Serotonergic lesions decrease μ- and δ-ipiate receptor binding in discrete areas of the hypothalamus and in the midbrain central gray

Serotonergic nerve terminals in the brain were lesioned by intraventricular infusion of the selective neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) and levels of μ- and δ-opiate binding were measured in brain areas implicated in reproductive behavior and gonadotropin secretion. The lesion decreased μ-receptor binding in the preoptic area (mPOA) and the midbrain central gray, while δ-receptor binding was decreased in the mPOA and the dorsomedial nucleus of the hypothalamus. Hypothalamic serotonergic lesions also attenuated morphine inhibition of female sexual behavior. These results indicate the existence of serotonergic-opiate interactions in select regions of the brain and suggest that these interactions may be important in the regulation of lordosis behavior.