title: Melatonin receptors are present in the ferret pars tuberalis and pars distalis, but not in brain.
abstract: The pineal hormone melatonin regulates reproductive function in seasonally breeding mammals. Recent studies using 125I-labeled 2-iodomelatonin (I-MEL) reveal that the distribution of putative melatonin receptors is species-specific; only the hypophysial pars tuberalis (PT) is a consistent site of I-MEL binding in all photoperiodic species examined. In the present study, we used in vitro autoradiography to examine the distribution of I-MEL binding in the ferret brain and pituitary. We report that I-MEL binding is restricted to the PT and pars distalis (PD) of the pituitary; I-MEL binding is absent from brain. I-MEL binds in the PT and PD with high affinity (Kd values ca. 40 pM) and the rank order of potency for inhibition of I-MEL binding (6-chloromelatonin = melatonin greater than 6-hydroxymelatonin greater than N-acetylserotonin greater than serotonin) is the same as that observed for high-affinity melatonin receptors from other species. The consistent presence of high affinity melatonin receptors in the PT of a variety of photoperiodic species suggests that the PT plays a major role in mediating the effects of melatonin on neuroendocrine function.
authors.affiliation: Laboratory of Developmental Chronobiology, Children's Service, Massachusetts General Hospital, Boston.
authors.forename: D R
authors.initials: DR
authors.lastname: Weaver
authors.forename: S M
authors.initials: SM
authors.lastname: Reppert
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D005260:Female; D005289:Ferrets / Q000378:metabolism*; D008550:Melatonin / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism*; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; D008550:Melatonin