THE MEL(1A) MELATONIN RECEPTOR GENE IS EXPRESSED IN HUMAN SUPRACHIASMATIC NUCLEI

THE pineal hormone melatonin influences circadian rhythmicity in many vertebrate species. The circadian effects of melatonin in humans have led to its use to treat jet lag and circadian-based sleep disorders. M elatonin is thought to influence circadian rhythmicity by acting in th e suprachiasmatic nuclei (SCN). The recent cloning of two melatonin re ceptor subtypes with high affinity for melatonin allows molecular anal ysis of melatonin receptors in human SCN. We report that Mel(1a) recep tor mRNA is detectable in neonatal human SCN by in situ hybridization. Mel(1b) and melatonin-related receptor mRNAs were not detected. The p resence of Mel(1a) receptor mRNA in human SCN supports the hypothesis that the Mel(1a) receptor is responsible for the circadian effects of melatonin in humans.