title: Median eminence serotonin involved in the proestrus gonadotropin release.
abstract: Numerous studies have suggested that serotonin (5-HT) is involved in the regulation of anterior pituitary hormone release. In the present study, the 5-HT concentrations of the median eminence and anterior pituitary lobe were measured during the estrous cycle and lactation in order to correlate changes in 5-HT levels with changes in serum luteinizing hormone, follicle-stimulating hormone, and prolactin. On the day of proestrus, median eminence 5-HT concentrations declined significantly between 14.00 and 16.30 h at the beginning of the gonadotropin and prolactin surges. No changes in 5-HT concentrations were found between the morning and afternoon on other days of the cycle. In the anterior pituitary, the levels of 5-HT did not change during the estrous cycle. 5-HT turnover rates were also estimated in the median eminence on proestrus and diestrus 1. The median eminence 5-HT synthesis rate increased in the afternoon of proestrus at 16.30 h. 5-HT was also measured in the anterior pituitary and the median eminence of lactating rats in four experimental situations: mothers with their litter until decapitation, mothers separated from their pups 4 h earlier, and mothers separated from their pups 4 h earlier, after which the pups were allowed to suckle for 5 or 30 min. In spite of the acute changes in circulating prolactin, 5-HT levels in the median eminence were not affected in any situation studied. These results suggest that 5-HT in the median eminence is involved in the control of gonadotropin release. The data further suggest that 5-HT does not act directly on the anterior pituitary to modulate gonadotropin or prolactin release.
mesh_terms: D000818:Animals; D004971:Estrus; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007774:Lactation; D007986:Luteinizing Hormone / Q000097:blood; D008473:Median Eminence / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011247:Pregnancy; D011359:Proestrus; D011388:Prolactin / Q000097:blood; D051381:Rats; D012701:Serotonin / Q000502:physiology*
chemical_list: D006065:Gonadotropins, Pituitary; D012701:Serotonin; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone