Binding characteristics and regional distribution of [125I]iodomelatonin binding sites in the brain of the human fetus.
The binding and pharmacological characteristics of [125I]iodomelatonin binding sites in human fetal brain membrane preparations were determined. Membrane preparations of the whole brain revealed a equilibrium binding constant (Kd) of 17.5 pmol/l with a total number of binding sites (Bmax) at 0.8 fmol/mg protein. Among the various brain regions studied, [125I]iodomelatonin binding was highest in the hypothalamus, and lowest in the mid-brain, pons-medulla, and cerebral cortex. The Kd of the hypothalamus was calculated to be 26.1 pmol/l and the Bmax 5.4 fmol/mg protein. Only 6-chloromelatonin, melatonin and N-acetylserotonin had significant inhibition in the binding. Our results suggest that melatonin receptors are present in the human brain and that melatonin may exert a central action.
Department of Physiology, University of Hong Kong.
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Yuan
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Pang
D001667:Binding, Competitive; D001921:Brain / Q000196:embryology*; D001923:Brain Chemistry; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism; D007211:Indoles / Q000378:metabolism; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000493:pharmacokinetics; D018377:Neurotransmitter Agents / Q000378:metabolism; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D012701:Serotonin / Q000031:analogs & derivatives / Q000378:metabolism
D007211:Indoles; D018377:Neurotransmitter Agents; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; D012701:Serotonin; C024100:6-chloromelatonin; C044556:2-iodomelatonin; D008550:Melatonin; C006389:N-acetylserotonin