Isolamento sociale nel ratto adolescente:differenze di genere nella sensibilità allo stress ed influenza sulla generazione successiva

Social isolation in male rats at weaning results in reduced basal levels of the neuroactive steroid allopregnanolone (AP) in the brain and plasma as well as in increased anxiety-like behavior. Moreover, social isolation induced an enhanced neurosterogenesis in response to acute stressful stimuli and impairs negative feedback regulation of HPA axis. Socially isolated female rats also manifest a reduced basal cerebrocortical concentration of AP as well as an anxiety-like profile in the elevated plus-maze and Vogel’s conflict tests compared with group-housed controls. At variance, socially isolated female showed less sensitivity the acute stress induced by foot-shock: there was no significant change in the plasma and brain concentration of AP, and an attenuation of corticosterone release. The basal level of corticotrophin releasing factor (CRF) was not changed by social isolation, however, we found that the CRF receptor type 1 in the pituitary was significantly decreased compared to group-housed. Immunoblot analysis revealed that hippocampal abundance of glucocorticoid receptors was significantly higher in the socially isolated female rats; on the contrary, social isolation significantly decreased mineralocorticoid receptors in the same brain area. The effect of social isolation was also evaluated in the neuroendocrine profile during pregnancy and in the quality of maternal care. The pattern of plasmatic variations of 17b-estradiol, oxytocin and vasopressin was not different in the two groups of rats. The analysis of maternal behavior revealed that socially isolated dams displayed less arched-back nursing than control across all day of the observation period. Despite the fact that they were raised under normal conditions, adult male offspring of male and female rats subjected to social isolation before mating exhibited an increased basal cerebrocortical level of AP. These animals also showed a blunted corticosterone release induced by foot-shock stress compared to group-housed offspring. Moreover, the exposure to a chronic stress (social isolation) failed to decrease plasma AP levels in socially isolated offspring. The results indicate that there are same sex differences in the effect of social isolation and that offspring of socially isolated parents can be classified as a resilient. �