fmol/mg protein and
nM, respectively. The CB
Table 1 Demographic characteristics of DS and their matched control subjects
Diagnosis Sex (M/F) Age at death (years) PMI (h) Cause of death Toxicology
1. MDD M 13 18 Suicide, NaOH poisoning None
Control M 15 16 Homicide, GSW None
2. MDD M 14 16 Suicide, hanging None
Control M 17 14 Homicide, GSW Alcohol
3. MDD M 17 17 Suicide, GSW None
Control M 16 18 Accident, asphyxia None
4. MDD M 25 18 Suicide, GSW Alcohol
Control M 25 18 Accident, explosion Alcohol
5. MDD F 28 19 Suicide, fall from height None
Control F 27 15 MVA, pedestrian None
6. MDD F 34 04 Suicide, hanging None
Control F 38 07 Homocide, GSW None
7. MDD F 43 12 Suicide, poisoning ANX, OPIA, ACE
Control F 42 16 Homicide, GSW None
8. MDD F 61 11 Suicide, hanging None
Control F 56 18 MVA, passenger None
9. MDD M 64 19 Suicide, GSW LIDO
Control M 66 19 Natural, cardiovascular None
10. MDD M 77 18 Suicide, hanging None
Control M 79 10 Natural, cardiovascular LIDO
MDD (10) 6M/4F 37.677.2 15.971.4
Control (10) 6M/4F 38.17 7.1 15.071.2
The data are presented as mean7SEM. MDD, major depressive disorder; GSW, gun shot wound; MVA, motor vehicle
accident; PMI, postmortem interval (rounded to near hours); ANX, anxiolytic; LIDO, lidocaine; OPIA, opiates; ACE,
acetaminophen; Low level of alcohol was detected in three cases (0.02–0.03%).
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
S]GTPgS binding expressed as fmol/mg protein’ is
a percentage of stimulation over the basal activity.
Statistical analysis performed using nonparametric
analysis of variance (Mann–Whitney U) and para-
metric (paired Student t’-test). Differences were
considered to be significant at Po0.05. Immunoblots
were analyzed using the NIH image software program.
Data are expressed as mean7SEM from two to three
experiments, each run in at least duplicate unless
otherwise indicated.
S]GTPgS and [
H]CP-55,940 were purchased from
DuPont NEN (Boston, MA, USA). Fatty acid-free BSA,
protease inhibitor cocktail, GDP and GTPgS were
procured from Sigma Co (St Louis, MO, USA). Glass
fiber filters (GF/B) were purchased from Brandel Inc.
(Gaithersburg, MD, USA). CP-55,940 was a gift from
Pfizer Pharmaceutical (Groton, CT, USA). Human
receptor was obtained from Biosource Inter-
nationals (California, CA, USA). Anti-a-tubulin
monoclonal antibody was from Amersham Bioscience
(Piscataway, NJ, USA). Alkaline phosphatase-conju-
gated anti-IgG was obtained from Promega (Madison,
WI, USA). CDP-star chemiluminescence kit was
purchased from Tropix (Bedford, MA, USA). Other
chemicals, of analytical grade, were purchased from
standard commercial sources.
The density of CB
A saturation analysis suggests that [
binding is saturable below 5.0 nM concentration.
The nonspecific binding was about 15% of total
H]CP-55,940 binding. A Scatchard analysis of the
binding data indicates a monophasic binding of
radioligand, and Hill’s coefficient of near unity
suggests the binding of radioligand to a single class
of receptor at the concentration used. A representa-
tive saturation isotherm and Scatchard plot is shown
in Figure 1.
The average density (B
receptor in DLPFC
of normal control subjects was 493.3752.7 fmol/mg
protein. The apparent dissociation constant (K
) was
1.1270.10 nM, suggesting a high affinity of the
receptor for the radioligand. All the comparisons
shown below utilized Mann–Whitney U and paired
t’-tests. Greater density of CB
receptor was observed
in the DLPFC of DS (644.6748.8 fmol/mg protein;
24%, Po0.0001) compared with matched controls
(Figure 2). However, there was no difference in the
affinity of receptor for radioligand (DS; 1.1470.08 vs
control; 1.1270.10 nM), suggesting an upregulation of
the density of receptor in the absence of altered
affinity of the receptor. A significant increase (38%,
Po0.001) in CB
receptor immunoreactivity was also
demonstrated by Western blot analysis. A representa-
tive CB
receptor immunoblot of a DS and matched
control (3A) and levels of CB
receptor immunoreac-
tivity of all the subjects (3B) are shown in Figure 3.
receptor-stimulated [
S]GTPgS binding
The CB
receptor-stimulated [
S]GTPgS binding was
used to assess the coupling efficiency between a
receptor and its G-protein. Using the CB
agonist, CP-55,940 stimulated-[
S]GTPgS binding as
the outcome measure, maximum stimulation of
S]GTPgS binding was observed when cortical
membranes were incubated with 1 mM CP-55,940
and 40 mM of GDP (data not shown). The increase in
receptor-stimulated [
S]GTPgS binding was 45%
greater in cortical membranes of DS (31.174.7 fmol/
mg protein; Po0.001) compared with matched con-
trols (16.972.5 fmol/mg protein) (Figure 4). However,
no significant group difference in basal [
binding was observed.
