Sex differences in central amygdala glutamate responses to calcitonin gene-related peptide.

Women are disproportionately affected by chronic pain compared to men. While societal and environmental factors contribute to this disparity, sex-based biological differences in the processing of pain are also believed to play significant roles. The central lateral nucleus of the amygdala (CeLC) is a key region for the emotional-affective dimension of pain, and a prime target for exploring sex differences in pain processing since a recent study demonstrated sex differences in CGRP actions in this region. Inputs to CeLC from the parabrachial nucleus (PB) play a causal role in aversive processing, and release both glutamate and calcitonin gene-related peptide (CGRP). CGRP is thought to play a crucial role in chronic pain by potentiating glutamatergic signaling in CeLC. However, it is not known if this CGRP-mediated synaptic plasticity occurs similarly in males and females. Here, we tested the hypothesis that female CeLC neurons experience greater potentiation of glutamatergic signaling than males following CGRP exposure. Using trains of optical stimuli to evoke transient CGRP release from PB terminals in CeLC, we find that subsequent glutamatergic responses are preferentially potentiated in CeLC neurons from female mice. This potentiation was CGRP-dependent and involved a postsynaptic mechanism. This sex difference in CGRP sensitivity may explain sex differences in affective pain processing.