Effects of the 5-HT1A agonist, 8-OH-DPAT, on sexual behaviors of the proestrous rat.

The effects of the 5-HT1A agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), were examined in intact, proestrous rats. Although this compound has been reported to inhibit sexual receptivity of hormonally primed, ovariectomized rats, this is the first report of its effect in intact females. After intraperitoneal treatment with 8-OH-DPAT (0.01 to 0.25 mg/kg), there was a dose-dependent suppression of lordosis behavior. The inhibition occurred within 10-15 min after the higher doses and lasted at least an hour after treatment. When females were treated with 1 mg/kg trifluoromethylphenyl piperazine (TFMPP) 30 min prior to treatment with 0.1 mg/kg 8-OH-DPAT, females recovered more rapidly from the inhibitory effects of 8-OH-DPAT. After bilateral, intrahypothalamic infusion of 50 to 1000 ng 8-OH-DPAT, inhibition of sexual behavior resembled that seen following systemic treatment with 0.1 mg/kg 8-OH-DPAT, females recovered more rapidly from the inhibitory effects of 8-OH-DPAT. After bilateral, intrahypothalamic infusion of 50 to 1000 ng 8-OH-DPAT, inhibition of sexual behavior resembled that seen following systemic treatment. Cannula locations in the ventromedial hypothalamus, but not the posterior hypothalamus, produced rapid inhibition of lordosis behavior. Both the frequency and the quality of lordosis behavior were reduced within 5 to 10 min after bilateral infusion of 200 to 1000 ng (but not 50 ng) 8-OH-DPAT, and females often successfully avoided attempted mounts by the male. These results suggest that activation of ventromedial hypothalamic 5-HT1A receptors reduces lordosis behavior.