Sex-dependent endocrine, cardiovascular, nociceptive and behavioral responses in rats cohabitating with a conspecific in chronic neuropathic pain

This study aimed to characterize the effects of cohabitation with a same-sex conspecific experiencing chronic neuropathic pain on anxiety-like behavior, mechanical nociception, and both basal and stress-reactive levels of corticosterone, arterial pressure, and heart rate in male and female rats. For this, rats were paired at weaning, and one from each pair (designated demonstrator) underwent chronic constriction injury (CCI) or sham surgery while the cagemate (designated observer) remained undisturbed. Fourteen days later, observer rats were tested for anxiety-like behavior, nociception, cardiovascular parameters and circulating corticosterone levels. We identified that cohabitation with a distressed partner induced mechanical hypernociception and anxiogenic-like effects in both sexes. Although baseline plasma corticosterone levels were unaffected by sex or housing conditions, restraint stress elicited a greater corticosterone response in both sexes cohabiting with a conspecific in pain, with this effect being more pronounced in females. Cardiovascular evaluation showed elevated baseline arterial pressure in both sexes and resting tachycardia only in females. Moreover, females exposed to a conspecific in chronic pain exhibited a blunted tachycardic response to restraint, while the restraint-evoked pressor response and sympathetically-mediated cutaneous vasoconstriction were unchanged by housing condition in either sex. Taken together, these findings demonstrate that cohabitation with a conspecific in chronic pain elicits behavioral, nociceptive, endocrine, and cardiovascular alterations. While most effects were shared between sexes, females displayed heightened vulnerability in physiological domains, particularly in endocrine and cardiac responses, suggesting greater susceptibility to the negative physiological consequences of prolonged social exposure to distress. • Cohabiting with a partner in pain trigged hypernociception in both sexes. • Both sexes also shown anxiety-like behavior after cohabitation. • Pain exposure heightened stress-induced corticosterone, especially in females. • Baseline blood pressure rises in both sexes; heart rate rises only in females. • Females display blunted stress-evoked heart rate increase.