Although our understanding of clinical aspects of
depression has advanced, the precise underlying
neurobiological basis of this disorder remains to be
elucidated. Disturbances in pre- and postsynaptic
proteins in DS have been reported.
A number of
0 100 200 300 400 500 60
Bound / Free
0 1 2 3 4 5
Specific binding (fmol/mg protein)
Figure 1 The saturation binding of [
H]CP-55,940 (0.5–
5.0 nM) to prefrontal cortical membrane of DS and matched
control. The inset represents the Scatchard transformation
of the same binding data.
Density CB
(fmol/mg protein)
Figure 2 The density of CB
receptor was estimated in
prefrontal cortical membranes of DS (10) and matched
controls (10). Data are mean7SEM of two to three experi-
ments, each assayed in duplicate. ***Po0.0001.
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
studies have found differences in serotonergic and
adrenergic receptors in the prefrontal cortex of DS
Recently, Gurevich et al,
suggested that
alterations in the postmodification regulation of gene
expression of serotonin might play a role in the
etiology of major depression. It is likely that the
pathobiology of depression cannot be attributed to
dysfunction in a single neurotransmitter pathway.
Therefore, the search for other neurochemical ab-
normalities associated with depression is continuing.
Recent studies from our laboratory have suggested
the participation of cannabinoidergic system in
alcoholism and related behaviors.
Existence of
comorbidity between alcoholism and depression led
us to investigate the role of cannabinoid signaling in
depression. Indeed, the present study for the first time
reveals greater CB
receptor density and coupling
between these receptors and G
-protein in DLPFC of
DS subjects. CB
receptor immunoblot analysis found
more CB
receptor protein immunoreactivity, sub-
stantiating the radioligand binding results.
Many transmembrane signaling processes of extra-
cellular hormone and neurotransmitters are mediated
by receptor interaction with heterotrimeric (a,b,g)
guanosine nucleotide binding proteins (G-protein).
The receptor activation alters the conformation of
G-proteins leading to the exchange of GDP by GTP
on G
-subunit. The conformational change promotes
the dissociation of G-protein into active G
-GTP and
These two subunits later regulate
the activity of several effector molecules within the
cell. Recently, a nonhydrolyzable GTP analogue,
S]GTPgS, has been employed to asses the coupling
efficacy of several neurotransmitter receptors and G-
proteins in cortical membranes of human postmortem
The results of the present study suggest greater CB
receptor-stimulated [
S]GTPgS binding in DLPFC of
DS compared to matched controls. The observed
increase in [
S]GTPgS binding may be due to more
receptors. Interestingly, we observed low percen-
tage of stimulation of CB
S]GTPgS binding either in DS or matched controls.
Despite the high density of CB
receptors, the reason
for low agonist-stimulated [
S]GTPgS binding is not
known at this time. However, lower efficiency of CB
receptor coupling to G
-protein, compared to other
GPCRs has been suggested.
This is borne out from
direct comparison between the efficacy of cannabi-
noids and opiates in which opiates signaling was
found to be 20-fold more efficient than cannabinoid
Therefore, it is speculated that the CB
receptor signaling functions as a subtle, fine-tuning
mechanism for cells. The high density of receptors
makes the CB
receptor highly sensitive to agonists;
however, the poor coupling efficiency ensures that
overactivation of the system will not occur.
The consequence of elevated CB
signaling in the pathophysiology of depression is not
known. Abnormalities in cAMP signaling in depres-
sive disorders have been reported. Dowlatshahi
receptor immunoreactivity
(Arbitrary number)
Figure 3 (a) A representative immunoblot of the CB
receptor (top) and the same blot was reporbed with a-
tubulin (bottom) to ensure equivalent total protein loading.
(b) Levels of CB
receptor immunoreactivity in prefrontal
cortical membranes of DS (10) and normal controls (10)
reexpressed in mean7SEM of arbitrary densitometric units.
% Stimulation
(fmol/mg protein)
Figure 4 CB
receptor-stimulated [
S]GTPgS binding was
done in prefrontal cortical membranes of DS (10) and
matched controls (10). Data, presented as percentage of
stimulation over the basal, are mean7SEM values of two to
three experiments, each assayed in triplicate. **Po0.001.
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
et al,
found decreased cAMP signaling in the brain
of depressed suicides. The increased CB
density and its mediation in [
S]GTPgS binding
suggest the sensitization of cannabinoidergic signal-
ing, which may lead to the decreased cAMP content
of the cell as these receptors are negatively coupled
to AC.
Recent studies have suggested age-dependent al-
terations in many neurotransmitter receptors. Aged
rats exhibited a marked decrease in CB
receptors and
its mediated [
S]GTPgS binding sites in rat brain.
this study, we also observed (data not shown) reduced
receptor density associated with increasing age in
normal control subject, suggesting that receptor losses
are related to the aging process. This observation is
consistent with previous reports.
