Ja. Vivian et Ka. Miczek, DIAZEPAM AND GEPIRONE SELECTIVELY ATTENUATE EITHER 20-32 OR 32-64 KHZULTRASONIC VOCALIZATIONS DURING AGGRESSIVE ENCOUNTERS, Psychopharmacology, 112(1), 1993, pp. 66-73
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.