A MARKED DIURNAL RHYTHM OF MELATONIN ML1A RECEPTOR MESSENGER-RNA EXPRESSION IN THE SUPRACHIASMATIC NUCLEUS

Melatonin (ML1A) receptor binding in the suprachiasmatic nucleus (SCN) exhibits a diurnal rhythm, with significant increases during the dayt ime. In order to determine whether the diurnal variation in binding is reflected by a cycling of melatonin ML1A receptor mRNA levels, we uti lized a semiquantitative reverse transcriptase-polymerase chain reacti on procedure to examine receptor expression throughout the light-dark cycle. Here we report the first evidence of a significant diurnal vari ation in ML1A receptor mRNA levels within the SCN. Furthermore, this m RNA expression occurs similar to 3 h prior to, but is tightly correlat ed to the diurnal rhythm in high-affinity melatonin binding in the SCN . (C) 1997 Elsevier Science B.V.