OPEN Foundation

Menu
Search
Close this search box.

Psychiatry

Psilocybin links binocular rivalry switch rate to attention and subjective arousal levels in humans

September 14, 2007 / Mushrooms / Psilocybin, Neuroscience, Other subjects, Papers, Psychiatry, Psychopharmacology, Publications / By / , , , , ,

Abstract

Rationale: Binocular rivalry occurs when different images are simultaneously presented to each eye. During continual viewing of this stimulus, the observer will experience repeated switches between visual awareness of the two images. Previous studies have suggested that a slow rate of perceptual switching may be associated with clinical and drug-induced psychosis.

Objectives: The objective of the study was to explore the proposed relationship between binocular rivalry switch rate and subjective changes in psychological state associated with 5-HT2A receptor activation.

Materials and methods: This study used psilocybin, the hallucinogen found naturally in Psilocybe mushrooms that had previously been found to induce psychosis-like symptoms via the 5-HT2A receptor. The effects of psilocybin (215 μg/kg) were considered alone and after pretreatment with the selective 5-HT2A antagonist ketanserin (50 mg) in ten healthy human subjects.

Results: Psilocybin significantly reduced the rate of binocular rivalry switching and increased the proportion of transitional/mixed percept experience. Pretreatment with ketanserin blocked the majority of psilocybin’s “positive” psychosis-like hallucinogenic symptoms. However, ketanserin had no influence on either the psilocybin-induced slowing of binocular rivalry or the drug’s “negative-type symptoms” associated with reduced arousal and vigilance.

Conclusions: Together, these findings link changes in binocular rivalry switching rate to subjective levels of arousal and attention. In addition, it suggests that psilocybin’s effect on binocular rivalry is unlikely to be mediated by the 5-HT2A receptor.

Carter, O. L., Hasler, F., Pettigrew, J. D., Wallis, G. M., Liu, G. B., & Vollenweider, F. X. (2007). Psilocybin links binocular rivalry switch rate to attention and subjective arousal levels in humans. Psychopharmacology, 195(3), 415-424. 10.1007/s00213-007-0930-9

Link to full text

Effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in Santo Daime members

July 27, 2007 / Anxiety disorders / PTSD, Ayahuasca, Depression, Papers, Psychiatry, Psychology, Psychopharmacology, Publications, Safety / By / , , , ,

Abstract

The use of the hallucinogenic brew ayahuasca, obtained from infusing the shredded stalk of the malpighiaceous plant Banisteriopsis caapi with the leaves of other plants such as Psychotria viridis, is growing in urban centers of Europe, South and North America in the last several decades. Despite this diffusion, little is known about its effects on emotional states. The present study investigated the effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in members of the Santo Daime, an ayahuasca-using religion. Standard questionnaires were used to evaluate state-anxiety (STAI-state), trait-anxiety (STAI-trait), panic-like (ASI-R) and hopelessness (BHS) in participants that ingested ayahuasca for at least 10 consecutive years. The study was done in the Santo Daime church, where the questionnaires were administered 1 h after the ingestion of the brew, in a double-blind, placebo-controlled procedure. While under the acute effects of ayahuasca, participants scored lower on the scales for panic and hopelessness related states. Ayahuasca ingestion did not modify state- or trait-anxiety. The results are discussed in terms of the possible use of ayahuasca in alleviating signs of hopelessness and panic-like related symptoms.

