Psilocybin and its active metabolite psilocin have been shown to elicit rapid and long-lasting symptom improvements in a variety of affective psychiatric illnesses. However, the region-specific alterations underlying these therapeutic effects remain relatively unknown. The central amygdala (CeA) is a primary output region within the extended amygdala that is dysregulated in affective psychiatric disorders. Here, we measured CeA activity using the activity marker c-Fos and CeA reactivity using fiber photometry paired with an aversive air-puff stimulus. We found that psilocin administration acutely increased CeA activity in both males and females and increased stimulus specific CeA reactivity in females, but not males. In contrast, psilocin produced time-dependent decreases in reactivity in males, but not in females, as early as 2 days and lasting to 28 days post administration. We also measured behavioral responses to the air-puff stimulus and found sex-dependent changes in threat responding but not exploratory behavior or general locomotion. Repeated presentations of the auditory component of the air-puff were also performed and sex-specific effects of psilocin on CeA reactivity to the auditory-alone stimulus were also observed. This study provides new evidence that a single dose of psilocin produces sex-specific, time-dependent, and enduring changes in CeA reactivity and behavioral responding to specific components of an aversive stimulus.

Psilocybin, and its active metabolite psilocin, have been shown to elicit rapid and long-lasting symptom improvements in a variety of affective psychiatric illnesses. However, the specific mechanisms behind these therapeutic effects remain relatively unknown. The central amygdala (CeA) is a primary output region within the extended amygdala that is heavily dysregulated in affective psychiatric disorders. Here, we utilized fiber photometry to measure changes in CeA reactivity to an aversive air puff stimulus after psilocin administration, both acutely and at varying prolonged time points. We found that administration of psilocin increased reactivity acutely in females, but not males. Additionally, we show that one dose of psilocin produced decreases in reactivity in males, but not females, 28-days post administration, with decreases seen as early as 2-days post administration. We further report stimulus-specific changes in CeA reactivity after psilocin with differential responsivity to an aversive air puff stimulus and an auditory stimulus. We also measured changes in behavioral response to the air puff stimulus and report sex differences in threat responding but not exploratory behavior or general locomotion. This study provides evidence that a single dose of psilocin can elicit sex-specific, dynamic, and enduring changes in CeA reactivity to an aversive stimulus. These data are an important step towards dissecting circuit-based mechanisms underlying the effects of psychedelics.

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Alcohol use disorders are complex conditions characterized in part by excessive ethanol (EtOH) drinking and withdrawal-induced malaise. The corticotropin releasing factor-1 receptor (CRF1) has been implicated in EtOH drinking, affective states, and pain sensitivity; often in a sex-dependent manner. The studies presented here investigate the associations between baseline behavior, chronic intermittent EtOH intake, and withdrawal-induced affective behavior in male and female CRF1:cre:tdTomato rats. There were no sex differences in basal affective state or thermal sensitivity, as measured by the splash test, novelty suppressed feeding test, and Hargreaves, respectively. However, female rats displayed increased mechanical sensitivity, measured by the Von Frey test. Following baseline testing, rats underwent voluntary EtOH or water drinking under intermittent access conditions. Female rats consumed significantly more EtOH, but only during the first week. There were no group effects of EtOH on behavioral tests, but all of the rats demonstrated increased malaise upon repeated testing. There were significant individual differences where affective behavior positively correlated with negative affect in both sexes. There were also significant correlations between EtOH intake and CRF1-cFos co-expression in the infralimbic cortex and basolateral amygdala. EtOH decreased CRF1+ expression in the lateral amygdala, but there were no significant group effects of EtOH on cFos or CRF1-cFos co-expression in the medial prefrontal cortex or amygdala. Together, these results illustrate the complex interplay between affect, pain sensitivity, EtOH drinking, and the role of CRF1 containing neurons in mediating these behaviors.

In 2021, 131 million adult Americans reported drinking alcohol in the last month, despite the well-known consequences of alcohol consumption. While alcohol use disorders are associated with both mood and chronic pain disorders, the relationship between alcohol drinking and affective and nociceptive behaviors remains unclear. Corticotropin releasing factor receptor-1 (CRF1) has been implicated in alcohol drinking, affective states, and pain sensitivity; often in a sex-dependent manner. In order to probe the effects of alcohol drinking on activity of CRF1+ cells and to also test the hypothesis that alcohol drinking is associated with both basal and subsequent affective and nociceptive readouts, we put male and female CRF1:cre:tdTomato rats through a battery of behavioral tests before and after intermittent access to alcohol. Following baseline testing, rats began alcohol (or water) drinking. Females consumed more alcohol in the first week, but there was no effect of sex on overall alcohol intake. Following 3-4 weeks of drinking, behavioral tests were repeated. Alcohol drinking decreased mechanical sensitivity, but no other effects of alcohol drinking were observed between experimental groups. Individual alcohol intake correlated with affective behavior in both sexes but only correlated with thermal sensitivity in males. There were no main effects of alcohol drinking or sex on CRF1+ neuronal activity in the medial prefrontal cortex but final session alcohol intake correlated with activity in CRF1+ neurons in the infralimbic subregion. Together, our results suggest complex interplay between affective state, alcohol drinking, and the role of prefrontal CRF1+ neurons in mediating these behaviors.SIGNIFICANCE STATEMENTDespite alcohol use being extremely comorbid with mood and pain disorders, there is still a limited understanding of the interaction and directionality between the them. To investigate this problem, rats were tested for affective behavior before and after being allowed to drink alcohol for 6 weeks. While baseline behavior did not predict subsequent intake, alcohol intake predicted subsequent affective behavior on an individual subject basis. These findings were accompanied by increased activity of the corticotropin releasing factor 1 containing neurons in the infralimbic region of the prefrontal cortex. Together, these findings reveal a new mechanism for understanding alcohol use.