Facilitation of sexual behavior shortly after electrolytic lesion of the medial preoptic area: what does it mean?

To analyze the behavioral effects of an unphysiological manipulation of the medial preoptic area (MPOA), sexually experienced male rats received small bilateral electrolytic lesions within this area. Thirty-five percent of the lesioned animals showed a drastic facilitation of sexual behavior when tested 3 h after lesion. The number of intromissions, ejaculation latency, and postejaculatory interval were drastically reduced. The mean number of ejaculations was significantly higher in lesioned animals that displayed the behavior in comparison both to an intact group and a sham-lesioned group. Neither the size of the lesion nor its exact location could be correlated with the facilitation of sexual behavior. However, animals that showed facilitation tended to have the lesion located in the ventral part of the MPOA. Lesions rostral or dorsal to the MPOA were ineffective. It is suggested that the small electrolytic lesions in the MPOA produced iron deposits that stimulated the remaining intact preoptic region, resulting in the drastic facilitation of sexual behavior. The results of the present study support the hypothesis suggesting that the MPOA is involved in the mechanisms related to the initiation and execution of sexual behavior.