Aversive 22-kHz ultrasonic vocalization playback reveals differences in affective (dys)function following early life adversity in male and female juvenile rats.

Early life adversity (ELA), such as childhood neglect, is a significant risk factor for the development of anxiety and other disorders characterized by affective dysfunction, with worse outcomes in women/girls. Rodent models of ELA, such as maternal separation, show comparable behavioral and neural correlates to patient populations. Despite this, many behavioral assays aimed at understanding affective processing in rodents lack species-specific relevance and are therefore limited in translational application. To address this, we utilized an ethologically relevant rat-specific cue of potential threat - aversive 22-kHz ultrasonic vocalization (USV) playback - within the open field test (OFT) to probe changes in affective processing in juvenile male and female rats following ELA. In control reared rats, measures of locomotion and center exploration revealed significant anxiogenic effects of 22-kHz USV playback compared to silence. These effects were exacerbated by ELA, where ELA reared females demonstrated even greater indices of USV-evoked anxiety-like behavior than standard-reared controls. As prior research has indicated a role for parvalbumin (PV) containing inhibitory neurons in regulating affective behaviors, we quantified changes in PV cell recruitment (via c-Fos co-expression) in two regions important for processing threat: prefrontal cortex (PFC) and basolateral amygdala (BLA). Results showed region-specific effects of ELA and 22-kHz USV playback on the recruitment of PV neurons within the BLA and infralimbic PFC, which differed between males and females. Together, these findings suggest that 22-kHz USVs as a probe is a sensitive measure of ELA-induced affective dysfunction, and that these behavioral changes may be associated with PV activity within the infralimbic PFC and BLA.