Corticosterone and prolactin do not mediate alarm pheromone effect in the rat

Corticosterone and prolactin do not reflect the alarm pheromone effect in the rat. Male rats were immersed in water previously swum in by 0, 1, or 2 other rats. Immobility decreased considerably after immersion in water previously swum in by one animal and did not decline further because of a "floor effect." Plasma corticosterone levels were increased by immersion in both fresh and soiled water. Prolactin levels were not increased significantly. Water condition did not significantly affect plasma corticosterone or prolactin levels when rats were sacrificed immediately after testing or 20 min after testing. These results indicate that neither corticosterone nor prolactin mediate the alarm pheromone phenomenon.