DIAZEPAM AND GEPIRONE SELECTIVELY ATTENUATE EITHER 20-32 OR 32-64 KHZULTRASONIC VOCALIZATIONS DURING AGGRESSIVE ENCOUNTERS

Ultrasonic vocalizations (USV) in rats may communicate ''affective'' s tates, as they occur only in highly significant behavioral contexts su ch as during sex, aggression, exposure to painful or startling events. This proposal was evaluated in an experiment with adult male Long-Eva ns rats during agonistic encounters; specifically, the effects of diaz epam, flumazenil and gepirone were studied on different types of USV e mitted by intruder rats exposed to resident attacks and to ''threat of attacks'' (i.e., intruder protected within the home cage of the resid ent by a wire mesh cage). USV were readily emitted during agonistic en counters and consisted primarily of two distributions of pure tone whi stles: 0.3- to 3-s, 20- to 32-kHz (''low'') signals and 0.02- to 0.3-s , 32- to 64-kHz (''high'') signals. A considerable repertoire of frequ ency modulated signals was observed and proved to be sensitive to the anxiolytic treatments. Diazepam (1-6 mg/kg) dose-dependently decreased high frequency USV during the threat of attack and decreased the mean pitch of the most predominant vocalizations but did not affect low fr equency USV or the audible squeals (AS) in response to bites. Gepirone (0.3-6 mg/kg) dose-dependently decreased low frequency USV and did no t affect high frequency USV or AS. Responses to thermal pain stimuli r emained unaltered by all drugs, while walking duration was decreased a nd crouch postures were increased after diazepam but not after gepiron e administration. Gepirone in the present dose range had minimal effec ts on submissive, exploratory and locomotor behaviors. The pattern of results is consistent with the proposal that low frequency USV reflect a heightened affective state which is ameliorated with 5HT1A but not benzodiazepine anxiolytics, and suggests that the suppression of high frequency USV in reaction to attacks or threats coincides with the sed ative or muscle relaxant properties of these compounds.