High-frequency (35-70 kHz) ultrasonic vocalizations in rats confronted with anesthetized conspecifics: effects of gepirone, ethanol, and diazepam

The effects of three anxiolytics--gepirone, diazepam, and ethanol--on high-frequency ultrasonic vocalizations elicited from rats via a new method are described. Subjects confronted with an anesthetized, same-sex conspecific in a neutral test cage emitted ultrasonic vocalizations in the 35- to 70-kHz range. The great majority of these were calls with frequencies higher than 40 kHz; of these, short calls (< 50 ms) occurred significantly more frequently than long calls (> 50 ms). Female subjects emitted far more of these high-short and high-long vocalizations than males did. In females, but not males, these calls were reduced in number by gepirone, 5-hydroxytryptamine1A (5-HT1A) agonist, at both 1.0- and 10.0-mg/kg doses and by diazepam, a benzodiazepine, at 3.0 but not 1.0 mg/kg. Ethanol (0.6 and 1.2 g/kg) had no detectable effect. The utility of this method, both for the study of ultrasounds and assessment of serotonergic anxiolytics, is discussed.