Santos, R. G., Landeira-Fernandez, J., Strassman, R. J., Motta, V., & Cruz, A. P. M. (2007). Effects of ayahuasca on psychometric measures of anxiety, panic-like and hopelessness in Santo Daime members. Journal of Ethnopharmacology, 112(3), 507-513. http://dx.doi.org/10.1016/j.jep.2007.04.012
Link to full text

The effects of the preferential 5-HT2A agonist psilocybin on prepulse inhibition of startle in healthy human volunteers depend on interstimulus interval

February 14, 2007 / Mushrooms / Psilocybin, Neuroscience, Papers, Psychiatry, Psychology, Psychosis, Publications / By / , , , ,

Abstract

Schizophrenia patients exhibit impairments in prepulse inhibition (PPI) of the startle response. Hallucinogenic 5-HT2A receptor agonists are used for animal models of schizophrenia because they mimic some symptoms of schizophrenia in humans and induce PPI deficits in animals. Nevertheless, one report indicates that the 5-HT2A receptor agonist psilocybin increases PPI in healthy humans. Hence, we investigated these inconsistent results by assessing the dose-dependent effects of psilocybin on PPI in healthy humans. Sixteen subjects each received placebo or 115, 215, and 315 mug/kg of psilocybin at 4-week intervals in a randomized and counterbalanced order. PPI at 30-, 60-, 120-, 240-, and 2000-ms interstimulus intervals (ISIs) was measured 90 and 165 min after drug intake, coinciding with the peak and post-peak effects of psilocybin. The effects of psilocybin on psychopathological core dimensions and sustained attention were assessed by the Altered States of Consciousness Rating Scale (5D-ASC) and the Frankfurt Attention Inventory (FAIR). Psilocybin dose-dependently reduced PPI at short (30 ms), had no effect at medium (60 ms), and increased PPI at long (120–2000 ms) ISIs, without affecting startle reactivity or habituation. Psilocybin dose-dependently impaired sustained attention and increased all 5D-ASC scores with exception of Auditory Alterations. Moreover, psilocybin-induced impairments in sustained attention performance were positively correlated with reduced PPI at the 30 ms ISI and not with the concomitant increases in PPI observed at long ISIs. These results confirm the psilocybin-induced increase in PPI at long ISIs and reveal that psilocybin also produces a decrease in PPI at short ISIs that is correlated with impaired attention and consistent with deficient PPI in schizophrenia.

Vollenweider, F. X, Csomor, P. A., Knappe, B., Geyer, M. A., & Quednow, B. B. (2007). The effects of the preferential 5-HT2A agonist psilocybin on prepulse inhibition of startle in healthy human volunteers depend on interstimulus interval. Neuropsychopharmacology, 32(9), 1876-1887. http://dx.doi.org/10.1038/sj.npp.1301324
Link to full text

Hallucinogens recruit specific cortical 5-HT(2A) receptor-mediated signaling pathways to affect behavior.

February 1, 2007 / LSD, Mushrooms / Psilocybin, Neuroscience, Papers, Psychiatry, Psychology, Psychopharmacology, Publications / By / , , , , , ,

Abstract

Hallucinogens, including mescaline, psilocybin, and lysergic acid diethylamide (LSD), profoundly affect perception, cognition, and mood. All known drugs of this class are 5-HT(2A) receptor (2AR) agonists, yet closely related 2AR agonists such as lisuride lack comparable psychoactive properties. Why only certain 2AR agonists are hallucinogens and which neural circuits mediate their effects are poorly understood. By genetically expressing 2AR only in cortex, we show that 2AR-regulated pathways on cortical neurons are sufficient to mediate the signaling pattern and behavioral response to hallucinogens. Hallucinogenic and nonhallucinogenic 2AR agonists both regulate signaling in the same 2AR-expressing cortical neurons. However, the signaling and behavioral responses to the hallucinogens are distinct. While lisuride and LSD both act at 2AR expressed by cortex neurons to regulate phospholipase C, LSD responses also involve pertussis toxin-sensitive heterotrimeric G(i/o) proteins and Src. These studies identify the long-elusive neural and signaling mechanisms responsible for the unique effects of hallucinogens.

