Journal of Pain
August 1, 2026
Jon G. Dean, Ethan Hurwitz, T. Furnish et al.
Phantom limb pain (PLP) is a refractory condition defined by pain experienced in a missing limb. Psilocybin, a classical serotonergic psychedelic drug, can alleviate various treatment-resistant disorders but has scantly been investigated for chronic pain. This placebo-controlled, double-blind, randomized clinical pilot trial (NCT05224336) tested the feasibility, tolerability, and preliminary...
Cognitive Therapy and Research
March 29, 2025
Federico Seragnoli, Fabienne Picard, Gabriel Thorens et al.
4 citations
Abstract Purpose Despite the presence of mystical-type experiences in psychedelic-assisted therapy (PAT), an understanding of the cognitive processes involved is still lacking. Guided by theory and empirical research, we hypothesized a cognitive-grounded perspective based on current metacognition models to promote the understanding of the psychological processes involved in mystical-type...
Biological psychiatry. Cognitive neuroscience and neuroimaging
May 1, 2024
Mark A. Geyer
30 citations
Classical serotonergic psychedelics such as lysergic acid diethylamide or the naturally occurring compounds psilocybin and mescaline produce profound changes in mood, thought, intuition, sensory perception, the experience of time and space, and even the experience of self. Research examining psychedelic compounds has had a complex and turbulent evolution. Many cultures throughout the world have...
Psychedelic Med (New Rochelle)
March 13, 2023
Peter S. Hendricks, Charles D. Nichols, Kathryn A. Cunningham et al.
7 citations
Past, Present, and Future of Psychedelics: A Psychedelic Medicine Roundtable Discussion.
The International Journal of Neuropsychopharmacology
November 12, 2021
Benjamin Z Roberts, Arpi Minassian, Adam L. Halberstadt et al.
HIV-associated neurocognitive disorder (HAND) is commonly observed in persons living with HIV (PWH) and is characterized by cognitive deficits implicating disruptions of fronto-striatal neurocircuitry. Such circuitry is also susceptible to alteration by cannabis and other drugs of abuse. PWH use cannabis at much higher rates than the general population, thus prioritizing the characterization of...
Psychopharmacology
February 14, 2019
Adam L. Halberstadt, Jochem V. F. Zee, Muhammad Chatha et al.
21 citations
Background There is evidence that mGlu2/3 receptors regulate 5-HT_2A signaling, interactions that have been theorized to play a role in the antipsychotic-like effects of mGlu2/3 agonists as well as the hallucinogenic effects of 5-HT_2A agonists. One approach to unraveling this interaction is through the chronic administration of agonists at the two receptors, which should influence the...
Current Topics in Behavioral Neurosciences
2016
Mark A. Geyer, Adam L. Halberstadt
104 citations
Because of the ethical and regulatory hurdles associated with human studies, much of what is known about the psychopharmacology of hallucinogens has been derived from animal models. However, developing reliable animal models has proven to be a challenging task due to the complexity and variability of hallucinogen effects in humans. This chapter focuses on three animal models that are frequently...
Neuropharmacology
February 1, 2014
Adam L. Halberstadt, Mark A. Geyer
113 citations
N-benzyl substitution markedly enhances the affinity of phenethylamine hallucinogens at the 5-HT(2A) receptor. N-benzyl substituted derivatives of 2,5-dimethoxy-4-iodophenethylamine (2C-I), such as N-(2-methoxybenzyl)-2,5-dimethoxy-4-iodophenethylamine (25I-NBOMe) and N-(2,3-methylenedioxybenzyl)-2,5-dimethoxy-4-iodophenethylamine (25I-NBMD), have appeared recently as designer drugs, but have...
The International Journal of Neuropsychopharmacology
August 13, 2013
Adam L. Halberstadt, Mark A. Geyer
66 citations
Abstract One of the oldest models of schizophrenia is based on the effects of serotonergic hallucinogens such as mescaline, psilocybin, and (+)-lysergic acid diethylamide (LSD), which act through the serotonin 5-HT2A receptor. These compounds produce a ‘model psychosis’ in normal individuals that resembles at least some of the positive symptoms of schizophrenia. Based on these similarities, and...
