Differential Effects of Dorsal Raphe Nucleus Lesions on Pseudopregnancy Induced by Reserpine or Vaginal Stimulation in Female Rats

Abstract

The role of the dorsal raphe nucleus in the maintenance of pseudopregnancy induced by reserpine and/or vaginal stimulation was investigated in female rats. In order to induce pseudopregnancy, either the vagina was stimulated electrically (VS) on the day of proestrus, or 1 mg/kg b.w. reserpine (R) was injected on the day of diestrus I. In some females, both VS and R treatments (VS+R) were applied. Radiofrequency lesions were made in the dorsal raphe nucleus (DRL) 5 days after VS and 3 days after R. At the same time, the left uterine horn was traumatized in order to induce deciduoma. As a result, positive decidual responses were seen in most control and sham-control rats with VS or R-treatments. In contrast, the incidence of deciduoma in DRL females with R injection was lower than that in control and sham groups, but the incidence in DRL females with VS or VS+R was comparable to that in control and sham females. These results suggest that the dorsal raphe nucleus plays an important role in maintaining the mechanism of pseudopregnancy induced by reserpine, but not in that induced by vaginal stimulation.