González-Maeso, J., Weisstaub, N. V., Zhou, M., Chan, P., Ivic, L., Ang, R., … & Gingrich, J. A. (2007). Hallucinogens recruit specific cortical 5-HT 2A receptor-mediated signaling pathways to affect behavior. Neuron, 53(3), 439-452.  http://dx.doi.org/10.1016/j.neuron.2007.01.008

Link to full text

Safety, tolerability, and efficacy of psilocybin in 9 patients with obsessive-compulsive disorder

November 11, 2006 / Anxiety disorders / PTSD, Mushrooms / Psilocybin, Other subjects, Papers, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications, Safety / By / , , ,

Abstract

Background: Anecdotal reports suggest that psychedelic agents may relieve symptoms of obsessive-compulsive disorder (OCD). This modified double-blind study investigated the safety, tolerability, and clinical effects of psilocybin, a potent 5-HT(1A) and 5-HT(2A/2C) agonist, in patients with OCD.

Method: Nine subjects with DSM-IV-defined OCD and no other current major psychiatric disorder participated in up to 4 single-dose exposures to psilocybin in doses ranging from sub-hallucinogenic to frankly hallucinogenic. Low (100 microg/kg), medium (200 microg/kg), and high (300 microg/kg) doses were assigned in that order, and a very low dose (25 microg/kg) was inserted randomly and in double-blind fashion at any time after the first dose. Testing days were separated by at least 1 week. Each session was conducted over an 8-hour period in a controlled environment in an outpatient clinic; subjects were then transferred to a psychiatric inpatient unit for overnight observation. The Yale-Brown Obsessive Compulsive Scale (YBOCS) and a visual analog scale measuring overall obsessive-compulsive symptom severity were administered at 0, 4, 8, and 24 hours post-ingestion. The Hallucinogen Rating Scale was administered at 8 hours, and vital signs were recorded at 0, 1, 4, 8, and 24 hours after ingestion. The study was conducted from November 2001 to November 2004.

Results: Nine subjects were administered a total of 29 psilocybin doses. One subject experienced transient hypertension without relation to anxiety or somatic symptoms, but no other significant adverse effects were observed. Marked decreases in OCD symptoms of variable degrees were observed in all subjects during 1 or more of the testing sessions (23%-100% decrease in YBOCS score). Repeated-measures analysis of variance for all YBOCS values revealed a significant main effect of time on Wilks lambda (F = 9.86, df = 3,3; p = .046), but no significant effect of dose (F = 2.25, df = 3,3; p = .261) or interaction of time and dose (F = 0.923, df = 9,45; p = .515). Improvement generally lasted past the 24-hour timepoint.

Conclusion: In a controlled clinical environment, psilocybin was safely used in subjects with OCD and was associated with acute reductions in core OCD symptoms in several subjects.
Moreno, F. A., Wiegand, C. B., Taitano, E. K., & Delgado, P. L. (2006). Safety, tolerability, and efficacy of psilocybin in 9 patients with obsessive-compulsive disorder. Journal of Clinical Psychiatry, 67(11), 1735-1740.

Link to full text

Effects of mescaline and lysergic acid (d-LSD-25)

April 6, 2006 / Anxiety disorders / PTSD, Cacti / Mescaline, LSD, Papers, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications / By / , ,

Abstract

The effects of mescaline and lysergic acid were studied in schizophrenic patients. It was found that physiological changes were produced in these patients and that their mental symptomatology was markedly aggravated. The observations made with the above-mentioned drugs on normal individuals were compared with those seen in schizophrenic patients. Mescaline and lysergic acid are drugs that disorganize the psychic integration of a person. This disorganization is much more apparent in schizophrenics than in normals. The diagnostic, prognostic, and therapeutic use of these drugs is also discussed.