Psychopharmacology
June 1, 2012
Adam L. Halberstadt, David E Nichols, Mark A. Geyer
55 citations
Ayahuasca is a psychoactive tea prepared from a combination of plants that contain a hallucinogenic tryptamine and monoamine oxidase inhibitors (MAOIs). Behavioral pattern monitor (BPM) experiments demonstrated that the combination of 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) and a behaviorally inactive dose of an MAO(A) inhibitor such as harmaline or clorgyline induces biphasic effects on...
Neuropsychopharmacology
September 28, 2011
Boris B. Quednow, Michael Kometer, Mark A. Geyer et al.
241 citations
The serotonin-2A receptor (5-HT(2A)R) has been implicated in the pathogenesis of schizophrenia and related inhibitory gating and behavioral inhibition deficits of schizophrenia patients. The hallucinogen psilocybin disrupts automatic forms of sensorimotor gating and response inhibition in humans, but it is unclear so far whether the 5-HT(2A)R or 5-HT(1A)R agonist properties of its bioactive...
Psychopharmacology
December 9, 2010
Adam L. Halberstadt, Virginia Lehmann-Masten, Mark A. Geyer et al.
35 citations
RATIONALE: Metabotropic glutamate (mGlu) receptors have been suggested to play a role in neuropsychiatric disorders including schizophrenia, drug abuse, and depression. Because serotonergic hallucinogens increase glutamate release and mGlu receptors modulate the response to serotonin (5-HT)(2A) activation, the interactions between serotonin 5-HT(2A) receptors and mGlu receptors may prove to be...
Journal of Psychopharmacology
December 8, 2010
Liselore Koedood, Adam L. Halberstadt, Susan B Powell et al.
212 citations
Psilocin (4-hydroxy- N, N-dimethyltryptamine) is a hallucinogen that acts as an agonist at 5-HT 1A , 5-HT 2A , and 5-HT 2C receptors. Psilocin is the active metabolite of psilocybin, a hallucinogen that is currently being investigated clinically as a potential therapeutic agent. In the present investigation, we used a combination of genetic and pharmacological approaches to identify the...
Psychopharmacology
November 24, 2009
Adam L. Halberstadt, Mark A. Geyer
76 citations
RATIONALE: Compounds that activate the 5-HT(2A) receptor, such as lysergic acid diethylamide (LSD), act as hallucinogens in humans. One notable exception is the LSD congener lisuride, which does not have hallucinogenic effects in humans even though it is a potent 5-HT(2A) agonist. LSD and other hallucinogens have been shown to disrupt prepulse inhibition (PPI), an operational measure of...
Pharmacology, biochemistry, and behavior
September 1, 2009
Vikas Duvvuri, Victoria B Risbrough, Walter H. Kaye et al.
7 citations
We propose a translational approach to the study of anorexia nervosa (AN) based on our human subject studies where there are characteristic elevations in 5-HT(1A) receptor binding, associated harm avoidance behaviors, reduced impulsivity, and comorbid anxiety disorders. Towards this goal, the hyponeophagia assay was implemented whereby food-deprived mice show increased latency to begin feeding...
Neuropsychopharmacology
July 1, 2009
Adam L. Halberstadt, Iris Van der Heijden, Michael A Ruderman et al.
Although it is well established that hallucinogens act as 5-HT_2A and 5-HT_2C receptor agonists, little is known about the relative contributions of 5-HT_2A and 5-HT_2C receptors to the acute behavioral effects of these drugs. The behavioral pattern monitor was used to characterize the effects of the hallucinogen 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) on locomotor and investigatory...
Journal of young investigators
July 1, 2009
Michael A Ruderman, S. Powell, M. Geyer
Sensorimortor gating and locomotion are behaviors that reflect pre-attentive sensory filtering and higher order, top-down, sensory processing, respectively. These processes are thought to affect either the perception of novelty in an environment (filtering) or cognition (higher order processing), salient features of models of altered states of consciousness (ASC). Drugs with highly selective...
