Diurnal rhythm of melatonin binding in the rat suprachiasmatic nucleus

Abstract

We used quantitative in vitro autoradiography to localize and characterize 2125I-melatonin binding sites in the rat suprachiasmatic nuclei in relation to pineal melatonin production. In a lightrdark cycle of 12:12 h, binding density exhibited significant diurnal variation with a peak at the dark-light transition and a trough 12 hours later. Saturation studies suggested that the decreased binding at light-dark transition might be due to a shift of the putative melatonin receptor to a low affinity state. © 1989 by The Endocrine Society.