Several studies have suggested that age, sex, PMI
and psychoactive drug medications may be respon-
sible for the alterations in neurotransmitter receptors
and G-proteins. The brain samples analyzed in this
study were well matched with regards to sex, age,
ethnic background and postmortem interval. Suicide,
however, is often associated with major depression,
and postmortem studies are often unable to resolve
whether the observed abnormalities are due to the
presence of major depression or whether they reflect
abnormalities that characterize suicidal behavior. In
this study, we are unable to tease out the effect of
suicide vs the effect of depression. Although suicid-
ality is often associated with multiple depressive
symptoms, future studies should test for the differ-
ences between suicide victims with a history of major
depression and nondepressed suicides and or de-
pressed and normal subjects who died by similar
cause of death. The next question whether the
observed abnormalities in DS victims are a conse-
quence of pathobiology or antidepressant medication
is of particular relevance. However, in the present
study, only three patients had medications or alcohol
at the time of death and no psychoactive drugs were
detected in the remaining patients. Therefore, the
present findings in brains of DS are related to the
illness, be it suicide or major depression, rather than
to antemortem drug treatment.
It has been suggested that cannabis use aggravates
existing psychosis.
Two endocannabinoids, which
act on CB receptor, anadamide and palmitoylethano-
lamide, were shown to be increased in the cerebrosp-
inal fluid (CSF) of schizophrenics.
Increased CB
receptor density in the DLPFC of schizophrenia has
also been recently reported.
It has been suggested
that the clinical signs of chronic cannabis consump-
tion may resemble negative symptoms of schizophre-
Several common symptomatologies do exist
between schizophrenia and mood disorders. From a
neuopharmacological standpoint, the psychoses of
schizophrenia and the mania of bipolar disorder can
both be treated with antipsychotic drugs. Some
prominent negative symptoms of schizophrenia such
as affective flattering, alogia and avolition are most
commonly observed in depression.
Therefore, it
may be assumed that the observed elevated CB
receptor and mediated signaling may be a pathologi-
cal consequence of depression and/or schizophrenia.
However, the reported elevation of endocannabinoids
in CSF of schizophrenics
reflects the overall
metabolism of brain, rather than region-specific
alteration. To understand the overall status of the
endocannabinoidergic system in depression and
other psychiatric illnesses, the study on endocanna-
binoid levels in different brain regions is essential
and such studies are currently underway.
Regulation of receptor sensitization and desensiti-
zation is a complex phenomenon. The consequence of
elevated CB
receptor-mediated response observed in
this study is not known. The hyperactivity of
cannabinoidergic signaling could be an adaptive
feedback in response to the decreased levels of
endocannabinoids. The mechanism, physiological
role and regulation of endocannabinoidergic system
are yet to be understood. Recently, it has been shown
that endocannabinoids are involved in retrograde
signaling, and CB
receptor activation suppresses
neurotransmitter release by inhibiting a calcium-
dependent step in vesicle release,
thus decreasing
the local release of synaptic vesicles
However, we
cannot rule out increased endocannabinoid levels,
which, if combined with observed hyperactivity of
receptor-mediated signaling, and hence elevated
retrograde cannabinoidergic neurotransmission in the
pathophysiology of depression or suicidal behavior.
In summary, the upregulation of CB
receptors with
concomitant increase in the CB
S]GTPgS binding strongly suggests a role for the
participation of abnormal endocannabinoidergic neu-
rotransmission in the etiology of depression and
suicide. The pharmacological manipulation of endo-
cannabinoid system may serve as a new therapeutic
target in the treatment of depression.
This study was supported by Grants AA13003 and
NARSAD independent investigator award (BLH);
AA09004 and MH40210 (VA); MH62185 (JJM). The
preliminary findings of this study were presented at
Neuroscience meeting. We thank Dr Veeranna, Centre
for Dementia Research, NKI, for his technical advice.
1 Dewey WL. Cannabinoid pharmacology. Pharmacol Rev 1986; 38:
2 Hollister LE. Health aspects of cannabis. Pharmacol Rev 1986; 38:
3 Abood ME, Martin BR. Neurobiology of marijuana abuse. Trends
Pharmacol Sci 1992; 13: 201–206.
4 Iverson LL. The Science of Marjuana. Oxford University Press: NY,
2000, p 36.
5 Piomelli D, Giuffrida A, Calignano A, Rodriguez de Fonseca F. The
endocannabinoid system as a target for therapeutic drugs. Trends
Pharmacol Sci 2000; 21: 218–224.
6 Pertwee R. Cannabinoids and multiple sclerosis. Pharmacol Ther
2002; 95:165.
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
7 Matsuda LA, Lolait SJ, Brownstein MJ, Young AC, Bonner TI.
Structure of a cannabinoid receptor and functional expression of
the cloned cDNA. Nature 1990; 346: 561–564.
8 Munro S, Thomas KL, Abu-Shaar M. Molecular characterization of
a peripheral receptor for cannabinoids. Nature 1993; 365: 61–65.
9 Devane WA, Hanus L, Breuer A, Pertwee RG, Stevenson LA,
Griffin G et al. Isolation and structure of a brain constituent that
binds to the cannabinoid receptor. Science 1992; 258: 1946–1949.
