Sex-specific increased reactivity of the PVT and prolonged PVT→CeA circuit engagement following psilocin administration.

The psychedelic psilocybin has shown therapeutic potential, yet underlying neural mechanisms remain poorly understood. We investigated the impact of psilocin-the active metabolite of psilocybin-on basal activity and reactivity within the paraventricular nucleus of the thalamus (PVT) and PVT projections to central amygdala (CeA) in rats. Psilocin administration increased PVT c-Fos expression and selectively engaged PVT→CeA neurons in females, but not males. Psilocin enhanced PVT reactivity to an aversive air-puff stimulus, with effects primarily driven by passive responders. In PVT→CeA neurons, psilocin prevented time-dependent reductions in stimulus-evoked activity and maintained reactivity across timepoints in females but not males. The sustained engagement of PVT→CeA circuitry was driven by active responders. These findings identify sex-specific modulation of thalamic-limbic circuitry and behavior by psilocin, implicating PVT→CeA circuitry in the neural and behavioral effects of psychedelic compounds, advancing our understanding of how psychedelics modulate emotional brain circuits to further inform potential therapeutic mechanisms.