Hoch, P. H., Cattell, J. P., & Pennes, H. H. (1952). Effects of mescaline and lysergic acid (d-LSD-25). American Journal of Psychiatry, 108(8), 579-584.,10.1176/ajp.108.8.579

Link to full text

Acute dose of MDMA (75 mg) impairs spatial memory for location but leaves contextual processing of visuospatial information unaffected

March 1, 2006 / MDMA, Other subjects, Papers, Psychiatry, Psychology, Publications / By / ,

Abstract

Rationale: Research concerning spatial memory in 3,4-methylenedioxymethamphetamine (MDMA) users has presented conflicting results showing either the presence or absence of spatial memory deficits. Two factors may have confounded results in abstinent users: memory task characteristics and polydrug use.

Objectives: The present study aims to assess whether a single dose of MDMA affects spatial memory performance during intoxication and withdrawal phase and whether spatial memory performance after MDMA is task dependent.

Materials and methods: Eighteen recreational MDMA users participated in a double-blind, placebo-controlled, three-way crossover design. They were treated with placebo, MDMA 75 mg, and methylphenidate 20 mg. Memory tests were conducted between 1.5 and 2 h (intoxication phase) and between 25.5 and 26 h (withdrawal phase) post-dosing. Two spatial memory tasks of varying complexity were used that required either storage of stimulus location alone (spatial memory task) or memory for location as well as processing of content or contextual information (change blindness task).

Results: After a single dose of MDMA, the subjects made larger localization errors and responded faster compared to placebo in the simple spatial memory task during intoxication phase. Inaccuracy was not due to increased response speed, as determined by regression analysis. Performance in the change blindness task was not affected by MDMA. Methylphenidate did not affect performance on any of the tasks.

Conclusion: It is concluded that a single dose of MDMA impairs spatial memory for location but leaves processing of contextual information intact.

Kuypers, K. P., & Ramaekers, J. G. (2007). Acute dose of MDMA (75 mg) impairs spatial memory for location but leaves contextual processing of visuospatial information unaffected. Psychopharmacology, 189(4), 557-563. 10.1007/s00213-006-0321-7

Link to full text

Mechanisms of antiaddictive actions of ibogaine

February 7, 2006 / Iboga / Ibogaine, Papers, Psychiatry, Psychology, Psychopharmacology, Publications, Substance Use Disorder / By / ,

Abstract

Ibogaine, an alkaloid extracted from Tabemanthe iboga, is being studied as a potential long-acting treatment for oploid and stimulant abuse as well as for alcoholism and smoking. Studies in this laboratory have used animal models to characterize ibogaine’s interactions with drugs of abuse, and to investigate the mechanisms responsible. Ibogaine, as well as its metabolite, noribogaine, can decrease both morphine and cocaine self-administration for several days in some rats; shorter-lasting effects appear to occur on ethanol and nicotine intake. Acutely, both ibogaine and noribogaine decrease extracellular levels of dopamine in the nucleus accumbens of rat brain. Ibogaine pretreatment (19 hours beforehand) blocks morphine-induced dopamine release and morphine-induced locomotor hyperactivity while, in contrast, it enhances similar effects of stimulants (cocaine and amphetamine). Ibogaine pretreatment also blocks nicotine-induced dopamine release. Both ibogaine and noribogaine bind to kappa opioid and N-methyl-D-aspartate (NMDA) receptors and to serotonin uptake sites; ibogaine also binds to sigma-2 and nicotinic receptors. The relative contributions of these actions are being assessed. Our ongoing studies in rats suggest that kappa agonist and NMDA antagonist actions contribute to ibogaine’s effects on opioid and stimulant self-administration, while the serotonergic actions may be more important for ibogaine-induced decreases in alcohol intake. A nicotinic antagonist action may mediate ibogaine-induced reduction of nicotine preferences in rats. A sigma-2 action of ibogaine appears to mediate its neurotoxicity. Some effects of ibogaine (e.g., on morphine and cocaine self-administration, morphine-induced hyperactivity, cocaine-induced increases in nucleus accumbens dopamine) are mimicked by kappa agonist (U50,488) and/or a NMDA antagonist (MK-801). Moreover, a combination of a kappa antagonist and a NMDA agonist will partially reverse several of ibogaine’s effects. Ibogaine’s long-term effects may be mediated by slow release from fat tissue (where ibogaine is sequestered) and conversion to noribogaine. Different receptors, or combinations of receptors, may mediate interactions of ibogaine with different drugs of abuse.

