The Mel1a 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. Melatonin is thought to influence circadian rhythmicity by acting in the suprachiasmatic nuclei (SCN). The recent cloning of two melatonin receptor subtypes with high affinity for melatonin allows molecular analysis of melatonin receptors in human SCN. We report that Mel1a receptor mRNA is detectable in neonatal human SCN by in situ hybridization. Mel1b and melatonin-related receptor mRNAs were not detected. The presence of Mel1a receptor mRNA in human SCN supports the hypothesis that the Mel1a receptor is responsible for the circadian effects of melatonin in humans.