BEHAVIORAL-RESPONSES OF LABORATORY RATS TO PLAYBACK OF 22 KHZ ULTRASONIC CALLS

It has been demonstrated that cholinergic stimulation of the anterior hypothalamicpreoptic region induces 22 kHz ultrasonic vocalization in rats. Acoustic features of the cholinergically induced vocalization di d not differ from those of 22 kHz calls emitted in natural situations and, therefore, could have a behavioural significance for other conspe cifics. The 22 kHz calls induced by intracerebral injection of carbach ol were played back to rats and their responses were compared with res ponses to playback of 22 kHz calls induced by tactile stimuli and to t hose with background noise. Animal responses were measured by an accel erometric sensor as an average ergometric activity. The average activi ty count was not changed during presentation of acoustic stimuli, howe ver, striking differences were found in animal responses immediately a fter discontinuation of the sound. Activity of the rats consistently a nd significantly decreased after presentation of 22 kHz calls induced by tactile stimuli or by injection of carbachol. Animal responses to c alls induced by carbachol were indistinguishable from responses to cal ls induced by tactile stimuli. No significant changes in the general a ctivity of the animals were observed after presentation of the backgro und noise or during the sessions without stimuli. The results demonstr ate that carbachol-induced ultrasonic calls have behavioural significa nce for other conspecifics and could serve as an alarm call in a simil ar way to naturally produced 22 kHz vocalization.