The role of brain dopamine systems in anticipatory and consummatory aspects of sexual behavior in the male rat
Creators: name: Pfaus, James George
Publisher: name: University of British Columbia
Year: 2011

description: The role of brain dopamine (DA) systems in the control of anticipatory and consummatory aspects of the sexual behavior of male rats was examined in the present experiments. Experiment I explored the statistical relationship among anticipatory and consummatory measures of male sexual behavior using multiple correlations and factor analysis. Level changing, a measure of anticipatory behavioral excitement, was not related statistically to any of the consummatory measures of copulation, whereas several consummatory measures were correlated. The factor analysis revealed the existence of five factors: copulatory rate, initiation, hit rate, mount count, and anticipation; given tentative names based on the measures that loaded most heavily onto each factor. These results established that anticipatory and consummatory measures of male sexual behavior are unrelated statistically. Experiment II examined the dose-response effects of several DA receptor antagonists on anticipatory and consummatory measures of male sexual behavior. Systemic administration of the typical neuroleptics haloperidol and pimozide, and the Dl-selective antagonist SCH 23390, significantly reduced the number of level changes, increased the intromission latencies, and decreased the number of intromissions and the total number of ejaculations. The atypical neuroleptic clozapine and the D2-selective antagonist sulpiride reduced the number of level changes and significantly increased the intromission latencies, but did not affect the number of intromissions or ejaculations. In almost every case, the doses required to reduce level changing were lower than those required to increase the intromission latencies, indicating that the measure of anticipatory sexual behavior was more sensitive to disruption by DA antagonists than were consummatory measures of sexual behavior. The antiemetic agent metoclopramide decreased the number of intromissions but did not affect other anticipatory or consummatory measures of sexual behavior significantly. High doses of haloperidol, pimozide, or clozapine delayed or abolished level changing and the initiation of copulation. These results indicated that anticipatory and consummatory measures of male sexual behavior are affected differentially by DA antagonists. Experiment III provided the first evidence that haloperidol affects anticipatory and consummatory measures of male sexual behavior selectively in different brain DA terminals. Bilateral infusions of haloperidol to the nucleus accumbens reduced level changing without affecting the initiation of copulation or other consummatory measures. Bilateral infusions of haloperidol to the striatum increased the total number of ejaculations but did not affect other consummatory or anticipatory measures. Unilateral infusions of haloperidol to the medial preoptic area (MPOA) produced nearly all of the effects of systemic administration, including reduced number of level changes, increased intromission latencies, and decreased number of intromissions and ejaculations. These results indicated that DA in the nucleus accumbens and striatum are involved in the display of anticipatory sexual behavior and copulatory rate, respectively, whereas DA in the MPOA is involved in anticipatory sexual behavior, the initiation of copulation, and copulatory rate. In Experiment IV, in vivo voltammetry revealed a differential pattern of DA efflux in the nucleus accumbens and striatum, and catecholamine efflux in the MPOA, during anticipatory and consummatory phases of sexual behavior in male rats. Increased DA efflux in the nucleus accumbens and increased catecholamine efflux in the MPOA were associated with the presentation of a receptive female behind a screen and with the initiation of copulation. Efflux in both regions decreased following ejaculation but increased prior to each reinitiation of copulation. DA efflux in the striatum increased nonspecifically during copulation. Use of in vivo microdialysis confirmed the general pattern of DA efflux in the nucleus accumbens and striatum observed with voltammetry. These results were interpreted as supporting a role of DA terminals in the nucleus accumbens and MPOA, but not the striatum, in the display of anticipatory sexual behavior and in the initiation of copulation. In particular, the increased release of DA in the MPOA was viewed as sensitizing hypothalamic mechanisms involved in the control of penile erection whereas the increased release of DA in the nucleus accumbens was viewed as sensitizing motor programs necessary for the execution of anticipatory sexual responses and the initiation of mounting.