THE MELATONIN RECEPTOR IN THE HUMAN BRAIN - CLONING EXPERIMENTS AND DISTRIBUTION STUDIES

The adult human cerebellum expresses melatonin receptors with high den sity in the external zone of the molecular layer. Cloning of the recep tor cDNA isolated by RT-PCR from human cerebellar specimens and sequen cing analysis of the full-length coding region revealed that the recep tor protein is encoded by a transcript identical to that recently clon ed from the human hypothalamus (Mel(1a)). In situ hybridization using an antisense cRNA-probe demonstrated that the melatonin receptor mRNA is localized in the cerebellar granule cells. Mapping of the messenger by RT-PCR with Mel(1a) specific primers in different areas of the hum an brain disclosed a quite widespread distribution of the transcript, although expressed at very low levels. Semi-quantitative comparison be tween the different brain regions allowed to establish the following r elative mRNA abundance: cerebellum greater than or equal to occipital cortex greater than or equal to parietal cortex > temporal cortex > th alamus > frontal cortex greater than or equal to hippocampus. No mRNA was detected in white blood cells.