EFFECT OF 5,7-DIHYDROXYTRYPTAMINE, OVARIECTOMY AND GONADAL-STEROIDS ON SEROTONIN RECEPTOR-BINDING IN RAT-BRAIN

Quantitative autoradiography was used to assess alterations in seroton in (5-HT) receptor binding in the hypothalamus and hippocampus followi ng denervation with 5,7-dihydroxytryptamine (5,7-DHT), ovariectomy (OV X) and gonadal steroid manipulation. Seven days after 5,7-DHT injectio n, 5-HT1a receptor density was significantly increased in the ventrome dial hypothalamic nucleus (VMN) of intact but not OVX femaled rats. Un der these conditions 5-HT1b receptor density was unchanged in any brai n region examined and 5-HT transporter binding was decreased in all 5, 7-DHT injected animals. In addition, there was a significant interacti on between OVX and 5,7-DHT for both the 5-HT1a receptor and the 5-HT t ransporter in the VMN, such that OVX inhibited the 5,7-DHT-induced inc rease in 5-HT1a receptors and attenuated the 5,7-DHT-induced decrease in 5-HT transporter binding. In a separate experiment the effect of go nadal steroid manipulation on 5-HT receptor binding was assessed. In f emale OVX rats, 5-HT1a receptor density was unchanged by estrogen or e strogen and progesterone administration. In male rats, castration sign ificantly decreased 5-HT1a receptor density in the medial preoptic are a. Estrogen and progesterone administration to female OVX rats increas ed the density of 5-HT1b receptors in the VMN, as compared to estrogen alone. The relationship of these results to the role of 5-HT in media ting lordosis behavior is discussed.