10 Sugiura T, Konda S, Sukagawa A, Nakane S, Shinoda A, Itoh K et
al. 2-Arachidonoylglycerol: a possible endogenous cannabinoid
receptor ligand in brain. Biochem Biophys Res Commun 1995; 215:
11 Pertwee RG, Stevenson LA, Elrick DB, Mechoulam R, Corbett AD.
Inhibitory effects of certain enantiomeric cannabinoids in the
mouse vas deferens and the myenteric plexus preparation of
guinea-pig small intestine. Br J Pharmacol 1992; 105: 980–984.
12 Kaminski NE, Abood ME, Kessler FK, Martin BR, Schatz AR.
Identification of a functionally relevant cannabinoid receptor on
mouse spleen cells that is involved in cannabinoid-mediated
immune modulation. Mol Pharmacol 1992; 42: 736–742.
13 Howlett AC, Qualy JM, Khachatrian LL. Involvement of G
in the
inhibition of adenylate cyclase by cannabimimetic drugs. Mol
Pharmacol 1986; 29: 307–313.
14 Herkenham M, Lynn AB, Johnson MR, Melvin LS, deCost BR, Rice
KC. Characterization and localization of cannabinoid receptors in
rat brain; a quantitative in vitro autoradiographic study. J Neurosci
1991; 16: 8057–8066.
15 Glass M, Dragunow M, Faull RL. Cannabinoid receptors in the
human brain: a detailed anatomical and quantitative autoradio-
graphic study in the fetal, neonatal and adult human brain.
Neuroscience 1997; 77: 299–318.
16 Westlake TM, Howlett AC, Bonner TI, Matsuda LA, Herkenham M.
Cannabinoid receptor binding and messenger RNA expression in
human brain: an in vitro receptor autoradiography and in situ
hybridization histochemistry study of normal aged and Alzhei-
mer’s brains. Neuroscience 1994; 63: 637–652.
17 Glass M, Faull RL, Dragunow M. A significant loss of cannabinoid
receptors in the substantia nigra in Huntington’s disease. Neu-
roscience 1993; 56: 523–527.
18 Arango V, Underwood MD, Mann JJ. Serotonin brain circuits
involved in major depression and suicide. Prog Brain Res 2002;
136: 443–453.
19 Gonzalez-Maeso J, Rodriguez-Puertas R, Meana JJ, Garcia-Sevilla
JA, Guimon J. Neurotransmitter receptor-mediated activation of G-
proteins in the brains of suicide victims with mood disorders:
selective supersensitivity of a
-adrenoceptors. Mol Psychiatry
2002; 7: 755–767.
20 Dean B, Sundram S, Bradbury R, Scarr E, Copolov D. Studies on
H]CP-55940 binding in the human central nervous system:
regional specific changes in density of cannabinoid-1 receptors
associated with schizophrenia and cannabis use. Neuroscience
2001; 103: 9–15.
21 Basavarajappa BS, Hungund BL. Chronic ethanol increases the
cannabinoid receptor agonist anandamide and its precursor N-
arachidonoylphosphatidyl ethanolamine in SK-N-SH cells.
J Neurochem 1999; 72: 522–528.
22 Basavarajappa BS, Hungund BL. Down-regulation of cannabinoid
receptor agonist-stimulated [
S]GTPgS binding in synaptic plas-
ma membrane from chronic ethanol exposed mouse. Brain Res
1999; 64: 429–436.
23 Hungund BL, Basavarajappa BS, Vadasz C, Kunos G, Rodriguez de
Fonseca F et al. Ethanol, endocannabinoids, and the cannabinoi-
dergic signaling system. Alcohol Clin Exp Res 2002; 26: 565–574.
24 Arango V, Underwood MD, Gubbi AV, Mann JJ. Localized
alterations in pre- and postsynaptic serotonin binding sites in
the ventrolateral prefrontal cortex of suicide victims. Brain Res
1995; 688: 121–133.
25 Kelly TM, Mann JJ. Validity of DSM-III-R diagnosis by psycholo-
gical autopsy: a comparison with antemortem diagnosis. Acta
Psychiatr Scand 1996; 94: 337–343.
26 Lowry OH, Rosebrough NJ, Farr AG, Randall RJ. Protein
measurement with folin phenol reagent. J Biol Chem 1951; 193:
27 Gonzalez-Maeso J, Rodriguez-Puertas R, Gabilondo J, Meana JJ.
Characterization of receptor mediated [
S]GTPgS binding to
cortical membrane from post-mortem human brain. Eur J Pharma-
col 2000; 390: 25–36.
28 Sawada K, Young CE, Barr AM, Longworth K, Takahashi S, Arango
V et al. Altered immunoreactivity of complexin protein in
prefrontal cortex in severe mental illness. Mol Psychiatry 2002;
7: 484–492.
29 Gurevich I, Tamir H, Arango V, Dwork AJ, Mann JJ, Schmauss C.
Altered editing of serotonin 2C receptor pre-mRNA in the
prefrontal cortex of depressed suicide victims. Neuron 2002; 34:
30 Gilman AG. G proteins: transducers of receptor-generated signals.
Ann Rev Biochem 1987; 56: 615–649.
31 Kearn CS, Greenberg MJ, DiCamelli R, Kurzawa K, Hillard CJ.
Relationships between ligand affinities for the cerebellar canna-
binoid receptor CB
and the induction of GDP/GTP exchange.
