The inhibitory effects of
8-OH-DPAT, a 5-HT1A-receptor agonist, and
baclofen, a GABAB-receptor agonist, on
lordosis were examined in
estrogen and
progesterone-treated ovariectomized rats with lesions in either the dorsal raphe nucleus (DRN) or septum and in rats with either
sham lesions or no lesions. The first behavior test series was carried out 6 days after implantation of the rats with
silicon tubes containing
estradiol. Four hours after injection with 0.5 mg
progesterone, behavioral tests were performed before and 30 min after an injection with 1 mg/kg
body weight 8-OH-DPAT. As a result, the mean
lordosis quotient (LQ)s were changed from 100 to less than 20 before and after the injection in all groups. These results suggest that
8-OH-DPAT acts on areas other than the DRN and the septum, leading to a decrease in
lordosis. Two weeks after implantation with
estradiol, the next behavioral test series was carried out after injection with
progesterone. Behavioral tests were performed before and after an injection with 10 mg
baclofen. The results showed that the mean LQs decreased after the injection in all groups, but the mean LQ in the DRN lesion group was higher than that in the
sham groups. These results indicate that
baclofen may act partially on the DRN in inhibiting
lordosis in female rats.