Psychopharmacology
November 1, 2008
Adam L. Halberstadt, Mahalah R Buell, Virginia L Masten et al.
46 citations
The hallucinogenic tea known as ayahuasca is made from a combination of psychoactive plants that contribute the active components N,N-dimethyltryptamine (DMT) and 5-methoxy-DMT (5-MeO-DMT), as well as the monoamine oxidase (MAO) inhibitors (MAOIs) harmine and harmaline for oral activity. The present study examined the effects of 5-MeO-DMT in combination with MAOIs in rats using the behavioral...
Trends in Pharmacological Sciences
August 1, 2008
Mark A. Geyer, Franz X. Vollenweider
435 citations
The history of serotonin research is closely related to the study of hallucinogenic drugs that function as agonists at serotonin-2A receptors. The fundamental idea that psychotic states seen in psychiatric disorders such as schizophrenia might be attributable, in part, to abnormalities in serotonergic systems began with the almost simultaneous discovery of lysergic acid diethylamide (LSD),...
Journal of Psychopharmacology
May 1, 2007
Karsten Heekeren, Anna Neukirch, Jörg Daumann et al.
49 citations
Patients with schizophrenia exhibit diminished prepuLse inhibition (PPI) of the acoustic startle reflex and deficits in the attentional moduLation of PPI. Pharmacological challenges with hallucinogens are used as models for psychosis in both humans and animals. RemarkabLy, in contrast to the findings in schizophrenic patients and in animal hallucinogen modeLs of psychosis, previous studies with...
Neuropsychopharmacology
February 14, 2007
Franz X. Vollenweider, Philipp Csomor, Bernhard Knappe et al.
194 citations
Schizophrenia patients exhibit impairments in prepulse inhibition (PPI) of the startle response. Hallucinogenic 5-HT(2A) 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-HT(2A) receptor agonist psilocybin increases PPI in healthy humans....
Psychopharmacology
December 1, 2006
Kirsten Krebs-Thomson, Erbert M Ruiz, Virginia L Masten et al.
96 citations
The hallucinogen 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT) is structurally similar to other indoleamine hallucinogens such as LSD. The present study examined the effects of 5-MeO-DMT in rats using the Behavioral Pattern Monitor (BPM), which enables analyses of patterns of locomotor activity and exploration, and the prepulse inhibition of startle (PPI) paradigm. A series of interaction...
Psychopharmacology
May 2004
Karsten Heekeren, Jörg Daumann, Mark A Geyer et al.
3,4-Methylenedioxymethamphetamine (MDMA, ecstasy) is neurotoxic upon central serotonin systems in experimental animals and probably also in humans. Serotonin is involved in the habituation, sensitization and prepulse inhibition (PPI) of the startle reflex. To study the plasticity of startle reflex in currently abstinent MDMA users. Electromyographic responses to acoustic startle stimuli (pulse...
Journal of Psychoactive Drugs
June 1, 2002
Franz X. Vollenweider, Matthias E. Liechti, Alex Gamma et al.
92 citations
Since the mid 1990s, MDMA has been increasingly used as a recreational drug called "Ecstasy" by young people in Europe and the United States. However, despite the widespread recreational use of Ecstasy, systematic data on the psychological and neurobiological effects of MDMA have been scant. To further our understanding of the mechanism of action of MDMA, the authors conducted several studies...
Addiction Research & Theory
2002
Diana L. Martinez-Price, Kirsten Krebs-Thomson, Mark A. Geyer
16 citations
Since being classified as a Schedule I controlled substance, MDMA (3,4-methylenedioxy-N-methylamphetamine; "ecstasy") has been the subject of controversy regarding its potential therapeutic usage, increased use by young people in the "Rave" culture, and issues of potential neurotoxicity. This review article summarizes much of the animal and human studies of the general behavioral effects of...