title: The ontogeny of 2-[125I]iodomelatonin binding sites in chicken brain.
abstract: The characteristics of the binding sites for 2-[125I]iodomelatonin were studied in chicken brain membranes during development. Specific binding, defined using cold melatonin (1 microM), was detected as early as 8-day-old embryos. Scatchard analysis of saturation experiments showed that 2-[125I]iodomelatonin binds to a single class of site at all ages tested (8-day-old embryos to 3-month-old chicks). Binding affinity (Kd) did not change during development (18-31 pM), but the maximal number of binding sites (Bmax) increased until embryonic day 18, and then remained relatively constant until 30 days of age. A further increase in Bmax was seen at 3 months of age. Guanosine 5'-triphosphate (GTP, 1 mM) inhibited 2-[125I]iodomelatonin binding at all ages suggesting that the melatonin binding site is coupled to a guanine nucleotide binding protein at a very early stage of development. Competition experiments with a number of melatonin analogues indicated that the binding site detected in the brain at embryonic day 8 was pharmacologically identical to that observed 15 days after hatching.
authors.affiliation: Physiology Group, Biomedical Sciences Division, King's College, London, UK.
authors.forename: N W
authors.initials: NW
authors.lastname: Chong
authors.forename: D
authors.initials: D
authors.lastname: Sugden
mesh_terms: D000375:Aging; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D002642:Chick Embryo; D002645:Chickens; D007457:Iodine Radioisotopes; D007700:Kinetics; D008550:Melatonin / Q000378:metabolism*; D009928:Organ Specificity; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; D008550:Melatonin