![Effect of bulbectomy and repeated LSD application on [ 35 S]-GTP-gamma-S binding to hippocampal membranes stimulated by various agonists (per cent of basal binding). Note that from the bulbectomy associated anomalies, LSD selectively normalised 5-HT 2 signalling (as induced by alpha-MS). Mean + SEM (n = 4-6); comparison of groups of interest, * p < .05, (NS) = trend (p < .10). Sham = sham-operated rats, bulb = bulbectomised rats; alpha-MS = alpha-methylserotonin.](https://www.researchgate.net/profile/Tobias-Buchborn/publication/262016722/figure/fig2/AS:888733796687872@1588902057778/Effect-of-bulbectomy-and-repeated-LSD-application-on-35-S-GTP-gamma-S-binding-to_Q320.jpg)
Content uploaded by Tobias Buchborn
Author content
All content in this area was uploaded by Tobias Buchborn on May 08, 2020
Content may be subject to copyright.
For Peer Review
Repeated lysergic acid diethylamide (LSD) in an a
nimal
model of depression: Normalisation of learning behaviour
and hippocampal 5-HT
2
signalling
Journal:
Journal of Psychopharmacology
Manuscript ID:
JOP-2013-2161.R1
Manuscript Type:
Original Paper
Date Submitted by the Author:
09-Feb-2014
Complete List of Authors:
Buchborn, Tobias; Otto-von-Guericke University, Institute of Pharmacology
and Toxicology
Schröder, Helmut; Otto-von-Guericke University, Institute of Pharmacology
and Toxicology
Höllt, Volker; Otto-von-Guericke University, Institute of Pharmacology and
Toxicology
Grecksch, Gisela; Otto-von-Guericke University, Institute of Pharmacology
and Toxicology
Please list at least 3 keywords
which relate to your
manuscript::
Serotonergic hallucinogen, 5-HT2A receptor, Animal model of depression,
LSD, Hippocampus
Abstract:
A re-balance of postsynaptic serotonin (5-HT) receptor signalling, with an
increase in 5-HT
1A
and a decrease in 5-HT
2(A)
signalling, is a final common
pathway multiple antidepressants share. Given that the 5-HT
1A/2A
agonist
lysergic acid diethylamide (LSD), when repeatedly applied, selectively
downregulates 5-HT
2(A)
, but not 5-HT
1A
receptors, one might expect LSD to
similarly re-balance the postsynaptic 5-HT signalling. Challenging this idea,
we use an animal model of depression specifically responding to repeated
antidepressant treatment (olfactory bulbectomy), and test the
antidepressant-like properties of repeated LSD (0.13 mg/kg/d, 11d). In
line with former findings, we observe that bulbectomised rats show marked
deficits in active avoidance learning. These deficits, similar as we earlier
noted with imipramine, are largely reversed by repeated LSD. Additionally,
bulbectomised rats exhibit distinct anomalies of monoamine receptor
signalling in hippocampus and/or frontal cortex; from these, only the
hippocampal decrease in 5-HT
2
related [
35
S]-GTP-gamma-S binding is
normalised by LSD. Importantly, the sham-operated rats do not profit from
LSD, and exhibit reduced hippocampal 5-HT
2
signalling. As behavioural
deficits after bulbectomy respond to agents classified as antidepressants
only, we conclude that LSD’s effect in this model can be considered
antidepressant-like, and discuss it in terms of a re-balance of hippocampal
5-HT
2
/5-HT
1A
signalling.
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
For Peer Review
Page 1 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Abstract
A re-balance of postsynaptic serotonin (5-HT) receptor signalling, with an increase in 5-HT
1A
and a
decrease in 5-HT
2(A)
signalling, is a final common pathway multiple antidepressants share. Given that the
5-HT
1A/2A
agonist
lysergic acid diethylamide (LSD), when repeatedly applied, selectively downregulates
5-HT
2(A)
, but not 5-HT
1A
receptors, one might expect LSD to similarly re-balance the postsynaptic 5-HT
signalling. Challenging this idea, we use an animal model of depression specifically responding to
repeated antidepressant treatment (olfactory bulbectomy), and test the antidepressant-like properties of
repeated LSD treatment (0.13 mg/kg/d, 11d). In line with former findings, we observe that bulbectomised
rats show marked deficits in active avoidance learning. These deficits, similar as we earlier noted with
imipramine, are largely reversed by repeated LSD. Additionally, bulbectomised rats exhibit distinct
anomalies of monoamine receptor signalling in hippocampus and/or frontal cortex; from these, only the
hippocampal decrease in 5-HT
2
related [
35
S]-GTP-gamma-S binding is normalised by LSD. Importantly,
the sham-operated rats do not profit from LSD, and exhibit reduced hippocampal 5-HT
2
signalling. As
behavioural deficits after bulbectomy respond to agents classified as antidepressants only, we conclude
that LSD’s effect in this model can be considered antidepressant-like, and discuss it in terms of a re-
balance of hippocampal 5-HT
2
/5-HT
1A
signalling.
Keywords
Serotonergic hallucinogen, LSD, 5-HT
2(A)
receptor, antidepressant, animal model, olfactory bulbectomy,
avoidance learning, hippocampus
Page 2 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Introduction
Lysergic acid diethylamide (LSD) is a serotonergic hallucinogen known to induce profound alterations of
the human consciousness (Hintzen and Passie, 2010). When abused in an unsupervised context,
hallucinogens can have detrimental effects to the individual (Cohen, 1960; Strassman, 1984), when used
in a controlled environment, however, they might be of medical value (Winkelman and Roberts, 2007; De
Lima Osório et al., 2011; Grob et al., 2011). Although early and extensively recognised for their ability to
facilitate certain strategies of psychotherapy (Unger, 1964; Passie, 1997), notably in the context of
anxiety neuroses and/or depressive reactions (Mascher, 1967; Savage et al., 1973), the therapeutic
potential of serotonergic hallucinogens has hardly been considered pharmacologically, i.e. in terms of
their mere receptor profile (Riedlinger and Riedlinger, 1994; Montagne, 2007; Vollenweider and
Kometer, 2010). Sharing the indolethylamine moiety of the serotonin molecule (Kang and Green, 1970),
LSD is a suitable ligand for a variety of monoaminergic, notably serotonergic (5-HT) receptors; with low-
nanomolar affinity, for instance, it binds to 5-HT
1A
and 5-HT
2A
receptors (Roth et al., 2002). Both
receptor subtypes regulate a variety of functions critically involved in the pathogenesis of depression; the
pyramidal integration of excitatory input to the prefrontal cortex (PFC) (Araneda and Andrade, 1991), the
hypothalamic-pituitary-adrenal axis (Zhang et al., 2002; Osei-Owusu et al., 2005), as well as the
hippocampal neurogenesis and/or cell proliferation (Banasr et al., 2004). In accordance with their
functional relevance, long-term treatment with diverse-class antidepressants has been shown to
downregulate 5-HT
2A
receptors in the frontal cortex, and to increase the responsiveness of hippocampal 5-
HT
1A
receptors in a time frame consistent with their delayed therapeutic onset (Haddjeri et al., 1998; Gray
and Roth, 2001; Szabo and Blier, 2001). As repeated LSD, acting as an agonist at both receptor subtypes,
also downregulates 5-HT
2A
, but not 5-HT
1A
receptors (in areas, such as the frontal cortex or the
hippocampus) (Buckholtz et al., 1985, 1990; Gresch et al., 2005), one might expect it to re-balance the
postsynaptic 5-HT signalling in a way similar to antidepressants. And indeed, given that cross-tolerance
Page 3 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
between hallucinogens and antidepressant-class drugs develops (Lucki and Frazer, 1982; Goodwin et al.,
1984; Bonson et al., 1996), a mechanistic overlap seems plausible. Challenging this idea of a mechanistic
overlap, we here evaluate whether LSD exerts antidepressant-like effects within an established animal
model of depression. In the forced swim test, an animal model that responds to one-time antidepressant
application, LSD fails (Gorka et al., 1979). Thus, in line with our assumption that 5-HT
2(A)
regulation
(which requires a repeated LSD regimen) (Buckholtz et al., 1985, 1990) is important for an
antidepressant-like effect to occur, an animal model responding to repeated antidepressant treatment
might be of more validity. From the few animal models, which meet such a criterion, we here decide for
the olfactory bulbectomy because it is the only one considered highly reliable and specific (Jesberger and
Richardson, 1985; Cryan et al., 2002). Following the bilateral dissection of the olfactory bulbs, rodents
show a variety of behavioural disturbances, such as stress-associated hyperlocomotion or avoidance
learning deficits, which reliably ameliorate in response to the (sub-)chronic, but not acute application of
drugs specified as antidepressants (Kelly et al., 1997; Song and Leonard, 2005). The bulbectomy induced
hyperlocomotion is considered to be of dopaminergic origin (Masini et al., 2004) and might model
symptoms of the agitated depression. Avoidance learning deficits, on the other hand, involve the
serotonin system (Cairncross et al., 1979; Garrigou et al., 1981; Ögren 1986) and appear to have more
general implications for the human situation. According to the cognitive theory, depression primarily
arises from biases in cognitive processing, including attention and memory, which as a consequence
corrupt emotional integrity (e.g. Mathews and MacLeod, 2004). As (serotonergic) antidepressants are
thought to act on these biases, rather than on mood itself (Harmer, 2008; Harmer et al., 2009), avoidance
learning deficits of bulbectomised rats seem to be an optimal proxy for depressive-like cognition biases
and their responsiveness to serotonin related action of antidepressant-class drugs.
Thus, for evaluating the antidepressant-like action of LSD, we here repeatedly apply the hallucinogen to
bulbectomised rats and investigate its effect on avoidance learning and forebrain 5-HT
1A
/5-HT
2
Page 4 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
signalling. As LSD, despite having high affinity, is not selective for 5-HT
1A
and 5-HT
2(A)
receptors (Roth
et al., 2002), we additionally investigate its effect on beta, overall 5-HT, dopamine and noradrenaline
signalling. Methodologically, we use the conditioned pole-jumping paradigm and radioligand binding
techniques, respectively.
Methods and Materials
Animals and housing
For experiments, male Wistar rats (Ø 400 g) (HsdCpb:WU; Harlan Winkelmann, Germany) were used.
The animals were housed in groups of five each cage, and held under controlled laboratory conditions
(temperature 20 ± 2 °C, air humidity 55-60%, light/dark cycle 12:12 [light on at 6 a.m.]) with standard
food pellets (TEKLAD Global Diet, Harlan-Teklad, UK) and tap water ad libitum. All experiments
conducted comply with the regulations of the National Act on the Use of Experimental Animals
(Germany), as approved by the Tierschutzkommission Sachsen-Anhalt.
Bilateral olfactory bulbectomy
At the age of seven weeks, rats were bulbectomised as described by Grecksch et al. (1997). In brief,
animals were anaesthetised with pentobarbital (40 mg/kg i.p. [10 ml/kg injection volume]) and fixed in a
stereotactic instrument. The scalp was incised at the midline, and two holes (Ø 2 mm) were drilled into
the skull (one above each olfactory bulb [6.5 mm anterior to bregma, 2 mm lateral to midline]). The bulbs
were cut and gently removed by aspiration. The resulting cavities were filled with haemostatic sponges
(Gelitaspon®, Gelita Medical, The Netherlands), and the skin was closed by tissue adhesive
(Histoacryl®, Braun Aesculap AG, Germany). Extent and adequacy of the surgical ablation were assessed
after decapitation at end of the behavioural experiments. Sham-operated rats were treated alike (including
piercing of dura mater), except that their bulbs were not removed.
Page 5 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Behavioural experiments
Treatment.
Lysergide[(R,R)-tartrate]-anhydrate (THC Pharm, Germany) was applied for a period of 11
days, once every 24 hours (0.13 mg/kg, s.c., dissolved in isotonic saline, 10 ml/kg). Treatment started five
days before the behavioural experiments, and continued till 24 hours before decapitation. The dose
chosen was extrapolated from literature as adequate for activation of 5-HT
2A
receptors (as indexed by the
occurrence of wet dog shakes) (Bedard and Pycock, 1977). The five days beforehand regimen was chosen
so to allow 5-HT
2A
(down-)regulation to precede the behavioural experiments (Buckholtz et al., 1990). To
avoid interference from LSD’s acute effects (Taeschler et al., 1960; Schmidt, 1963; Domino et al., 1965;
Bignami, 1972), administration was performed two hours after each test session (Castellano, 1979).
Control animals received saline injections without LSD.
Assignment of rats to conditions (sham/saline vs. sham/LSD; bulb/saline vs. bulb/LSD) occurred in a
randomised fashion.
One-way active avoidance learning (pole-jumping test).
