The effect of medial preoptic area lesions on sexually stimulated hormone release in the male rat.

Male rats were subjected to bilateral electrolytic lesions in the medial preoptic area (mPOA). These lesions disrupted sexual behavior without affecting basal levels of luteinizing hormone (LH), prolactin (PRL), or testosterone (T). During exposure to an estrous female, intact and sham-operated rats mated; these rats showed elevations in LH, PRL, and T levels. Lesioned rats, which did not mate, showed elevations in LH but not PRL or T levels. These results demonstrate that the mPOA is not required for sexually stimulated LH release. The failure of lesioned rats to release PRL and T may be secondary to their failure to mate. Alternatively, the mPOA may participate in sexually stimulated PRL release, while T release may depend on prior elevations in both LH and PRL levels. LH release may be related to arousal, and PRL release to consummation, providing a hormonal analogy for the dual mechanism theory of sexual behavior.