Changes in serum corticosterone and testosterone during induced maternal behavior in rats.

Serum corticosterone (Cpd B) and testosterone (T) concentrations were studied during the avoidance phase of artificially induced parental behavior in male rats. Adult rats were exposed to the presence of standard size foster pups for 60 min daily. On day 1 the avoidance behavior characterized by typical burying reaction was accompanied by an elevation of Cpd B and T. The behavioral responses and hormonal changes diminished during the days of repeated exposure. It was found that neither pup-killing nor spontaneous retrieval were dependent on circulating hormones in the male rat. Subcutaneous injection of ACTH 4-10 inhibited extinction of the avoidance and the humoral responses in both female and male animals. Oxytocin failed to exert any influence on the behavioral and hormonal components of the aversive reaction.