WAY100635 and female rat lordosis behavior

Abstract

Sexually receptive proestrous rats with bilateral cannulae in the ventromedial nucleus of the hypothalamus (VMN) were infused with 200 ng of (±)-8-hydroxy-2-(di- n-propylamino) tetralin (8-OH-DPAT) or with 8-OH-DPAT plus varying concentrations (200 to 2000 ng) of the 5-HT 1A receptor antagonist, N-{2[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}- N-(2-pyridinyl)cyclohexanecarboxamide trihydrochloride (WAY100635). 8-OH-DPAT inhibited lordosis behavior within 15 min of the infusion and every dose of WAY100635 prevented the inhibition. When non-sexually receptive, ovariectomized rats, hormonally primed with 0.5 μg estradiol benzoate and 500 μg progesterone, were infused with WAY100635 (400 to 2000 ng), the 5-HT 1A receptor antagonist did not facilitate lordosis responding. These findings support earlier findings that activation of 5-HT 1A receptors in the mediobasal hypothalamus inhibits lordosis behavior. However, they further demonstrate that tonic activation of 5-HT 1A receptors is not responsible for the absence of sexual receptivity in suboptimally hormonally primed ovariectomized rats.