Ethopharmacological evaluation of antidepressant-like effect of serotonergic psychedelics in C57BL/6J male mice.

Serotonergic psychedelics like psilocin (the active metabolite of psilocybin), DOI, and TCB-2 produce antidepressant-like effects in mice by activating the 5-HT2A receptor. Twenty-four hours after a single injection, treated mice showed significantly less immobility in the forced swimming test and tail-suspension test—indicating reduced behavioral despair—compared to control mice. Blocking the 5-HT2A receptor with volinanserin eliminated these antidepressant-like effects. Psilocin's effect in the forced swimming test lasted at least three weeks. In the novelty-suppressed feeding test, psilocin reduced feeding latency (an anxiolytic-like effect), but volinanserin did not block this, and DOI and TCB-2 had no effect. None of the drugs altered spontaneous movement or head-twitch response. The findings suggest 5-HT2A activation mediates antidepressant but not anxiolytic effects of these psychedelics.

Study at a glance

Abstract

Serotonergic psychedelics such as psilocybin, lysergic acid diethylamide, and DOI exert a hallucinatory effect through serotonin 5-HT2A receptor (5-HT2A) activation. Recent studies have revealed that serotonergic psychedelics have therapeutic potential for neuropsychiatric disorders, including major depressive and anxiety-related disorders. However, the involvement of 5-HT2A in mediating the therapeutic effects of these drugs remains unclear. In this study, we ethopharmacologically analyzed the role of 5-HT2A in the occurrence of anxiolytic- and antidepressant-like effects of serotonergic psychedelics such as psilocin, an active metabolite of psilocybin, DOI, and TCB-2 in mice 24 h post-treatment. Mice with acute intraperitoneal psychedelic treatment exhibited significantly shorter immobility times in the forced swimming test (FST) and tail-suspension test (TST) than vehicle-treated control mice. These effects were eliminated by pretreatment with volinanserin, a 5-HT2A antagonist. Surprisingly, the decreasing immobility time in the FST in response to acute psilocin treatment was sustained for at least three weeks. In the novelty-suppressed feeding test (NSFT), the latency to feed, an indicator of anxiety-like behavior, was decreased by acute administration of psilocin; however, pretreatment with volinanserin did not diminish this effect. In contrast, DOI and TCB-2 did not affect the NSFT performance in mice. Furthermore, psilocin, DOI, and TCB-2 treatment did not affect the spontaneous locomotor activity or head-twitch response, a hallucination-like behavior in rodents. These results suggest that 5-HT2A contributes to the antidepressant effects of serotonergic psychedelics rather than anxiolytic effects.