Abstract:
Ultrasonic vocalizations (USV) are emitted by rats in a number of social situations
such as aggressive encounters, during sexual behavior, and during play in young rats,
situations which are predominantly associated with strong emotional responses. These
USV typically involve two distinct types of calls: 22 kHz calls, which are emitted in
aversive situations and 50 kHz calls, which are emitted in non-aversive, appetitive
situation. The 50 kHz calls are the focus of the present study and to date both the
glutamatergic and the dopaminergic systems have been independently implicated in the
production of these 50 kHz calls. The present study was conducted to examine a possible
relationship between glutamate (GLU) and dopamine (DA) in mediating 50 kHz calls. It
was hypothesized that the dopaminergic system plays a mediating role in 50 kHz calls
induced by injections ofGLU into the anterior hypothalamic/preoptic area (AHPOA) in
adult rats.
A total of 68 adult male rats were used in this study. Rats' USV were recorded
and analyzed in five experiments that were designed to test the hypothesis: in experiment
1, rats were treated with systemic amphetamine (AMPH) alone; in experiment 2, intra-
AHPOA GLU was pretreated with systemic AMPH; in experiment 3, intra-AHPOA GLU
was pretreated with intra-AHPOA AMPH; in experiment 4, rats were treated with high
and low doses of intra-AHPOA AMPH only; in experiment 5, rats were treated with
systemic haloperidol (HAL) as a pretreatment for intra-AHPOA GLU.
Analysis of the results indicated that AMPH has a facilitatory effect on 50 kHz
USV and that a relationship between DA and GLU in inducing 50 kHz calls does exist.
The effect, however, was only observed when DA receptors were antagonized with HAL
and was not seen with systemic AMPH pretreatments of intra-AHPOA GLU. The DAGLU
relationship at the AHPOA was unclear.