J Neurochem 1999; 72: 2379–2387.
32 Sim LJ, Selley DE, Childers SR. In vitro autoradiography of
receptor-activated G proteins in rat brain by agonist-stimulated
guanylyl 5
S]thio]-triphosphate binding. Proc Natl
Acad Sci USA 1995; 92: 7242–7246.
33 Dowlatshahi D, MacQueen GM, Wang JF, Reiach JS, Young LT. G
Protein-coupled cyclic AMP signaling in postmortem brain
of subjects with mood disorders: effects of diagnosis, suicide,
and treatment at the time of death. J Neurochem 1999; 73:
34 Romero J, Berrendero F, Garcia-Gil L, de la Cruz P, Ramos JA,
Fernandez-Ruiz JJ. Loss of cannabinoid receptor binding and
messenger RNA levels and cannabinoid agonist-stimulated
O-(thio)-triphosphate binding in the basal ganglia
of aged rats. Neuroscience 1998; 84: 1075–1083.
35 Mann JJ. The neurobiology of suicide. Nat Med. 1998; 1; 25–30.
36 Hollister LE. Health aspect of cannabis: revisited. Int J Neuropsy-
chopharmacol 1998; 1: 71–80.
37 Mathers DC, Ghodse AH. Cannabis and psychotic illness. Br J
Psychiatry 1992; 161: 648–653.
38 Leweke FM, Giuffrida A, Wurster U, Emrich HM, Piomelli D.
Elevated endogenous cannabinoids in schizophrenia. Neuroreport
1999; 10: 1665–1667.
39 Pani L, Gessa GL. The substituted benzamides and their clinical
potential on dysthymia and on the negative symptoms of
schizophrenia. Mol Psychiatry 2002; 7: 247–253.
40 Kupfer DJ, Detre T, Koral J, Fajans PA. Comment on the
‘amotivational syndrome’ in marijuana smokers. Am J Psychiatry
1973; 130: 1319–1321.
41 Kreitzer AC, Regehr WG. Retrograde inhibition of presynaptic
calcium influx by endogenous cannabinoids at excitatory
synapses onto Purkinje cells. Neuron 2001; 29: 717–727.
42 Takahashi KA, Linden DJ. Cannabinoid receptor modulation of
synapses received by cerebellar Purkinje cells. J Neurophysiol
2000; 83: 1167–1180.
43 Kreitzer AC, Regehr WG. Cerebellar depolarization-induced
suppression of inhibition is mediated by endogenous cannabi-
noids. J Neurosci 2001; 21: RC174.
44 Wilson RI, Nicoll RA. Endocannabinoid signaling in the brain.
Science. 2002; 296: 678–682.
receptors-mediated signaling in brain of DS
BL Hungund et al
Molecular Psychiatry
... Several theories of suicide posit that acts of self-injury are reinforcing [5], and dysfunctional endocannabinoid-mediated analgesia may contribute to this process by decreasing mental distress thresholds and enabling frequent coping via SB. Thus, suicidal patients and post-mortem suicide victims display a unique ECS architecture that may contribute to SB pathogenesis [42][43][44][45]. ...
... Notwithstanding the impact that rimonabant had on the biomedical community, there have only been a handful of clinical studies assessing the ECS in suicide patients. In the first post-mortem report comparing lifelong-depressed suicide victims and healthy controls, the dorsolateral prefrontal cortex (DLPFC) of suicide victims showed increased CB1R density and CB1R-stimulated GPCR signalling, but no change in CB1R affinity [42]. These same parameters were greater in both the DLPFC and ventral striatum of alcoholic suicide victims versus non-suicidal chronic alcoholics [43,88]. ...
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Suicide is a devastating complication of psychiatric disorders characterized by despair, hopelessness, and overwhelming mental distress or pain. Non-suicidal self-injury (NSSI), suicide ideation (SI) and suicide attempts (SA) all fall under the umbrella of suicide behaviour (SB). Several biopsychological theories describe SB as an attempt to relieve mental pain. They comment on the role of tolerance-habituation to the rewarding effects of SB-induced emotional regulation, as well as increasing physical or somatic pain tolerance, both of which contribute to the escalating patterns of repetitive SB. The endocannabinoid system (ECS) is involved in a wide range of homeostatic and neuromodulatory functions including appetite/feeding, sleep, motor control, pain perception, cognition, mood/affect, and reward processing. The downregulation of endocannabinoid signalling has major implications for affective disorders, pain disorders, and substance use disorders. SB can be seen as a manifestation of these disorders and has also been linked to ECS dysfunction. Drawing from both animal and human studies, we aim to understand repetitive SB as an endocannabinoid-mediated pain and reward disorder. We hypothesize that mental distress triggers the first incidence of NSSI or SB, from which patients derive stress-induced endocannabinoid-mediated analgesia. As patients become increasingly tolerant to this mechanism of analgesia, SB escalates to override increasing mental distress. This hypothesis calls for more research on endocannabinoid-based therapies to prevent the progression from NSSI or SI to fatal SA.
