Effect of 5,7-Dihydroxytryptamine, Ovariectomy and Gonadal Steroids on Serotonin Receptor Binding in Rat Brain

Abstract

Quantitative autoradiography was used to assess alterations in serotonin (5-HT) receptor binding in the hypothalamus and hippocampus following denervation with 5, 7-dihydroxytryptamine (5, 7-DHT), ovariectomy (OVX) and gonadal steroid manipulation. Seven days after 5, 7-DHT injection, 5-HT_1a receptor density was significantly increased in the ventromedial hypothalamic nucleus (VMN) of intact but not OVX femaled rats. Under these conditions 5-HT_1b receptor density was unchanged in any brain region examined and 5-HT transporter binding was decreased in all 5, 7-DHT injected animals. In addition, there was a significant interaction between OVX and 5, 7-DHT for both the 5-HT_1a receptor and the 5-HT transporter in the VMN, such that OVX inhibited the 5, 7-DHT-induced increase in 5-HT_1a receptors and attenuated the 5, 7-DHT-induced decrease in 5-HT transporter binding. In a separate experiment the effect of gonadal steroid manipulation on 5-HT receptor binding was assessed. In female OVX rats, 5-HT_1a receptor density was unchanged by estrogen or estrogen and progesterone administration. In male rats, castration significantly decreased 5-HT_1a receptor density in the medial preoptic area. Estrogen and progesterone administration to female OVX rats increased the density of 5-HT_1b receptors in the VMN, as compared to estrogen alone. The relationship of these results to the role of 5-HT in mediating lordosis behavior is discussed.

Serotonin 5-HT_1A Receptor mRNA Expression in Dorsal Hippocampus and Raphe Nuclei after Gonadal Hormone Manipulation in Female Rats

“…In contrast, short-term administration of estradiol does not seem to affect 5-HT 1A gene expression or binding in the hippocampus [16, 17, 18, 19]. In a recent study by Österlund et al [22], 2 weeks of estradiol administration decreased 5-HT 1A receptor binding in several hippocampal subregions with unaltered 5-HT 1A receptor mRNA levels.…”

“…Several studies have investigated the effect of short-term gonadal hormone manipulation on serotonin receptor expression in the rat brain, although with discordant results [16, 17, 18, 19]. In contrast, data are very sparse concerning effects of chronic gonadal hormone manipulation [20, 21, 22], including effects of combined estradiol and progesterone supplementation.…”

Ovarian Steroid Regulation of 5-HT1A Receptor Binding and G protein Activation in Female Monkeys

“…Depending on the area examined and the treatment regimen, postsynaptic 5-HT 1A receptor binding sites have been reported to increase (Flugge et al 1999), decrease (Osterlund et al 2000), or not change (Clarke and Maayani 1990;Frankfurt et al 1994). Studies on ovarian steroid regulation of 5-HT 1A autoreceptor binding in rodents are lacking.…”

Neurobiology of Sexual Desire

“…The relationship between serotonin and lordosis behavior in female rats is well documented (Frankfurt et al, 1994), indicating an inhibitory role of serotonin in female sexual behavior such as lordosis response (Allen et al, 1993;Uphouse, 2000).…”