Effect of melatonin in vivo upon FSH and LH release from hamster pituitary glands.
The effect of chronic daily afternoon injections of melatonin upon basal and melatonin-modulated release of FSH and LH was investigated in superfused hamster anterior pituitary glands. The basal release rate of both FSH and LH began to decline following the beginning of melatonin injections, and reached a nadir after six weeks. Basal release rate of FSH and LH then began to spontaneously increase and reached a plateau at 13 weeks of injections. The inhibition by melatonin upon FSH and LH release in vitro gradually declined during the period of melatonin injections. After six weeks of melatonin injections the release rate of FSH was no longer suppressed by melatonin superfusion, while the release rate of LH became refractory to melatonin suppression in vitro after nine weeks of melatonin injections. These results demonstrate a change in the release rates of both basal and melatonin-inhibited gonadotropin release during melatonin-induced testicular regression and recrudescence in hamsters.
D000818:Animals; D006224:Cricetinae; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D006168:Guinea Pigs; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008647:Mesocricetus; D010477:Perfusion; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors
D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D008550:Melatonin