Intraventricular ACTH reduces social interaction in male rats.

Intraventricular ACTH (1.25 microgram), ACTH (1.6 microgram) and ACTH:D-Phe (1.6 microgram) resulted in significant reductions in the time that pairs of male rats spent in active social interaction. This decrease in social behaviour was not accompanied by a decrease in motor activity. The results are similar to those previously found with peripheral administration of ACTH and suggest that these behavioural effects of ACTH are centrally mediated. None of the ACTH fragments had a significant effect on the latency with which thirsty rats started drinking in an unfamiliar environment. The results are discussed in relation to a possible anxiogenic action of ACTH.