Inhibitory effect of melatonin on GnRH-induced LH release.
Melatonin inhibits GnRH-induced release of LH and FSH from the neonatal, but not the adult, rat anterior pituitary gland. This action of melatonin is mediated by the specific high-affinity membrane-bound receptors that are absent in adult rats. The intracellular mechanism of melatonin action involves a decrease in intracellular calcium [Ca2+]i in the gonadotrophs; melatonin inhibits GnRH-induced Ca2+ release from endoplasmic reticulum as well as Ca2+ influx through voltage-sensitive channels. Melatonin also inhibits GnRH-induced accumulation of cAMP, which may result in the decreased influx of Ca2+, because cAMP, acting through protein kinase A, stimulates Ca2+ influx into the gonadotrophs. This age-dependent effect of melatonin on gonadotrophin release from the pituitary may be involved in the timing of puberty.
Vanecek
J
J
Institute of Physiology, Academy of Sciences of the Czech Republic, Prague.
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D019204:GTP-Binding Proteins / Q000502:physiology; D007987:Gonadotropin-Releasing Hormone / Q000502:physiology*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D044094:Receptors, Melatonin; D015290:Second Messenger Systems; D014157:Transcription Factors / Q000378:metabolism
D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D014157:Transcription Factors; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D008550:Melatonin; D002118:Calcium