CB1R blockade unmasks TRPV1-mediated contextual fear generalization in female, but not male rats

Abstract

Increasing evidence suggests that the neurobiological processes that govern learning and memory can be different in males and females, but many of the specific mechanisms underlying these sex differences have not been fully defined. Here we investigated potential sex differences in endocannabinoid (eCB) modulation of Pavlovian fear conditioning and extinction, examining multiple defensive behaviors, including shock responsivity, conditioned freezing, and conditioned darting. We found that while systemic administration of drugs acting on eCB receptors did not influence the occurrence of darting, females that were classified as Darters responded differently to the drug administration than those classified as Non-darters. Most notably, CB1R antagonist AM251 produced an increase in cue-elicited freezing and context generalization selectively in female Non-darters that persisted across extinction and extinction retrieval tests but was prevented by co-administration of TRPV1R antagonist Capsazepine. To identify a potential synaptic mechanism for these sex differences, we next employed biochemical and neuroanatomical tracing techniques to quantify anandamide (AEA), TRPV1R, and perisomatic CB1R expression, focusing on the ventral hippocampus (vHip) given its known role in mediating contextual fear generalization. These assays identified sex-specific effects of both fear conditioning-elicited AEA release and vHip-BLA circuit structure. Together, our data support a model in which sexual dimorphism in vHip-BLA circuitry promotes a female-specific dependence on CB1Rs for context processing that is sensitive to TRPV1-mediated disruption when CB1Rs are blocked.

Predator odor stress reactivity, alcohol drinking and the endocannabinoid system

“…Preclinical work strongly suggests that the endocannabinoid system may directly modulate behavioral aspects of PTSD including fear extinction and contextual stress memory ( Gunduz-Cinar et al, 2023 ; Huckleberry et al, 2023 ; Zabik et al, 2023 ; Crombie et al, 2022 ; Morena et al, 2018 , 2021 ; Mayo et al, 2020 ; Balogh et al, 2019 ; Fidelman et al, 2018 ), and stress coping responses ( Hill et al, 2006 ; McLaughlin et al, 2012 , 2013 , 2014 ; Kondev et al, 2022 , 2023 ; Steiner et al, 2008 ; Gunduz-Cinar et al, 2013 ; Haller et al, 2013 ; Bluett et al, 2017 ; Marcus et al, 2020 ; Berger et al, 2018 ; Pavón et al, 2021 ; Metna-Laurent et al, 2012 ). During fear conditioning, deletion of CB 1 receptors in male mice prevents temporal shift from engagement in freezing behavior to active coping behavior ( Metna-Laurent et al, 2012 ).…”