The role of the ventral projections of the dorsal raphe nucleus (DRN) in regulating lordosis was examined in female rats. The ventral neural fibers of the DRN were transected by the horizontal circle-cut (VC), anterior (AVC) or posterior half-circle cut (PVC) at the same time as ovariectomy. Three weeks after the surgery, all the rats were implanted with a Silastic tube containing estradiol (E2). The behavioral test was started one day after E2- implantation, and 5 tests in total were carried out every other day. The results showed that the VC females had a higher lordosis quotient (LQ) than control rats. Furthermore, as well as females with the VC, a high score LQ was observed in the AVC rats but not in the PVC females, compared to those in the control animals. These results suggest that the anteroventral neural fibers of the DRN are involved in the lordosis inhibiting mechanisms in female rats.
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