Hypothalamic temperature and the 22 kHz vocalization of the male rat

Following ejaculation the male rat emits a 22 kHz vocalization that has been hypothesized to play a communicative role. We found previously that this vocalization is often accompanied by rapid and selective hypothalamic cooling, and we hypothesized that the vocalization or, more precisely, the thoracic-laryngeal maneuver underlying the vocalization, is primarily a thermoregulatory behavior. Accordingly, one prediction made herein was that heating the brain of the isolated male, through the infusion of prostaglandin E 2, would be accompanied by the vocalization. Another was that cooling the brain of the copulating male through the injection of sodium salicylate would significantly reduce the post-ejaculatory vocalization. Both predictions were confirmed.