Cardiovascular physiology and anxiety-like behaviors are impacted by repeated restraint stress in a sex-dependent manner

Abstract

Cardiovascular (CV) disease risk is increased by emotion and stress-induced increases in heart rate (HR) and blood pressure (BP), especially in women. Men and women exhibit dissimilar CV responses to anxiety, which suggests that the neurocircuits involved may be sexually distinct. Stress and anxiety-induced CV responses are modulated by the basolateral amygdala (BLA) which displays sex differences in activity and hyperactivation of the BLA coincides with anxiety and increased risk for adverse CV events. The bed nucleus of the stria terminalis (BNST) receives BLA innervation and also regulates CV responses during anticipatory anxiety. We demonstrated that BLA neurons projecting to the BNST (BLA-BNST) facilitate anxiety-like behaviors in males, but not females suggesting that this pathway is more active in males and may contribute to sex differences in anxiety-induced CV responses. This led to our hypothesis that repeated restraint stress would augment anxiety-like behaviors and anxiety-induced CV responses in female rats to a greater degree than males. To test this, rats underwent repeated restraint stress (20 min/day for 7 out of 9 days) while control rats remained in their home cages. Stress rats gained significantly less weight (*P=0.045) and had larger adrenal glands (*P=0.042), suggesting that repeated restraint stress was a comparable stressor between the sexes. Following treatment, rats were conditioned to a long duration tone while receiving 5 random footshocks. Four days later, in a novel context, rats were exposed to the tone alone and time spent freezing was measured as an indicator of anticipatory anxiety. We observed a trend for stressed female rats to freeze more during testing compared to control females (P=0.11), but no differences in males. Additionally, when we quantified other behaviors during prolonged cued fear conditioning (e.g. darting) we found a robust interaction between sex and stress on time spent on hind limbs (*P=0.023) and a trend for scanning (P=0.070) during testing with stress males spending more time performing these behaviors compared to controls and stress females spending less time doing these behaviors compared to their controls. This suggests that stress has sex specific effects on anxiety-like behaviors. In order to determine the CV consequences of stress, a subset of male rats (N=5) were implanted with radio telemetry to enable HR and BP recordings in awake and freely moving rats. Preliminary results from this study suggest that restraint stress increases resting BP in male rats compared to controls. Furthermore, stress rats also had enhanced BP and HR responses to predator odor exposure and social interaction with a novel rat compared to controls. Together, these data suggests a link between CV responses to anxiety and stress, but further studies including females are necessary to determine if stress-induced sex differences observed in anxiety-like behavior are directly linked to CV responses. Funded by National Institutes of Health (R01MH100536) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.