Studies on the Role of the Medial Preoptic Area in Sexual Behavior and Hormonal Response to Sexual Behavior in the Mature Male Laboratory Rat1

Abstract

The role of the medial preoptic area (MPOA) in the regulation of plasma LH, prolactin and testosterone during mating in the male Sprague-Dawley rat was examined. Electrochemical stimulation of the MPOA caused both LH and testosterone to rise significantly within 5 and 40 min,respectively. Although lesions of the MPOA resulted in the loss of sexual behavior, basal levels of plasma LH and prolactin remained unchanged in the MPOA lesioned rat, while a rise in basal levels of plasma testosterone was inconsistent. However, the rise of plasma LH and testosterone persisted in the lesioned rat during exposure to an estrous female, but the rise of plasma prolactin did not. The ability to release prolactin when stressed with ether was nevertheless retained. Administration of LHRH, either intracranially or s.c., had little effect on recovery of sexual behavior in lesioned animals nor was sexual behavior in the sham lesioned animal enhanced by such treatment. It was concluded that while the MPOA is essential to sexual behavior, it is not directly involved in regulation of the hormonal response of LH and testosterone during mating. However, either the MPOA is necessary for the prolactin surge during mating or this surge is regulated independently of the MPOA and responds only to actual participation in sexual behavior. It is suggested that this fractionation of the hormonal response to the estrous female may represent the hormonal counterpart to the conceptual fractionation of sexual behavior into its arousal and consummation components.