... Cannabis smoking could alter the prefrontal cortex, which is involved in the development of suicide behavior and thoughts. Even the size of the prefrontal cortex has been associated with the predisposition of cannabis use in adolescence (Wade et al., 2019); researchers have found more CB1 receptors in individuals who died by suicide (Hungund et al., 2004), for the endocannabinoid system is involved in the regulation of psychological process (Le Boisselier et al., 2017) and suicide behaviors (Mannekote Thippaiah et al., 2021). (Mannekote Thippaiah et al., 2021). ...
Background Cannabis is the most frequently consumed drug around the world. Its use has been associated with increased suicide behaviors; nonetheless, the association of cannabis smoking and suicide behaviors in adolescents has not yet been established. The aim of this systematic review and meta-analysis was to evaluate the risk of suicide attempt, suicidal ideation or suicide planning in individuals of 11–21 years of age who smoke cannabis. Methods We performed an online searched using PubMed, EBSCO and Science Direct databases, up to July 2021. We calculated odds ratio with 95% confidence intervals to evaluate the association between suicide attempt, suicidal ideation or suicide planning and cannabis smoking in individuals of 11–21 years of age. Results Twenty studies reported suicide attempts in 34,859 young individuals, suicidal ideation in 26, 937 individuals, and suicide planning in 9054 young individuals. We found an increased risk of suicide attempt in cannabis smokers than in non-cannabis users (OR: 2.33; 95% CI: 1.78–3.05; Z p value; <0.0001; I² = 97.12%), as well as a significant association between cannabis smoking and suicidal ideation (OR: 2.04; 95%CI: 1.64–2.53; Z p value: <0.001; I²: 94.88) and suicide planning (OR: 1.674; 95% CI: 1.554–1.804; Z p value: 0.000; I²: 92.609). Subgroup analyses showed that American teens have an increased risk of suicidal ideation; the meta-regression analysis revealed that age was negatively associated with the risk of suicide attempt. Conclusions This meta-analysis shows that cannabis smoking increased the risk of suicide attempt, suicidal ideation and suicide planning in young individuals of 11–21 years of age. The high risk of suicide behaviors could vary depending on the population studied; therefore, more studies are necessary to corroborate the risk of presenting suicide behaviors in individuals of 11–21 years of age who smoke cannabis.
... Few studies have investigated the endocannabinoid system in postmortem human brain of psychiatric cases. Hungund et al. (238) found that CB1 receptor protein is increased in the dorsolateral PFC of depressed suicides. Moreover, using [35S]GTPgammaS binding assays which assesses coupling of G-proteins to G-proteincoupled receptors in postmortem brain, the authors found that CB1 cannabinoid signaling was increased in the same region when compared to healthy controls (238) implicating cannabinoid signaling in both depression and suicide. ...
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Increasing evidence supports the notion that neuroinflammation plays a critical role in the etiology of major depressive disorder (MDD), at least in a subset of patients. By virtue of their capacity to transform into reactive states in response to inflammatory insults, microglia, the brain’s resident immune cells, play a pivotal role in the induction of neuroinflammation. Experimental studies have demonstrated the ability of microglia to recognize pathogens or damaged cells, leading to the activation of a cytotoxic response that exacerbates damage to brain cells. However, microglia display a wide range of responses to injury and may also promote resolution stages of inflammation and tissue regeneration. MDD has been associated with chronic priming of microglia. Recent studies suggest that altered microglial morphology and function, caused either by intense inflammatory activation or by senescence, may contribute to depression and associated impairments in neuroplasticity. In this context, modifying microglia phenotype by tuning inflammatory pathways might have important translational relevance to harness neuroinflammation in MDD. Interestingly, it was recently shown that different microglial phenotypes are associated with distinct metabolic pathways and analysis of the underlying molecular mechanisms points to an instrumental role for energy metabolism in shaping microglial functions. Here, we review various canonical pro-inflammatory, anti-inflammatory and metabolic pathways in microglia that may provide new therapeutic opportunities to control neuroinflammation in brain disorders, with a strong focus on MDD.
... Studies have found indications of increased CB1r availability in depression. Concentrations of CB1r and CB1rmediated stimulation of G proteins in the PFC were found to be increased in subjects with major depression who had died by suicides relative to controls [178,179]. Similarly, treatment with SSRIs decreased expression of CB1r in the anterior cingulate cortex of postmortem MDD patients [180]. ...
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Depression is characterized by continuous low mood and loss of interest or pleasure in enjoyable activities. First-line medications for mood disorders mostly target the monoaminergic system; however, many patients do not find relief with these medications, and those who do suffer from negative side effects and a discouragingly low rate of remission. Studies suggest that the endocannabinoid system (ECS) may be involved in the etiology of depression and that targeting the ECS has the potential to alleviate depression. ECS components (such as receptors, endocannabinoid ligands, and degrading enzymes) are key neuromodulators in motivation and cognition as well as in the regulation of stress and emotions. Studies in depressed patients and in animal models for depression have reported deficits in ECS components, which is motivating researchers to identify potential diagnostic and therapeutic biomarkers within the ECS. By understanding the effects of cannabinoids on ECS components in depression, we enhance our understanding of which brain targets they hit, what biological processes they alter, and eventually how to use this information to design better therapeutic options. In this article, we discuss the literature on the effects of cannabinoids on ECS components of specific depression-like behaviors and phenotypes in rodents and then describe the findings in depressed patients. A better understanding of the effects of cannabinoids on ECS components in depression may direct future research efforts to enhance diagnosis and treatment.
