EFFECTS OF CHRONIC LESIONS IN MESENCEPHALIC RAPHE NUCLEI ON INDUCTIONOF PSEUDOPREGNANCY

The role of mesencephalic raphe nuclei in the induction of pseudopregn ancy was investigated in female rats. The dorsal or median raphe nucle us lesions (DRL or MRL, respectively) were made by means of a radiofre quency lesion generator. Two or 3 weeks after the operation, in order to induce pseudopregnancy, the vagina was stimulated electrically on t he day of proestrus or 1 mg/kg b.w. reserpine was injected on the day of diestrus I. Traumatization by passing thread to one uterine horn wa s performed to induce deciduoma 5 days after vaginal stimulation or 3 days after reserpine injection. As the results, decidual response was seen in most control and sham females in both vaginal stimulation and reserpine-treated groups. In contrast, incidences of deciduoma in DRL females with vaginal stimulation or reserpine-injection were significa ntly lower than those in control and sham groups. In the MRL females w ith either vaginal stimulation or reserpine-treatment, incidences of d eciduoma were comparable to those of the control and sham operated gro ups. These results suggest that the dorsal raphe nucleus plays an impo rtant role in pseudopregnancy-inducing mechanisms in female rats.