Role of the Serotonin 5-HT2A Receptor in LSD-induced Altered States of Consciousness (LDR-Study)

The present study explores the role the 5-HT2A receptor in LSD-induced altered states of consciousness using escalating doses of LSD and the 5-HT2A receptor blocker ketanserin administered before a high dose of LSD.

Topic Healthy Subjects
Compound Placebo LSD
Country Switzerland
Visit trial
Status Completed
Results Published Yes
Start date 28 November 2017
End date 11 July 2019
Chance of happening 100%
Phase Phase I
Design Blinded
Type Interventional
Generation First
Participants 16
Sex All
Age 25- 65
Therapy No

Trial Details

Serotonin receptors, especially the 5HT2A receptor, are thought to be involved in the effects of various recreationally used psychedelic substances such as LSD. LSD potently stimulates the 5-HT2A receptor but also 5-HT2B/C, 5-HT1 and dopaminergic receptors. LSD induces acute transient alterations in waking consciousness including visual perceptual alterations, audio-visual synesthesia, derealization and depersonalization. LSD has therefore been used as experimental tool ("psychotomimetic") in modern psychiatric research to study psychotic-like states and model psychosis in healthy subjects [1-5]. However, the dose-effects of 5-HT2A receptor stimulation by LSD has not yet been studied. Additionally, there is still very limited data to what extent the 5HT2A receptor contributes to LSD's effects and its role in the mediation of the full response to LSD at a high dose is unclear. A recent experimental human study showed the 5-HT2A receptor antagonist ketanserin fully blocked the subjective effects of a moderate dose of 100 µg of LSD [6]. But, whether the effects of a high 200 µg oral dose of LSD can be blocked by the selective pharmacological 5-HT2A antagonist ketanserin remains to be tested to confirm the critical role of the 5-HT2A receptor in more pronounced alterations of consciousness and perception. The present study therefore explores the role the 5-HT2A receptor in LSD-induced altered states of consciousness using escalating doses of LSD and the 5-HT2A receptor blocker ketanserin administered before a high dose of LSD.

NCT Number NCT03321136

Sponsors & Collaborators

University of Basel
The University of Basel Department of Biomedicine hosts the Liechti Lab research group, headed by Matthias Liechti.

Measures Used

5-Dimensional Altered States of Consciousness Questionnaire
The 5D-ASC scale measures altered states of consciousness and contains 94 items (visual analog scales).

Mystical Experience Questionnaire
The MEQ is a self-report measure that has been used to measure mystical-type experiences in laboratory studies of psychedelics. The scale was developed by Walter Pahnke in 1963 and covers the major dimensions of classic mystical experience: unity (internal and external), transcendence of time and space, noetic quality, sacredness, positive mood, and ineffability/paradoxicality. Variations of the MEQ exist; the MEQ-30 and the MEQ-43.

Data attribution

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