... Another post-mortem study also suggested a potential role for CB1r in the pathophysiology of depression. This study revealed increased CB1r concentrations and CB1r-mediated G-protein stimulation in the PFC of depressed patients compared to normal individuals [239]. ...
Full-text available
The therapeutic benefits of the current medications for patients with psychiatric disorders contrast with a great variety of adverse effects. The endocannabinoid system (ECS) components have gained high interest as potential new targets for treating psychiatry diseases because of their neuromodulator role, which is essential to understanding the regulation of many brain functions. This article reviewed the molecular alterations in ECS occurring in different psychiatric conditions. The methods used to identify alterations in the ECS were also described. We used a translational approach. The animal models reproducing some behavioral and/or neurochemical aspects of psychiatric disorders and the molecular alterations in clinical studies in post-mortem brain tissue or peripheral tissues were analyzed. This article reviewed the most relevant ECS changes in prevalent psychiatric diseases such as mood disorders, schizophrenia, autism, attentional deficit, eating disorders (ED), and addiction. The review concludes that clinical research studies are urgently needed for two different purposes: (1) To identify alterations of the ECS components potentially useful as new biomarkers relating to a specific disease or condition, and (2) to design new therapeutic targets based on the specific alterations found to improve the pharmacological treatment in psychiatry.
... Bambico et al. [88] reported that at low doses, the CB1R agonist WIN55212-2 exerts potent antidepressant-like properties in the rat FST. An increase of CB1R density in the pre-frontal cortex and concomitant mediated signaling suggest a role of the endocannabinoid system in the etiology of depression [89]. Animal studies based on a mouse model with CB2R deletion in dopamine neurons showed that CB2Rs in dopamine neurons play a role in modulating depression-and anxiety-like behaviors [90,91]. ...
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Antidepressants target a variety of proteins in the central nervous system (CNS), the most important belonging to the family of G-protein coupled receptors and the family of neurotransmitter transporters. The increasing number of crystallographic structures of these proteins have significantly contributed to the knowledge of their mechanism of action, as well as to the design of new drugs. Several computational approaches such as molecular docking, molecular dynamics, and virtual screening are useful for elucidating the mechanism of drug action and are important for drug design. This review is a survey of molecular targets for antidepressants in the CNS and computer based strategies to discover novel compounds with antidepressant activity.
Suicidal behaviour is a public health problem whose magnitude is both substantial and increasing. Since many individuals seek medical treatment following a suicide attempt, strategies aimed at reducing further attempts in this population are a valid and feasible secondary prevention approach. An evaluation of the available evidence suggests that existing treatment approaches have a limited efficacy in this setting, highlighting the need for innovative approaches to suicide prevention. Existing research on the neurobiology of social pain has highlighted the importance of this phenomenon as a risk factor for suicide, and has also yielded several attractive targets for pharmacological strategies that could reduce suicidality in patients with suicidal ideation or a recent attempt. In this paper, the evidence related to these targets is synthesized and critically evaluated. The way in which social pain is related to the “anti-suicidal” properties of recently approved treatments, such as ketamine and psilocybin, is examined. Such strategies may be effective for the short-term reduction in suicidal ideation and behaviour, particularly in cases where social pain is identified as a contributory factor. These pharmacological approaches may be effective regardless of the presence or absence of a specific psychiatric diagnosis, but they require careful evaluation.
Background Recreational use of Delta 8-tetrahydrocannabinol (Delta-8-THC, Δ⁸-THC) has become more common, as are emergency room visits and lasting associated psychiatric conditions associated with Delta-8 (Radwan et al., 2021) (Cannabis (Marijuana) and Cannabinoids 2022). It is essential to recognize the psychoactive effects of Delta-8 as recent exposures are increasing rapidly (Volkow et al., 2014). Physicians must maintain a high index of suspicion for psychosis in relation to use of this compound. We present two cases, a 20-year-old and a 35-year-old, in whom the effects of Delta-8-THC were dramatic and consequential, leading to severe psychosis and lasting depression and suicidal ideation. Conclusions There has been a remarkable increase in the number of emergency department admissions in our hospital and many hospitals that have involved the use of Delta-8-THC. We present these cases to increase physician awareness of Delta-8 (as well as slang terms to describe it like “marijuana-lite” and “diet-weed”) and other legal THC derivatives and the potential side effects so that we can better educate patients and families.
