Sex differences in dendritic atrophy of CA3 pyramidal neurons in response to chronic restraint stress

The present study investigated the effects of 21 days of chronic restraint stress on neural and endocrine parameters in male and female rats. Consistent with previous results, repeated restraint stress induced apical dendritic atrophy (a decrease in the number of apical branch points and dendritic length) of the CA3c pyramidal neurons in male rats. In contrast, female rats did not show significant dendritic atrophy in the apical field in response to repeated restraint stress. Female rats did show a decrease in the number of branch points in the basal dendritic tree compared to male rats in response to repeated restraint stress. Baseline and stress levels of plasma corticosterone were higher in female rats compared to male rats. Females exhibited slightly longer increases in corticosterone levels throughout the 21 days of restraint stress than males, indicating that the male corticosterone response to stress exhibited greater habituation. Plasma corticosteroid-binding globulin levels of female rats were also higher than those of male rats throughout the experiment. There was no change in plasma corticosteroid-binding globulin levels in male rats during the restraint stress, while there was a decrease in plasma corticosteroid-binding globulin levels in female rats during the restraint stress. Plasma estradiol levels in female rats also decreased in response to the chronic stress. In view of the qualitatively different dendritic atrophy found in males and females in appears unlikely that sex differences in the corticosteroid-binding globulin and corticosterone response can account for these morphological differences.