Eight weeks after surgery, on the
sixth day of subchronic treatment, pole-jumping experiments set in. On five days in a row, within ten
trials each day, rats had to learn to actively avoid electrical foot stimuli (unconditioned stimulus [US]) by
jumping onto a pole. Every trial started with a sound from a buzzer (80 dB) (conditioned stimulus [CS]),
which –from second four on– was accompanied by the electrical foot stimulation (delivered through
stainless steel rods of the test apparatus’ floor, and adjusted to the rat’s individual pain sensitivity [0.2-0.4
mA]). A trial was restricted to 20 seconds, but stopped earlier when a rat successfully jumped onto the
pole. CS and US overlapped and were co-terminated. The intertrial-interval was stochastically varied (30-
90 s). All five sessions were performed at about the same time during the light period. On the first day,
rats were allowed five minutes for exploration of the test apparatus, on the following days only one
Page 6 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
minute was granted. For evaluation of learning, the number of successful escapes (instrumental reactions,
≤ 20 s) and avoidances (conditioned reactions, ≤ 4 s) was recorded.
Neurochemical experiments
5-HT
2A
receptor binding.
Twenty-four hours after the last treatment, rats were decapitated, brain
regions of interest (frontal cortices and hippocampi) were removed and frozen in liquid nitrogen. For
measuring ketanserin-sensitive [
3
H]spiroperidol binding to 5-HT
2A
receptors, thawed tissue was
homogenised. Cell membranes were pelleted by centrifugation (10 min, 50,000 x g, 4 °C), washed in Tris
buffer (pH 8.0), and resuspended in incubation buffer (50 mM Tris-HCI, containing 120 mM NaCl, 5 mM
KCl, 2.5 mM CaCl
2
, 1 mM MgCl
2
, and 50 nM d-butaclamol [D
2
receptor mask] [Sigma-Aldrich,
Germany], pH 8.0). Aliquots of the crude membrane suspension (150-250 µg protein) were incubated for
30 minutes at 37 °C with [
3
H]spiroperidol (specific activity: 800 GBq/mM [Perkin-Elmer, USA]). The
membrane fraction was then collected on GF/A glass-fibre filters, washed with buffer (50 mM Tris-HCl,
pH 8.0), and a taken for liquid scintillation counting in a toluene containing scintillation cocktail. Specific
binding was calculated by subtracting non-specific binding (as seen in presence of 0.25 nM
[
3
H]spiroperidol and 1 µM unlabelled ketanserin [Sigma-Aldrich, Germany]) from total binding (obtained
with 0.25 nM [
3
H]spiroperidol alone), and expressed in fmol per mg of protein (as determined by Lowry
Method).
[
35
S]-GTP-gamma-S binding.
For measuring G-protein coupling by 5-HT
(1A/2)
, dopamine, and (beta)
adrenergic receptors, tissue was homogenised in Tris buffer (50 mM Tris-HCl, 1 mM EGTA, 10 mM
EDTA, pH 7.4) and pelleted by centrifugation. After resuspension in assay buffer (50 mM Tris-HCl, 3
mM MgCl
2
, 0.2 mM EGTA, 100 mM NaCl, pH 7.4), aliquots containing 15-20 µg protein were incubated
with 3 µM GDP and 0.05 nM [
35
S]-GTP-gamma-S (specific activity: 46.3 TBq/mM [Perkin-Elmer,
Page 7 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
USA]) in presence and absence of the relevant agonist (1h, 30 °C) (10 µM alpha-methylserotonin [alpha-
MS for 5-HT
2
], 100 µM 8-hydroxy-2-[di-n-propylamino] tetralin [8-OH-DPAT for 5-HT
1A
], 100 µM
isoprenaline [for beta], 10 µM serotonin, 100 µM dopamine, and 10 µM noradrenaline [Sigma-Aldrich,
Germany]). Incubation was terminated by rapid filtration, filters were rinsed in washing buffer (50 mM
Tris-HCl, 3 mM MgCl
2
, 1 mM EGTA, pH 7.4), and taken for liquid scintillation counting of bound
radioactivity. Total [
35
S]-GTP-gamma-S binding was corrected for unspecific binding (in presence of 10
µM unlabelled GTP-gamma-S), and expressed as E
max
, percent stimulation over basal specific binding.
All determinations were performed at least in duplicate.
Statistical analysis
A two-factor ANOVA with repeated measures on one factor (mixed model) was conducted to assess main
effects and interaction of time and group in avoidance learning, and followed by pairwise contrast
analysis. Intergroup differences in specifically bound radioactivity were analysed using nonparametric
Mann-Whitney U-tests (a-priori planned comparisons). Calculations were carried out by SPSS and
GraphPad Prism software. Statistical significance was assumed if the null hypothesis could be rejected at
.05 probability level.
Results
Behavioural experiments
The omnibus F-test revealed significant main effects for both factors, time (F
[4, 124]
= 69.04, p =.000
[conditioned]; F
[4, 124]
= 43.22, p =.000 [instrumental]) and group (F
[3, 31]
= 6.39, p = .002 [conditioned];
F
[3, 31]
= 2.93, p = .049 [instrumental]), and a significant time x group interaction for conditioned reactions
(F
[12, 124]
= 2.62, p = .004). Results were further probed by pairwise comparison with a-priori specified
contrasts. As can be seen in Figure 1, sham-operated rats showed good progress in learning instrumental
Page 8 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
and conditioned avoidance behaviour. Irrespective of treatment, they rapidly learnt to avoid and/or to
escape from the aversive foot stimuli (sham/saline vs. sham/LSD: F
[1, 17]
= .08, p = .78 [conditioned]; F
[1,
17]
= .963, p = .34 [instrumental]). Saline treated bulbectomised rats failed to achieve the level of
performance shown by the sham-operated controls; the acquisition of both, the conditioned and
instrumental reactions, was disturbed (sham/saline vs. bulb/saline: F
[1, 14]
= 13.15, p = .003 [conditioned];
F
[1, 14]
= 4.85, p = .045 [instrumental]). The repeated administration of LSD, however, led to a
normalisation of conditioned avoidance learning: LSD treated bulbectomised rats caught up with the
sham-operated controls (sham/saline vs. bulb/LSD: F
[1, 16]
= 2.16, p = .16), and significantly differed from
their saline treated counterparts (bulb/saline vs. bulb/LSD: F
[4, 56]
= 2.6, p = .045) (Figure 1 [a]). As to the
instrumental reactions, LSD treated bulbectomised rats did not significantly differ from the sham-
operated controls (sham/saline vs. bulb/LSD: F
[1, 16]
= .813, p = .38), the difference from the saline treated
bulbectomised animals, however, failed to achieve statistical significance (see Figure 1 [b]) (bulb/saline
vs. bulb/LSD: F
[4, 56]
= .766, p = .55).
[Figure 1 near here]
Neurochemical experiments
5-HT
2A
receptor binding.