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A potent, synthetic cannabinoid was radiolabeled and used to characterize and precisely localize cannabinoid receptors in slide-mounted sections of rat brain and pituitary. Assay conditions for 3H-CP55,940 binding in Tris-HCl buffer with 5% BSA were optimized, association and dissociation rate constants determined, and the equilibrium dissociation constant (Kd) calculated (21 nM by liquid scintillation counting, 5.2 nM by quantitative autoradiography). The results of competition studies, using several synthetic cannabinoids, add to prior data showing enantioselectivity of binding and correlation of in vitro potencies with potencies in biological assays of cannabinoid actions. Inhibition of binding by guanine nucleotides was selective and profound: Nonhydrolyzable analogs of GTP and GDP inhibited binding by greater than 90%, and GMP and the nonhydrolyzable ATP analog showed no inhibition. Autoradiography showed great heterogeneity of binding in patterns of labeling that closely conform to cytoarchitectural and functional domains. Very dense 3H-CP55,940 binding is localized to the basal ganglia (lateral caudate-putamen, globus pallidus, entopeduncular nucleus, substantia nigra pars reticulata), cerebellar molecular layer, innermost layers of the olfactory bulb, and portions of the hippocampal formation (CA3 and dentate gyrus molecular layer). Moderately dense binding is found throughout the remaining forebrain. Sparse binding characterizes the brain stem and spinal cord. Densitometry confirmed the quantitative heterogeneity of cannabinoid receptors (10 nM 3H-CP55,940 binding ranged in density from 6.3 pmol/mg protein in the substantia nigra pars reticulata to 0.15 pmol/mg protein in the anterior lobe of the pituitary). The results suggest that the presently characterized cannabinoid receptor mediates physiological and behavioral effects of natural and synthetic cannabinoids, because it is strongly coupled to guanine nucleotide regulatory proteins and is discretely localized to cortical, basal ganglia, and cerebellar structures involved with cognition and movement.
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The primary psychoactive ingredient in cannabis, Δ^9-tetrahydrocannabinol (Δ^9-THC), affects the brain mainly by activating a specific receptor (CB1). CB1 is expressed at high levels in many brain regions, and several endogenous brain lipids have been identified as CB1 ligands. In contrast to classical neurotransmitters, endogenous cannabinoids can function as retrograde synaptic messengers: They are released from postsynaptic neurons and travel backward across synapses, activating CB1 on presynaptic axons and suppressing neurotransmitter release. Cannabinoids may affect memory, cognition, and pain perception by means of this cellular mechanism.
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ABSTRACT Agonists stimulate guanylyl 5'- [y-[35S] thiol-triphosphate (GTP[y-35S]) binding to receptor-coupled guanine nucleotide binding protein (G proteins) in cell membranes as revealed in the presence of excess GDP. We now report that this reaction can be used to neuroanatomically localize receptor-activated G proteins in brain sections by in vitro autoradiography of GTP[y-35S] binding. Using the mu opioid-selective peptide [D-Ala2,N-MePhe4,Gly5-ol]enkephalin (DAMGO) as an agonist in rat brain sections and isolated thalamic membranes, agonist stimulation of GTP[y-35S] binding required the presence of excess GDP (1-2 mM GDP in sections vs. 10-30 µM GDP in membranes) to decrease basal G-protein activity and reveal agonist-stimulated GTP[y-35S] binding. Similar concentrations ofDAMGO were required to stimulate GTP[y-35S] binding in sections and membranes. To demonstrate the general applicability of the technique, agonist-stimulated GTP[v-35S] binding in tissue sections was assessed with agonists for the mu opioid (DAMGO), cannabinoid (WIN 55212-2), and y-aminobutyric acid type B (baclofen) receptors. For opioid and cannabinoid receptors, agonist stimulation of GTP[y-35S] binding was blocked by incubation with agonists in the presence of the appropriate antagonists (naloxone for mu opioid and SR-141716A for cannabinoid), thus demonstrating that the effect was specifically receptor mediated. The anatomical distribution of agonist-stimulated GTP[y-35S] binding qualitatively paralleled receptor distribution as determined by receptor binding autoradiography. However, quantitative differences suggest that variations in coupling efficiency may exist between different receptors in various brain regions. This technique provides a method of functional neuroanatomy that identifies changes in the activation of G proteins by specific receptors.
In this paper the historical and scientific background that led to the use of substituted benzamides In two apparently unrelated clinical conditions namely dysthymic disorder and schizophrenia will be reviewed, in order to understand if a common mechanism of action may support this dual therapeutic indication. The dopaminergic antidepressant action of substituted benzamides such as sulpiride, has been proposed, since the late 1970s, by several authors and extensively explored in preclinical experiments by our group. In Italy the first marketing authorization obtained for the new substituted benzamide amisulpride, was with the sole Indication of dysthymia and therefore a solid clinical experience exists in the use of substituted benzamides in mild forms of depression, with more than 1000 000 patients being treated in the last 7 years. The proposed mechanism of action of substituted benzamides Implies a selective modulation of the dopaminergic system in the mesocorticolimbic area, important for cognitive processing of internal and external cues, related to survival. The selective antagonism of dopamine D2-D3 receptors has been evoked to explain, in small to moderate doses (i.e 50-100 mg day(-1)), the antidepressant effect and, in moderate to medium doses (100-400 mg day(-1)), the reported efficacy on negative symptoms of schizophrenia. Thus, substituted benzamides could represent the first class of atypical antipsychotics successfully employed for both depressive states and schizophrenia. Interestingly, recent evidence in the literature suggests that depressive episodes belonging to the bipolar spectrum are among 'alternative indications' of other atypical antipsychotics such as olanzapine and risperidone.