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It is well established that the neurotransmitter serotonin participates in the control of sexual behaviour in the male rat. Recently, it has been found that serotonergic activity may either inhibit or facilitate sexual behaviour, depending on the subtypes of serotonin receptors involved. However, the participation of 5-HT2 receptors in the control of male rat copulation has received little experimental attention, and the published data are equivocal. In Experiments 1-4, it was established that the 5- HT2/1C agonist DCI inhibits sexual behaviour in male rats; this inhibition is effectively reversed by the antagonists ritanserin, pirenperone, and ketanserin. Comparison of these effects , with reference to the binding profiles of each drug, provided strong evidence that 5-HT2/1C receptors mediate an inhibitory influence on sexual behaviour in male rats. In addition, a tentative claim may be made that the effects of these drugs may be more attributable to 5-HT2 activity than 5-UT1C activity. ‘Wet dog shake’ behaviour in rats is known to be 5-HT2- dependent. Experiments 5—7 evaluated the novel proposition that the incidence of spontaneous wet dog shaking (WDS) by male rats in mating tests may provide a behavioural assay of concurrent 5—HT2 activity. WDS was found to be associated with copulatory inhibition in noncopulating males, compared to normal copulators, and this relationship was specific to mating situations. Activating 5-HT2/1C receptors with DOl simultaneously induced WDS and inhibited copulation. Thus, the incidence of spontaneous WDS in untreated males may reflect the function of a 5—HT2—mediated neural mechanism that tonically inhibits copulation in male rats. In Experiment 8, DOl microinjection in the nucleus raphe obscurus/inferior olivary complex also induced WDS and inhibited copulation. This suggests that the hypothesized 5- flT2-dependent inhibitory mechanism is vested in the ventromedial brainstem. Recent anatomical findings support this suggestion: cells in this region have bifurcating axons, projecting collaterally to both the medial preoptic area (implicated in sexual behaviour) and to the ventral cervical spinal cord (implicated in WDS). Overall, the results of the eight experiments provide strong evidence that 5-HT2 receptors mediate some of the inhibitory effects of serotonin on male rat sexual behaviour.

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Thesis (Ph. D.)--Lehigh University, 1997. / Includes vita. Bibliography: leaves 136-160.

Thesis (Ph. D.)--Lehigh University, 1997. / Includes vita. Bibliography: leaves 113-118.

Thesis (Ph.D.) - University of St Andrews, March 2009.

Thesis (M.A.)--University of Wisconsin--Madison, 1974. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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. / Arts, Faculty of / Psychology, Department of / Graduate