As shown in Figure 2, bulbectomy slightly increased the ketanserin-
sensitive [
3
H]spiroperidol binding in hippocampus. This trend of increase (sham/saline vs. bulb/saline: u
= 4, p = .095) was partially counteracted by the repeated LSD treatment. Although the difference between
LSD and saline treated bulbectomised rats fell short of significance (bulb/saline vs. bulb/LSD: u = 6, p =
.063), the difference between LSD treated bulbectomised rats and saline treated, sham-operated controls
was not significant either (sham/saline vs. bulb/LSD: u = 11, p = .46). As opposed to its decreasing effect
in bulbectomised rats, repeated LSD treatment did not affect the hippocampal [
3
H]spiroperidol/ketanserin
Page 9 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
binding of the sham-operated animals (sham/saline vs. sham/LSD: u = 11, p = .46). In the frontal cortex,
bulbectomy had no significant effect on the ketanserin-sensitive [
3
H]spiroperidol binding (sham/saline vs.
bulb/saline: u = 9, p = .27); LSD, however, induced a significant increase (sham/saline vs. sham/LSD: u =
0, p = .002) (Figure 2).
[Figure 2 near here]
[
35
S]-GTP-gamma-S binding.
In the hippocampus, bulbectomy led to a significant reduction in
alpha-MS stimulated guanine nucleotide exchange (sham/saline vs. bulb/saline: u = 5, p = .041) which
was reversed by subchronic LSD (bulb/saline vs. bulb/LSD: u = 6, p = .032) (Figure 3). In contrast to its
resensitising effect in bulbectomised rats, LSD caused a desensitisation of alpha-MS stimulated [
35
S]-
GTP-gamma-S binding in the hippocampus of the sham-operated animals (sham/saline vs. sham/LSD: u
= 3, p = .0015). Other significant effects and/or trends of bulbectomy, such as the hippocampal decrease
in isoprenaline and noradrenaline stimulated receptor signalling (sham/saline vs. bulb/saline: u = 0, p =
.004; u = 2, p = .057), or the fronto-cortical increase in alpha-MS, 8-OH-DPAT, and isoprenaline induced
[
35
S]-GTP-gamma-S binding (sham/saline vs. bulb/saline: u = 4, p = .026; u = 2, p = .016; u = 1, p = .036)
were not reversed by LSD (Figure 3 and 4). The hippocampal signalling stimulated by 8-OH-DPAT,
serotonin, and dopamine was neither influenced by bulbectomy (sham/saline vs. bulb/saline: u = 15, u =
18, and u = 8, respectively, n. s.), nor by its interaction with repeated LSD (bulb/saline vs. bulb/LSD: u =
14.5, u = 15.5, and u = 16, n. s.) (Figure 3). Finally, in the frontal cortex of the sham-operated animals,
LSD led to a sensitisation of all receptors investigated, including 5-HT
2
(sham/saline vs. sham/LSD: u =
3.5, p = .022) (Figure 4).
[Figure 3 near here] [Figure 4 near here]
Page 10 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Discussion
Exploratory evidence suggests that serotonergic hallucinogens –when psychotherapeutically embedded–
might be assistant to the treatment of neurotic-type depression (Mascher, 1967; Savage et al., 1973), or
emotional distress associated with advanced stages of cancer (Kurland et al., 1973; Grob et al., 2011). As
their acute effects on affection are highly fluctuant and critically dependent on the pre-existing mood,
though (Metzner et al., 1963; Katz et al., 1968), hallucinogens should not be (mis-)conceptualised as
acute mood-enhancers or antidepressants in a literal sense. Instead, they might rather be seen as a tool for
psychotherapy to facilitate access to emotion-salient cognitions (e.g. memory) and work on the inherent
biases that negatively prime the patient’s affective mindset (compare Kurland et al., 1973; Harmer, 2008;
Carhart-Harris et al., 2012). Here, we refer to the idea that hallucinogens –similar as hypothesised
relevant for repeated antidepressant treatment (Gray and Roth, 2001; Harmer, 2008; Savitz et al., 2009)–
might affect mood-relevant cognitive biases by regulation of 5-HT
1A/2(A)
receptors. We repeatedly apply
LSD to bulbectomised rats, and test its effect on depressive-like avoidance learning deficits and forebrain
5-HT
1A/2
signalling. In keeping with former findings (Marks et al., 1971; Thomas, 1973; Cairncross et al.,
1979; Gebhardt et al., 2013), we confirm that bulbectomised rats are deficient in active avoidance
learning. Similar as we earlier noted with imipramine under comparable experimental conditions
(Grecksch et al., 1997), or as noted by other labs with amitriptyline or trazodone (Cairncross et al., 1973;
Otmakhova et al., 1992), repeated LSD treatment –in dosing known to induce 5-HT
2A
related wet dog
shakes (Bedard and Pycock, 1977)– largely reverses this deficiency. As the avoidance learning deficits
after bulbectomy are reversible by drugs classified as antidepressant only (Kelly et al., 1997), we infer
that LSD’s behavioural effect in this model can be considered antidepressant-like. Our inference is
strengthened by the fact that LSD specifically helps bulbectomised, but not sham-operated rats.
In addition, we show that bulbectomised rats exhibit various anomalies of monoamine receptor signalling,
with 5-HT
1A
, 5-HT
2
and beta signalling being sensitised in the frontal cortex, and the latter two being
Page 11 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
desensitised in the hippocampus. From the given anomalies, the desensitisation of hippocampal 5-HT
2
signalling, as indicated by a decrease in alpha-MS stimulated [
35
S]-GTP-gamma-S binding, is the only to
be normalised by subchronic LSD. Despite alpha-MS being a mixed 5-HT
1/2
agonist (Ismaiel et al., 1990)
rather than selective for 5-HT
2
receptors, we think 5-HT
2
receptors might be more implicated, because
neither bulbectomy nor its interaction with LSD significantly influences hippocampal 5-HT
1A
signalling.
Also, the relevance of hippocampal 5-HT
2(A)
receptors might be inferred from our finding that bulbectomy
is associated with trends for increased ketanserin-sensitive [
3
H]spiroperidol binding, and LSD to
counteract it. Although these trends should be interpreted with caution, they yet are reminiscent on former
findings about bulbectomy upregulating, and/or antidepressants downregulating hippocampal 5-HT
2
receptors (Gurevich et al., 1993; Earley et al., 1994). Hippocampal 5-HT
2(A)
anomalies might be a
consequence of the bulbectomy induced raphe degeneration (Nesterova et al., 1997), and the (associated)
reduction in local serotonin (van der Stelt et al. 2005). Remarkably, similar as seen for the avoidance
learning deficiency, LSD’s (counter-)regulatory action on 5-HT
2(A)
receptors
is specific for the
pathological condition; in sham-operated animals, it desenitises alpha-MS signalling, and leaves
ketanserin-sensitive [
3
H]spiroperidol binding unaffected.
