Melatonin binding sites.
The distribution and characterization of specific melatonin binding sites were studied using 125I-melatonin. Autoradiography revealed only three sites of specific melatonin binding in brain: the suprachiasmatic nuclei, the median eminence, and the small part of choroid plexus at the caudal end of the fourth ventricle. Two other sites were detected outside the CNS: the anterior pituitary and the retina. The specific binding of 125I-melatonin was saturable and reversible. The dissociation constant (KD) of the binding sites was 60 pM. The concentration of the binding sites (Bmax) in the median eminence was 26 fmol/mg protein, and in the pituitary 3 fmol/mg protein. Specificity of the binding sites was tested by displacement of 125I-melatonin. The order of potency--melatonin much less than N-acetyl-5-hydroxytryptamine less than 5-methoxytryptamine much less than 5-hydroxytryptamine = 3,4-dihydroxyphenylethylamine = noradrenaline--shows high specificity of the binding sites for melatonin.
Vanĕcek
J
J
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002831:Choroid Plexus / Q000378:metabolism; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D008473:Median Eminence / Q000378:metabolism; D008550:Melatonin / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013493:Suprachiasmatic Nucleus / Q000378:metabolism
D007457:Iodine Radioisotopes; D008550:Melatonin