The pituitary mediates production or release of an alarm chemosignal in rats.

Rodent alarm chemosignals elicit various behavioral and physiological responses in conspecifics. This study employed a bioassay method, using a modification of the forced swim test, to demonstrate that the pituitary mediates production and/or secretion of an alarm chemosignal in rats subjected to stress. This was shown by comparing the immobility times of rats in water soiled by hypophysectomized and sham-treated rats. Rats tested in water soiled by sham-treated rats exhibited very little immobility (the alarm chemosignal effect), whereas rats tested in water soiled by hypophysectomized rats exhibited considerably more immobility. The alarm chemosignal effect was restored in hypophysectomized rats by administration of ACTH. This is the first study to identify mediation of an alarm chemosignal in mammals.