LSD exhibits high 5-HT
1A
and
2A
affinity, but it is not selective for these receptors. In fact, it binds to a
variety of monoamine receptors (Roth et al., 2002), with beta and D
4
, for instance, complementing 5-
HT
2A
in LSD’s behavioural profile (Mittman and Geyer, 1991; Marona-Lewicka et al., 2009). As neither
bulbectomy nor its interaction with LSD, however, affects overall dopamine signalling, and LSD
normalises hippocampal 5-HT
2
, but not beta signalling, we think it is reasonable to discuss the LSD
induced normalisation of avoidance learning in terms of a re-balance of hippocampal 5-HT
2
(vs.
1A
)
signalling. Deficits in avoidance learning as well as their reversal by antidepressants have been linked to
5-HT
2(A)
receptors (Broekkamp et al. 1980; Gurevich et al. 1993; Ögren 1986), and LSD is known to
affect learning via hippocampal 5-HT
2A
regulation (Romano et al., 2010). Bulbectomy leads to deficient
Page 12 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
hippocampal neurogenesis, and to an upregulation of brain-derived neurotrophic factor (BDNF) (Jaako-
Movits and Zharkovsky, 2005; Hellweg et al., 2007). Although generally considered antidepressant-like,
too much BDNF might be detrimental and compromise avoidance learning (Croll et al., 1999). As a
model of LSD’s antidepressant-like activity one could, therefore, hypothesise that LSD (by activating 5-
HT
1A
and resensitising 5-HT
2
signalling) might re-balance the anti-BDNF effect of 5-HT
2A
against the
neurotrophic effect of 5-HT
1A
receptors (Vaidya et al., 1999; Santarelli et al., 2003). Consequently, a
more coordinated turnover of hippocampal neurons might occur, allowing the stress-integration system of
bulbectomised rats to more effectively meet the demands of avoidance learning (compare Sairanen et al.,
2005; Surget et al., 2011). This model is speculative, however, and needs further investigation. Also, to
more clearly establish the role of 5-HT
2(A)
and
1A
receptors, future research might co-apply selective
antagonists with LSD, combine a selective 5-HT
1A
with a selective 5-HT
2(A)
agonist, or use selective dual
agonists instead. As the latter seem sparse (Ray, 2010), the repeated combination of two agents will raise
pharmacokinetic problems, and 5-HT
2(A)
antagonists act antidepressant-like themselves (e.g. Otmakhova
et al., 1992), such a study might be complicated, though.
Intriguingly in the frontal cortex of the sham-operated rats, LSD significantly increases all binding
parameters investigated (including those of 5-HT
2[A]
), which in bulbectomised animals –for the most
part– cannot be found. Likewise in hippocampus, the desensitisation of 5-HT
2
and dopamine signalling
specifically occurs in the sham rats. Our results contrast with the notion that LSD selectively
downregulates 5-HT
2(A)
receptors (Buckholtz et al., 1985, 1990). Yet, possibly varying with application
scheme, strain, and/or embedding of the rats into behavioural procedures, hallucinogens might provoke a
more or less complex pattern of receptor regulation (e.g. 5-HT
1A
downregulation for psilocybin, alpha
1
upregulation for DOI, or regional 5-HT
2A
down- vs. upregulation for DOM) (Buckholtz et al., 1988,
1990; Doat-Meyerhoefer et al., 2005). The fact that LSD –despite regulating their neurochemistry– does
not affect avoidance learning of the sham rats, underlines that our application scheme was well chosen.
Page 13 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Repeatedly applying LSD –such as noted for antidepressant-class drugs– might have counteracted the
neurochemical imbalance induced by bulbectomy (including hippocampal 5-HT
2
signalling), thus,
normalising the learning capacity (or re-shifting the cognitive bias) of the bulbectomised rats. For the
sham animals, as opposed, there had never been such an imbalance (or bias), and the only (or most likely)
way in which LSD might have affected their avoidance learning would have been by acutely interfering.
Applying LSD two hours after each learning session, however, we minimised the chance of such an
interference (compare Castellano, 1979; Frieder and Allweis, 1982). Therefore, the LSD induced changes
of the sham rats’ neurochemistry might rather be unspecific and (temporally) unrelated to the processes
involved in avoidance learning.
In summary, our data demonstrate that in bulbectomised rats, repeated LSD treatment reverses
depressive-like avoidance learning deficits, possibly engaging a re-balance of hippocampal 5-HT
2
(vs.
1A
)
signalling. Given the postulated interrelation between the reversal of mood-relevant cognitive biases and
5-HT
(2A)
receptor regulation (Harmer, 2008), our findings might have implications for the understanding
of how hallucinogens alleviate emotional distress, such as seen in advanced-stage cancer.
Acknowledgements
The professional technical assistance of Michaela Böx, Petra Dehmel, Doreen Heidemann, and Gabriele
Schulze is gratefully acknowledged.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-
profit sectors.
Conflict of Interest Statement
The authors declare that there is no conflict of interest.
Page 14 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Reference
Araneda R, Andrade R (1991) 5-Hydroxytryptamine2 and 5-hydroxytryptamine1A receptors mediate
opposing responses on membrane excitability in rat association cortex. Neuroscience 40: 399-412.
Banasr M, Hery M, Printemps R, et al. (2004) Serotonin-Induced Increases in Adult Cell Proliferation and
Neurogenesis are Mediated Through Different and Common 5-HT Receptor Subtypes in the Dentate
Gyrus and the Subventricular Zone. Neuropsychopharmacology 29: 450-460.
Bedard P, Pycock C J (1977) ‘Wet-Dog’ shake behaviour in the rat: A possible quantitative model of
central 5-hydroxytryptamine activity. Neuropharmacology 16: 663-670.
Bignami G (1972) Facilitation of avoidance acquisition by LSD-25. Psychopharmacologia 25: 146-151.
Bonson K R, Buckholtz J W, Murphy D L (1996) Chronic Administration of Serotonergic
Antidepressants Attenuates the Subjective Effects of LSD in Humans. Neuropsychopharmacology
14: 425-436.
Broekkamp C L, Garrigou D, Lloyd KG (1980) Serotonin-mimetic and antidepressant drugs on passive
avoidance learning by olfactory bulbectomised rats. Pharmacol Biochem Behav 13: 643-646.
Buckholtz N S, Freedman D X, Middaugh L D (1985) Daily LSD administration selectively decreases
serotonin2 receptor binding in rat brain. Eur J Pharmacol 109: 421-425.
Buckholtz N. S., Zhou D. F., Freedman D. X. (1988). Serotonin2 agonist administration down-regulates
rat brain serotonin2 receptors. Life Sci, 42, 2439-2445.
