Intrahypothalamic 5,7-dihydroxytryptamine: temporal analysis of effects on 5-hydroxytryptamine content in brain nuclei and on facilitated lordosis behavior.
The long-term relationship between serotonin (5-HT) levels in discrete hypothalamic nuclei and female rat sexual behavior, the lordosis response, was examined following intrahypothalamic injection of 5,7-dihydroxytryptamine (5,7-DHT). One week following 5,7-DHT injection, 5-HT levels in the ventromedial hypothalamic nucleus, dorsomedial nucleus, anterior hypothalamic nucleus and the medial preoptic nucleus were approximately 90% depleted as compared to sham animals. Other hypothalamic and preoptic areas including the arcuate-median eminence, vertical nucleus of diagonal band and lateral septal nucleus showed smaller reductions in 5-HT, from 40 to 70% of sham values. At this time estrogen-dependent lordosis behavior in the lesioned group was facilitated. Behavioral facilitation was greatest at 4 weeks post lesion when depletion of 5-HT in the VMN was maximal. 5-HT levels increased at 57 days after 5,7-DHT treatment in most areas, and by 71 days post lesion, no significant differences in 5-HT levels were found between sham and 5,7-DHT-treated groups. Concomitant with the increases in 5-HT, facilitated lordosis behavior gradually decreased. Loss of behavioral facilitation appeared to be most closely related to increases in content of 5-HT in the ventromedial nucleus. These results further support the hypothesis that 5-HT endings in the hypothalamus exert tonic inhibitory regulation over hormone-dependent lordosis in the female rat. They also indicate that regenerating 5-HT fibers in the hypothalamus can reinstate a normal pattern of hormone-dependent behavioral function.
D015116:5,7-Dihydroxytryptamine / Q000008:administration & dosage* / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004102:Dihydroxytryptamines / Q000008:administration & dosage*; D004298:Dopamine / Q000378:metabolism; D005260:Female; D007031:Hypothalamus / Q000187:drug effects*; D007276:Injections, Intraventricular; D009638:Norepinephrine / Q000378:metabolism; D011187:Posture; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D012726:Sexual Behavior, Animal / Q000187:drug effects*; D013997:Time Factors
D004102:Dihydroxytryptamines; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D004298:Dopamine; D009638:Norepinephrine