Intracerebral actions of the 5-HT 1A agonists, 8-OH-DPAT and buspirone and of the 5-HT 1A partial agonist/antagonist, NAN-190, on female sexual behavior

Abstract

Proestrous rats were infused intracerebrally with 50–1000 ng 8-OH-DPAT, 500 or 2000 ng buspirone or 125–500 ng NAN-190. For each drug, bilateral infusions into the mediobasal hypothalamus inhibited female lordosis behavior and proceptivity and initiated resistive behavior. The effects of the drugs were evident within 5–20 min of infusion and generally lasted for 1–2 hr. The effective sites for 5-HT 1A-mediated inhibition of sexual behavior were most concentrated in the ventromedial nucleus of the hypothalamus. Cannulae sites anterior, posterior or dorsal to the ventromedial nucleus or clearly within the IIIrd ventricle were less effective at disrupting lordosis behavior. The inhibition of sexual behavior, following 8-OH-DPAT occurred in a dose-dependent manner and appeared to include the loss of motivation of the female to mate. Buspirone produced similar, but quantitatively smaller, effects on lordosis behavior. NAN-190 slightly, but significantly, suppressed lordosis behavior after either intracerebral or intraperitoneal injection and substantially increased resistive behavior. These results suggest that the inhibition of lordosis behavior, following treatment with 5-HT 1A agonists, include an action within the ventromedial nucleus. Moreover, 5-HT 1A receptors in this area appear to play a functionally important role in the modulation of the female's “willingness” to mate.