Acute Effects of Hallucinogens on Functional Connectivity: Psilocybin and Salvinorin-A

Using fMRI in nonhuman primates, this work compared how two different hallucinogens—psilocybin, a serotonergic psychedelic, and salvinorin-A, a kappa-opioid receptor agonist—alter resting-state functional connectivity. Both drugs acutely desynchronized the default mode network and affected a network involving the claustrum, prefrontal cortex, anterior cingulate cortices, and angular gyrus, supporting a cortico-claustro-cortical model for probing hallucinogen effects regardless of serotonergic activity. Thalamo-cortical changes appeared dependent on 5-HT2AR activation. The findings offer a framework for understanding mechanisms common across hallucinogenic drug classes.

Study at a glance

Abstract

The extent of changes in functional connectivity (FC) within functional networks as a common feature across hallucinogenic drug classes is under-explored. This work utilized fMRI to assess the dissociative hallucinogens Psilocybin, a classical serotonergic psychedelic, and Salvinorin-A, a kappa-opioid receptor (KOR) agonist, on resting-state FC in nonhuman primates. We highlight overlapping and differing influence of these substances on FC relative to the thalamus, claustrum, prefrontal cortex (PFC), default mode network (DMN), and DMN subcomponents. Analysis was conducted on a within-subject basis. Findings support the cortico-claustro-cortical network model for probing functional effects of hallucinogens regardless of serotonergic potential, with a potential key paradigm centered around the claustrum, PFC, anterior cingulate cortices (ACC), and angular gyrus relationship. Thalamo-cortical networks are implicated but appear dependent on 5-HT2AR activation. Acute desynchronization relative to the DMN for both drugs was also shown. Our findings provide a framework to understand broader mechanisms at which hallucinogens in differing classes may impact subjects regardless of the target receptor.