The related roles of dopamine and glutamate in the initiation of 50-kHz ultrasonic calls in adult rats

Effects of amphetamine on the production of 50-kHz ultrasonic calls were st udied. Calls were emitted spontaneously or were induced by an intrahypothal amic-preoptic injection of glutamate. Sonographic analysis of recorded call s revealed that they were within the 35-70-kHz sound frequency range report ed for the 50-kHz call type. Systemic amphetamine (AMPH, 2 mg/kg) significa ntly increased the number of spontaneously emitted 50-kHz calls and the eff ect of AMPH was dose-dependent. Low dose of intracerebral glutamate (17 mug ) had no additive effect on the number of AMPH-induced calls. Higher dose o f intracerebral glutamate alone (34 mug) significantly increased the number of 50-kHz calls, which was completely reversed by systemic application of haloperidol (2 mg/kg), a dopamine antagonist. The results suggest that glut amate-induced or spontaneously occurring 50-kHz calls in adult rats are dep endent upon dopaminergic transmission. It is postulated that this type of c alls may be indicative of dopamine mediated affective state in adult rats. (C) 2001 Elsevier Science Inc. All rights reserved.