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 studied. Calls were emitted spontaneously or were induced by an intrahypothalamic-preoptic injection of glutamate. Sonographic analysis of recorded calls revealed that they were within the 35-70-kHz sound frequency range reported for the 50-kHz call type. Systemic amphetamine (AMPH, 2 mg/kg) significantly increased the number of spontaneously emitted 50-kHz calls and the effect of AMPH was dose-dependent. Low dose of intracerebral glutamate (17 microg) had no additive effect on the number of AMPH-induced calls. Higher dose of intracerebral glutamate alone (34 microg) 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 glutamate-induced or spontaneously occurring 50-kHz calls in adult rats are dependent upon dopaminergic transmission. It is postulated that this type of calls may be indicative of dopamine mediated affective state in adult rats.