Involvement of the pituitary-adrenal axis in socio-behavioral disturbances after short-term isolation

Short-term social isolation increased socio-explorative behavior of pairs of adult male Wistar rats. Hypophysectomy or adrenomedullectomy did not prevent this increase in social behavior. No differences between 7-day isolated (I) and non-isolated (socially housed, S) animals were observed in basal plasma corticosterone levels and these levels increased to the same level in I- and S-rats during individual exposure to the observation cage. The increase in corticosterone levels found immediately after the social interaction test was higher in I- than in S-rats. When I- and S-rats were tested together, a negative correlation was present between plasma-corticosterone levels and frequencies of social interactions. Blood pressure and heart rate were not affected by the isolation procedure. ACTH1-24 (5 micrograms/100 g) did not affect the frequencies of social interactions, neither in I- nor in S-rats. Although a role for corticosterone in "basal" social behavior could not be excluded, it seems that pituitary-adrenal hormones are not important for the development and expression of socio-behavioral disturbances due to short-term isolation.