Buckholtz N S, Zhou D F, Freedman D X, et al. (1990) Lysergic acid diethylamide (LSD) administration
selectively downregulates serotonin2 receptors in rat brain. Neuropsychopharmacology 3: 137-148.
Cairncross K D, Cox B, Forster C, et al. (1979) Olfactory projection systems, drugs and behaviour: A
review. Psychoneuroendocrinology 4: 253-272.
Cairncross K D, Schofield S, King H G (1973) The Implication of Noradrenaline in Avoidance Learning
in the Rat. Prog Brain Res 39: 481-485.
Carhart-Harris R L, Leech R, Williams T M, et al. (2012) Implications for psychedelic-assisted
psychotherapy: functional magnetic resonance imaging study with psilocybin. Br J Psychiatry 200:
238-244.
Castellano C (1979) Effects of LSD-25 on avoidance behavior and locomotor activity in mice.
Psychopharmacology 62: 145-149.
Cohen S (1960) Lysergic Acid Diethylamide: Side Effects and Complications. J Nerv Ment Dis 130: 30-
40.
Croll S D, Suri C, Compton D L, et al. (1999) Brain-derived neurotrophic factor transgenic mice exhibit
passive avoidance deficits, increased seizure severity and in vitro hyperexcitability in the
hippocampus and entorhinal cortex. Neuroscience 93: 1491-1506.
Cryan J F, Markou A, Lucki I (2002) Assessing antidepressant activity in rodents: recent developments
and future needs. Trends Pharmacol Sci 23: 238-245.
De Lima Osório F, de Macedo L R H, de Sousa J P M, et al. (2011) The therapeutic potential of harmine
and ayahuasca in depression: Evidence from exploratory animal and human studies. In Dos Santos
RG (ed) The Ethnopharmacology of Ayahuasca. Transworld Research Network, Kerala.
Doat-Meyerhoefer M M, Hard R, Winter J C, et al. (2005) Effects of clozapine and 2,5-dimethoxy-4-
methylamphetamine [DOM] on 5-HT2A receptor expression in discrete brain areas. Pharmacol
Biochem Behav 81: 750-757.
Domino E, Caldwell D, Henke R (1965) Effects of psychoactive agents on acquisition of conditioned pole
jumping in rats. Psychopharmacologia 8: 285-289.
Earley B, Glennon M, Lally M, et al. (1994) Autoradiographic distribution of cholinergic muscarinic
receptors and serotonin2 receptors in olfactory bulbectomized (OB) rats after chronic treatment with
mianserin and desipramine. Hum Psychopharmacol 9: 397-407.
Page 15 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Frieder B, Allweis C (1982) Memory consolidation: Further evidence for the four-phase model from the
time-courses of diethyldithiocarbamate and ethacrinic acid amnesias. Physiol Behav 29: 1071-1075.
Garrigou D, Broekkamp C L, Lloyd K G (1981) Involvement of the amygdala in the effect of
antidepressants on the passive avoidance deficit in bulbectomised rats. Psychopharmacology 74: 66-
70.
Gebhardt N, Bär K-J, Boettger M K, et al. (2013) Vagus nerve stimulation ameliorated deficits in one-
way active avoidance learning and stimulated hippocampal neurogenesis in bulbectomized rats.
Brain Stimulat 6: 78-83.
Goodwin G M, Green A R, Johnson P (1984) 5-HT2 receptor characteristics in frontal cortex and 5-HT2
receptor-mediated head-twitch behaviour following antidepressant treatment to mice. Br J
Pharmacol 83: 235-242.
Gorka Z, Wojtasik E, Kwiatek H, et al. (1979) Action of serotoninmimetics in the behavioral despair test
in rats. Commun Psychopharmacol 3: 133-136.
Gray J A, Roth B L (2001) Paradoxical trafficking and regulation of 5-HT2A receptors by agonists and
antagonists. Brain Res Bull 56: 441-451.
Grecksch G, Zhou D, Franke C, et al. (1997) Influence of olfactory bulbectomy and subsequent
imipramine treatment on 5-hydroxytryptaminergic presynapses in the rat frontal cortex: behavioural
correlates. Br J Pharmacol 122: 1725-1731.
Gresch P J, Smith R L, Barrett R J, et al. (2005) Behavioral Tolerance to Lysergic Acid Diethylamide is
Associated with Reduced Serotonin-2A Receptor Signaling in Rat Cortex.
Neuropsychopharmacology 30: 1693-1702.
Grob C S, Danforth A L, Chopra G S, et al. (2011) Pilot study of psilocybin treatment for anxiety in
patients with advanced-stage cancer. Arch Gen Psychiatry 68: 71-78.
Gurevich E V, Aleksandrova I A, Otmakhova N A, et al. (1993) Effects of bulbectomy and subsequent
antidepressant treatment on brain 5-HT2 and 5-HT1A receptors in mice. Pharmacol Biochem Behav
45: 65-70.
Haddjeri N, Blier P, de Montigny C (1998) Long-term antidepressant treatments result in a tonic
activation of forebrain 5-HT1A receptors. J Neurosci 18: 10150-10156.
Harmer C J (2008) Serotonin and emotional processing: Does it help explain antidepressant drug action?
Neuropharmacology 55: 1023-1028.
Harmer C J, Goodwin G M, Cowen P J (2009) Why do antidepressants take so long to work? A cognitive
neuropsychological model of antidepressant drug action. Br J Psychiatry 195: 102-108.
Hellweg R, Zueger M, Fink K, et al. (2007) Olfactory bulbectomy in mice leads to increased BDNF
levels and decreased serotonin turnover in depression-related brain areas. Neurobiol Dis 25: 1-7.
Hintzen A, Passie T (2010) The pharmacology of LSD: a critical review. Oxford University Press, New
York.
Ismaiel A M, Titeler M, Miller K J, et al. (1990) 5-HT1 and 5-HT2 binding profiles of the serotonergic
agents .alpha.-methylserotonin and 2-methylserotonin. J Med Chem 33: 755-758.
Jaako-Movits K, Zharkovsky A (2005) Impaired fear memory and decreased hippocampal neurogenesis
following olfactory bulbectomy in rats. Eur J Neurosci 22: 2871-2878.
Jesberger J A, Richardson J S (1985) Animal models of depression: Parallels and correlates to severe
depression in humans. Biol Psychiatry 20: 764-784.
Katz M M, Waskow I E, Olsson J (1968) Characterizing the psychological state produced by LSD. J
Abnorm Psychol 73: 1-14.
Kang S, Green J P (1970) Steric and Electronic Relationships among Some Hallucinogenic Compounds.
