Role of Sex and Age on Cardiovascular and Autonomic Responses During Acute and Repeated Restraint Stress in Rats.

In this study we evaluated the influence of sex (male × female adult rats) and age (adult × adolescent × aged male rats) in expression and habituation of the cardiovascular and autonomic responses to restraint stress in rats. For this, arterial pressure, sympathetically-mediated cutaneous vasoconstriction and heart rate (HR) were assessed in Wistar rats during a single (acute) or the 10th session of restraint. We found similar cardiovascular responses during the acute session of restraint stress in male and female animals. Cardiovascular habituation was evident as an accelerated HR return to pre-stress parameters during the recovery of the 10th restraint session and was also similar in both sexes. However, repeated restraint facilitated the sympathetically-mediated cutaneous vasoconstriction in females. Aged rats had reduced blood pressure reactivity during the acute restraint session in relation to male adult rats, whereas adolescents exhibited a facilitated HR return to basal parameters during recovery of the acute restraint. Also, adolescent animals had reduced tachycardiac and pressor responses during the 10th session of restraint stress. Taken together, the findings obtained in this study suggest that cardiovascular reactivity during an acute stress session as well as the habituation of tachycardia identified during repeated exposure to this stressor are sex-independent. However, females might present higher vulnerability to homotypic stressors in relation to males as consequence of an enhanced sympathetic reactivity. Regarding the influence of age, aging seems to limit cardiovascular reactivity during acute stress, whereas cardiovascular habituation processes appear enhanced during adolescence.