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Jiří Horáček

3rd Faculty of Medicine, Charles University, Ruská 87, Prague 10, 100 00, Czechia; Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czechia.

7 papers in the library · 68 citations · publishing 2013-2025

Papers

Behavioral, neurochemical and pharmaco-EEG profiles of the psychedelic drug 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in rats.

Psychopharmacology January 1, 2013 Tomáš Páleníček, Michaela Fujáková, Martin Brunovský et al. 51 citations

The synthetic compound 2C-B produces a biphasic effect on movement in rats: initial inhibition followed by excitation, while amphetamine only causes hyperactivity. Both drugs disrupt prepulse inhibition of the acoustic startle reaction, a measure of sensory gating, but have opposite effects on the startle itself. 2C-B increases dopamine and decreases its metabolite DOPAC in the nucleus accumbens, a brain region linked to reward. Low doses of 2C-B reduce electrical brain activity and connectivity; a high dose first decreases then increases brain wave power and connectivity. Increases in theta and alpha brain waves correlate with heightened movement and dopamine levels. These results suggest 2C-B shares properties with hallucinogens, entactogens, and stimulants, and its dopamine effects may indicate psychotomimetic and addictive potential.

Mescaline-induced behavioral alterations are mediated by 5-HT2A and 5-HT2C receptors in rats.

Pharmacology, biochemistry, and behavior December 1, 2024 Lucie Olejníková-Ladislavová, Michaela Fujáková-Lipski, Klára Šíchová et al. 5 citations

Mescaline, a classical psychedelic, primarily acts on serotonin 5-HT2A/C receptors but also binds to 5-HT1A and 5-HT2B receptors. In adult male rats, the highest dose (100 mg/kg) caused hyperlocomotion, which was reversed by almost all antagonists tested. Sensorimotor gating deficits, measured as prepulse inhibition of acoustic startle, were selectively normalized by a 5-HT2A antagonist, while a 5-HT2C antagonist partially reversed deficits from lower doses. These findings indicate that mescaline's behavioral effects are mainly mediated by the 5-HT2A receptor subtype, with a lesser role for 5-HT2C receptors, and limited involvement of other subtypes.

Cross-Species Evidence for Psilocin-Induced Visual Distortions: Apparent Motion Is Perceived by Both Humans and Rats.

Biological psychiatry global open science September 1, 2025 Čestmír Vejmola, Klára Šíchová, Kateřina Syrová et al. 4 citations

Psilocin, the active compound in psychedelic mushrooms, impairs the ability to distinguish between static and moving images in both humans and rats. In a visual discrimination task, human participants and male rats were asked to judge whether an image was static or moving. Under psilocin, both species showed significant difficulty in this task. In humans, the impairment tracked psilocin plasma levels and self-reported hallucination intensity. In rats, psilocin selectively disrupted performance in a motion-based task but not a luminance-based task, suggesting a specific effect on motion perception. Decision time was also linked to discrimination impairment. This is the first evidence that rats experience visual distortions similar to those reported by humans, offering a model for studying altered visual perception in drug-induced and psychiatric conditions.

The phenomenology of psilocybin's experience mediates subsequent persistent psychological effects independently of sex, previous experience, or setting.

Pharmacological reports : PR June 16, 2025 Tereza Klučková, Marek Nikolič, Filip Tylš et al. 4 citations

In healthy individuals, psilocybin produces lasting positive effects regardless of previous psychedelic experience, repeated use, setting, sex, or occupation. In a double-blind, placebo-controlled crossover study with 40 participants (20 females, mean age 38), each received two doses of psilocybin (0.26 mg/kg) at least 56 days apart. Acute effects were moderate on the Altered States of Consciousness Scales, with mostly pleasant or fluctuating experiences and only one unpleasant session; all sessions ended positively or neutrally. Long-term effects, assessed by the Persisting Effects Questionnaire, were positive across all domains with negligible negative effects. Peak experiences ending in a positive mood strongly predicted favorable long-term outcomes, while challenging experiences did not cause adverse outcomes. These findings support psilocybin's psychological safety and repeated use in clinical trials.

Acute pharmacological profile of 2C-B-Fly-NBOMe in male Wistar rats-pharmacokinetics, effects on behaviour and thermoregulation.

Frontiers in pharmacology January 1, 2023 Kateřina Syrová, Klára Šíchová, Hynek Danda et al. 4 citations

2C-B-Fly-NBOMe, a new psychoactive substance related to the psychedelic entactogen 2C-B, was studied in adult male Wistar rats. After injection, peak drug levels in blood serum occurred at 30 minutes (28 ng/ml) and in brain tissue at 60 minutes (171 ng/g), with the compound still detectable in the brain after 8 hours. The drug dose-dependently reduced locomotor activity and strongly disrupted the acoustic startle response, with a weaker effect on prepulse inhibition. It did not cause significant changes in body temperature. The overall profile resembles that of 2C-B and other NBOMe substances, suggesting slow brain penetration and inhibitory effects on motor performance and sensorimotor gating.

Behavioral pharmacology of mescaline - the role of serotonin 5-HT2A, 5-HT2B, 5-HT2C and 5-HT1A receptors

bioRxiv Preprint Server August 28, 2024 Lucie Olejníková-Ladislavová, Michaela Fujáková-Lipski, Klára Šíchová et al. preprint

Mescaline, a classical psychedelic with a phenylethylamine structure, primarily acts on serotonin 5-HT2A/C receptors but also binds to 5-HT1A and 5-HT2B receptors. Although it was the first psychedelic ever isolated and synthesized, the precise role of these different serotonin receptor subtypes in its behavioral pharmacology remains not fully understood.

DOES THE PHENOMENOLOGY OF THE PSILOCYBIN EXPERIENCE PREDICT LONG-TERM EFFECTS ON MOOD AND WELL-BEING IN HEALTHY VOLUNTEERS?

IBRO Neuroscience Reports November 6, 2023 Tomáš Páleníček, Tereza Kluckova, Marek Nikolic et al.

The study examined how the subjective experiences (phenomenology) induced by psilocybin, a psychedelic drug being tested as a rapid-acting antidepressant, relate to long-term changes in mood, spirituality, and relationships with self, life, and others. In healthy volunteers, positive aspects of the psychedelic experience were associated with beneficial long-term outcomes, while fearful aspects were linked to negative long-term outcomes. The findings suggest that the quality of the subjective experience during psilocybin use may influence its lasting psychological effects.