Proc Natl Acad Sci U S A 67: 62-67.
Kelly J P, Wrynn A S, Leonard B E (1997) The olfactory bulbectomized rat as a model of depression: An
update. Pharmacol Ther 74: 299-316.
Page 16 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Kurland A A, Grof S, Pahnke W N, et al. (1973) Psychedelic Drug Assisted Psychotherapy in Patients
with Terminal Cancer. In Goldberg I K, Malitz S, Kutscher A H (eds), Psychopharmacological
agents for the terminally ill and bereaved. Columbia University Press, London.
Lucki I, Frazer A (1982) Prevention of the serotonin syndrome in rats by repeated administration of
monoamine oxidase inhibitors but not tricyclic antidepressants. Psychopharmacology 77: 205-211.
Marks H E, Remley N R, Seago J D, et al. (1971) Effects of bilateral lesions of the olfactory bulbs of rats
on measures of learning and motivation. Physiol Behav 7: 1-6.
Marona-Lewicka D, Chemel B R, Nichols D E (2009) Dopamine D4 receptor involvement in the
discriminative stimulus effects in rats of LSD, but not the phenethylamine hallucinogen DOI.
Psychopharmacology (Berl) 203: 265-277.
Mascher E (1967) Psycholytic therapy: Statistics and indications. In Brill H, Cole JO (eds), Neuro-
psycho-pharmacology. Proceedings of the 5th international congress. Excerpta medica, Amsterdam.
Masini C V, Holmes P V, Freeman K G, et al. (2004) Dopamine overflow is increased in olfactory
bulbectomized rats: an in vivo microdialysis study. Physiol Behav 81: 111-119.
Mathews A, MacLeod C (2004) Cognitive Vulnerability to Emotional Disorders. Annu Rev Clin Psychol
1: 167-195.
Metzner R, Litwin G, Weil G M (1963) The Relation of Expectation and Mood to Psilocybin Reactions:
A Questionnaire Study. Psychedelic Rev 1:18-26.
Mittman S, Geyer M (1991) Dissociation of multiple effects of acute LSD on exploratory behavior in rats
by ritanserin and propranolol. Psychopharmacology 105: 69-76.
Montagne M (2007) Psychedelic therapy for the treatment of depression. In Winkelman M, Roberts TB
(eds), Psychedelic medicine: new evidence for hallucinogenic substances as treatments. Praeger
Publishers, Westport.
Nesterova I V, Gurevich E V, Nesterov V I, et al. (1997) Bulbectomy-induced loss of raphe neurons is
counteracted bt antidepressant treatment. Prog Neuropsychopharmacol Biol Psychiatry 21: 127-140.
Ogren S O (1986) Serotonin receptor involvement in the avoidance learning deficit caused by
pchloroamphetamine-induced serotonin release. Acta Physiol Scand 126: 449-462.
Osei-Owusu P, James A, Crane J, et al. (2005) 5-Hydroxytryptamine 1A Receptors in the Paraventricular
Nucleus of the Hypothalamus Mediate Oxytocin and Adrenocorticotropin Hormone Release and
Some Behavioral Components of the Serotonin Syndrome. J Pharmacol Exp Ther 313: 1324-1330.
Otmakhova N A, Gurevich E V, Katkov Y A, et al. (1992) Dissociation of multiple behavioral effects
between olfactory bulbectomized C57B1/6J and DBA/2J mice. Physiol Behav 52: 441-448.
Passie T (1997) Psycholytic and psychedelic therapy research 1931-1995: a complete international
bibliography. Laurentius, Hannover.
Ray T S (2010) Psychedelics and the human receptorome. PLoS ONE 5: e9019.
Riedlinger T J, Riedlinger J E (1994) Psychedelic and Entactogenic Drugs in the Treatment of
Depression. J Alt States Conscious 26: 41-55.
Romano A, Quinn J, Li L, et al. (2010) Intrahippocampal LSD accelerates learning and desensitizes the 5-
HT2A receptor in the rabbit. Psychopharmacology 212: 441-448.
Roth B L, Baner K, Westkaemper R, et al. (2002) Salvinorin A: A potent naturally occurring
nonnitrogenous κ opioid selective agonist. Proc Natl Acad Sci U S A 99: 11934-11939.
Sairanen M, Lucas G, Ernfors P, et al. (2005) Brain-Derived Neurotrophic Factor and Antidepressant
Drugs Have Different But Coordinated Effects on Neuronal Turnover, Proliferation, and Survival in
the Adult Dentate Gyrus. J Neurosci 25: 1089-1094.
Santarelli L, Saxe M, Gross C, et al. (2003) Requirement of Hippocampal Neurogenesis for the
Behavioral Effects of Antidepressants. Science 301: 805-809.
Savage C, Mc Cabe O L, Kurland A A, et al. (1973) LSD-assisted psychotherapy in the treatment of
severe chronic neuroses. J Alt States Conscious 1: 31-47.
Page 17 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Savitz J, Lucki I, Drevets W C (2009) 5-HT1A receptor function in major depressive disorder. Prog
Neurobiol 88: 17-31.
Schmidt J (1963) Die Beeinflussung einer bedingten motorischen Fluchtreaktion der Ratte durch
Noradrenalin, Serotonin und Lysergsäurediäthylamid. Acta Biol Med Ger 10: 343-349.
Song C, Leonard B E (2005) The olfactory bulbectomised rat as a model of depression. Neurosci
Biobehav Rev 29: 627-647.
Strassman R J (1984) Adverse Reactions to Psychedelic Drugs. A Review of the Literature. J Nerv Ment
Dis 172: 577-595.
Surget A, Tanti A, Leonardo E D, et al. (2011) Antidepressants recruit new neurons to improve stress
response regulation. Mol Psychiatry 16: 1177-1188.
Szabo S T, Blier P (2001) Effects of the selective norepinephrine reuptake inhibitor reboxetine on
norepinephrine and serotonin transmission in the rat hippocampus. Neuropsychopharmacology 25:
845-857.
Taeschler M, Weidmann H, Cerletti A (1960) The effect of LSD on reaction times in a conditioned
avoidance reaction and in the analgesia test. Helv Physiol Pharmacol Acta 18: 43-49.
Thomas J B (1973) Some behavioral effects of olfactory bulb damage in the rat. J Comp Physiol Psychol
83: 140-148.
Unger S M (1964) LSD and Psychotherapy: A Bibliography of the English-Language Literature. Psych
rev 1: 442-449.
Vaidya V A, Terwilliger R M Z, Duman R S (1999) Role of 5-HT2A receptors in the stress-induced
down-regulation of brain-derived neurotrophic factor expression in rat hippocampus. Neurosci Lett
262: 1-4.