Glick, S. D., & Maisonneuve, I. S. (1998). Mechanisms of antiaddictive actions of ibogaine. Annals of the New York Academy of Sciences, 844, 214-226. http://dx.doi.org/10.1111/j.1749-6632.1998.tb08237.x
Link to full text

Screening the receptorome for plant-based psychoactive compounds

December 22, 2005 / Ayahuasca, Neuroscience, Other subjects, Papers, Psychiatry, Psychology, Psychopharmacology, Publications, Salvia / Salvinorin A / By / ,

Abstract

Throughout time, humans have used psychoactive plants and plant-derived products for spiritual, therapeutic and recreational purposes. Furthermore, the investigation of psychoactive plants such as Cannabis sativa (marijuana), Nicotiana tabacum (tobacco) and analogues of psychoactive plant derivatives such as lysergic acid diethylamide (LSD) have provided insight into our understanding of neurochemical processes and diseases of the CNS. Currently, many of these compounds are being used to treat a variety of diseases, such as depression and anxiety in the case of Piper methysticum Kava Kava (Martin et al., 2002; Singh and Singh, 2002). G-protein coupled receptors (GPCRs) are the most common molecular target for both psychoactive drugs and pharmaceuticals. The “receptorome” (that portion of the genome encoding ligand reception) encompasses more than 8% of the human genome (Roth et al., 2004) and as such provides a large number of possible targets for psychoactive drug interactions. A systematic, comprehensive study is necessary to identify novel active psychoactive plant-based compounds and the molecular targets of known compounds. Herein we describe the development of a high throughput system (HTS) to screen psychoactive compounds against the receptorome and present two examples (Salvia divinorum, the “magic mint” hallucinogen and Banisteriopsis caapi, the main component of Ayahuasca, a psychoactive beverage) where HTS enabled the identification of the molecular target of each compound.

O’connor, K. A., & Roth, B. L. (2005). Screening the receptorome for plant-based psychoactive compounds. Life sciences, 78(5), 506-511. 10.1016/j.lfs.2005.09.002
Link to full text

Transient memory impairment after acute dose of 75mg 3.4-Methylene-dioxymethamphetamine

November 1, 2005 / MDMA, Other subjects, Papers, Psychiatry, Psychology, Publications / By / ,

Abstract

A range of studies has indicated that users of 3.4-Methylene-dioxymethamphetamine (MDMA, ‘Ecstasy’) display cognitive deficits, particularly memory impairment, as compared to non-drug using controls. Yet it is difficult to determine whether these deficits are caused by MDMA or some other confounding factor, such as polydrug use. The present study was designed to establish the direct relation between MDMA and memory impairment under placebo-controlled conditions. Eighteen recreational MDMA users participated in a double blind, placebo controlled, 3-way crossover design. They were treated with placebo, MDMA 75mg and methylphenidate 20mg. Memory tests were conducted between 1.5-2h (intoxication phase) and between 25.5-26h (withdrawal phase) post dosing. Results showed that a single dose of MDMA caused impairment of immediate and delayed recall on a verbal learning task during the intoxication phase. However, there was no residual memory impairment during the withdrawal phase. Subjects reported more fatigue and less vigour, but no symptoms of depression during the withdrawal phase of MDMA treatment.

Methylphenidate did not affect memory or mood at any time of testing. A single dose of MDMA produces transient memory impairment.

Kuypers, K. P., & Ramaekers, J. G. (2005). Transient memory impairment after acute dose of 75mg 3.4-Methylene-dioxymethamphetamine. Journal of Psychopharmacology, 19(6), 633-639. 10.1177/0269881105056670
Link to full text