Van der Stelt H M, Breuer M E, Olivier B, et al. (2005) Permanent deficits in serotonergic functioning of
olfactory bulbectomized rats: An in vivo microdialysis study. Biol Psychiatry 57: 1061-1067.
Vollenweider F X, Kometer M (2010) The neurobiology of psychedelic drugs: implications for the
treatment of mood disorders. Nat Rev Neurosci 11: 642-651.
Winkelman M J, Roberts T B (2007) Psychedelic Medicine: New Evidence for Hallucinogenic
Substances As Treatments. Praeger.
Zhang Y, Damjanoska K J, Carrasco G A, et al. (2002) Evidence That 5-HT2A Receptors in the
Hypothalamic Paraventricular Nucleus Mediate Neuroendocrine Responses to (−)DOI. J Neurosci
22: 9635-9642.
Page 18 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Figures and legends
Figure 1. Effect of bulbectomy and repeated LSD administration on conditioned (a) vs. instrumental (b)
pole-jumping learning over five consecutive days (mean +/- standard error of mean [SEM]): Repeated
measures ANOVA with pairwise contrast analysis revealed significant differences between sham/saline
and bulb/saline (F
[1, 14]
= 13.15, p = .003 [a]; F
[1, 14]
= 4.85, p = .045 [b]), bulb/saline and bulb/LSD (F
[4, 56]
= 2.6, p = .045 [a]), but not between sham/saline and bulb/LSD (F
[1, 16]
= 2.16, n. s. [a]; F
[1, 16]
= .813, n. s.
[b]). Sham = sham-operated rats, bulb = bulbectomised rats.
Page 19 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Figure 2. Effect of bulbectomy and repeated LSD treatment on specific ketanserin-sensitive
[
3
H]spiroperidol binding to frontocortical and hippocampal membranes. Note the trends of bulbectomy to
increase hippocampal 5-HT
2A
binding, and of LSD to counteract it. Mean + SEM (n = 4-6); comparison
of groups of interest, * p < .05, (NS) = trend (p < .10). Sham = sham-operated rats, bulb = bulbectomised
rats.
Page 20 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Figure 3. Effect of bulbectomy and repeated LSD application on [
35
S]-GTP-gamma-S binding to
hippocampal membranes stimulated by various agonists (per cent of basal binding). Note that from the
bulbectomy associated anomalies, LSD selectively normalised 5-HT
2
signalling (as induced by alpha-
MS). Mean + SEM (n = 4-6); comparison of groups of interest, * p < .05, (NS) = trend (p < .10). Sham =
sham-operated rats, bulb = bulbectomised rats; alpha-MS = alpha-methylserotonin.
Page 21 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Figure 4. Effect of bulbectomy and repeated LSD application on [
35
S]-GTP-gamma-S binding to
frontocortical membranes stimulated by various agonists (per cent of basal binding). Note that from the
bulbectomy associated anomalies, none was normalised by LSD. Mean + SEM (n = 4-6); comparison of
groups of interest, * p < .05, (NS) = trend (p < .10). Sham = sham-operated rats, bulb = bulbectomised
rats; alpha-MS = alpha-methylserotonin.
Page 22 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Effect of bulbectomy and repeated LSD administration on conditioned (a) vs. instrumental (b) pole-jumping
learning over five consecutive days (mean +/- standard error of mean [SEM]): Repeated measures ANOVA
with pairwise contrast analysis revealed significant differences between sham/saline and bulb/saline (F
[1, 14]
= 13.15, p = .003 [a]; F
[1, 14]
= 4.85, p = .045 [b]), bulb/saline and bulb/LSD (F
[4, 56]
= 2.6, p = .045 [a]),
but not between sham/saline and bulb/LSD (F
[1, 16]
= 2.16, n. s. [a]; F
[1, 16]
= .813, n. s. [b]). Sham =
sham-operated rats, bulb = bulbectomised rats.
112x51mm (300 x 300 DPI)
Page 23 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Effect of bulbectomy and repeated LSD treatment on specific ketanserin-sensitive [
3
H]spiroperidol binding to
frontocortical and hippocampal membranes. Note the trends of bulbectomy to increase hippocampal 5-HT
2A
binding, and of LSD to counteract it. Mean + SEM (n = 4-6); comparison of groups of interest, * p < .05,
(NS) = trend (p < .10). Sham = sham-operated rats, bulb = bulbectomised rats.
95x60mm (300 x 300 DPI)
Page 24 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Effect of bulbectomy and repeated LSD application on [
35
S]-GTP-gamma-S binding to hippocampal
membranes stimulated by various agonists (per cent of basal binding). Note that from the bulbectomy
associated anomalies, LSD selectively normalised 5-HT
2
signalling (as induced by alpha-
MS). Mean + SEM (n
= 4-6); comparison of groups of interest, * p < .05, (NS) = trend (p < .10). Sham = sham-operated rats,
bulb = bulbectomised rats; alpha-MS = alpha-methylserotonin.
115x75mm (300 x 300 DPI)
Page 25 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Effect of bulbectomy and repeated LSD application on [
35
S]-GTP-gamma-S binding to frontocortical
membranes stimulated by various agonists (per cent of basal binding). Note that from the bulbectomy
associated anomalies, none was normalised by LSD. Mean + SEM (n = 4-6); comparison of groups of
interest, * p < .05, (NS) = trend (p < .10). Sham = sham-operated rats, bulb = bulbectomised rats; alpha-
MS = alpha-methylserotonin.
113x72mm (300 x 300 DPI)
Page 26 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Peer Review
Repeated LSD in an animal model of depression
Original Paper
Repeated lysergic acid diethylamide (LSD) in an animal model of depression:
Normalisation of learning behaviour and hippocampal 5-HT
2
signalling
Tobias Buchborn
1,*
, Helmut Schröder
1
, Volker Höllt
1
, Gisela Grecksch
1
1
Institute of Pharmacology and Toxicology, Otto-von-Guericke University Magdeburg, 39120
Magdeburg, Germany
*Corresponding author: Dipl. Psych. Tobias Buchborn, Institute of Pharmacology and Toxicology,
Faculty of medicine, Otto-von-Guericke University Magdeburg, Leipziger Straße 44, 39120 Magdeburg,
Germany; phone: +49(0)391-67-21983, fax: +49(0)391-67-15869; e-mail: tobias.buchborn@med.ovgu.de
Disclaimer:
This research received no specific grant from any funding agency in the public,
commercial, or not-for-profit sectors.
The authors declare that there is no conflict of interest.
Page 27 of 26
http://mc.manuscriptcentral.com/jop
Journal of Psychopharmacology
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
