Abstract
Melatonin (MLT) is rhythmically secreted from the pineal gland and acts on two G protein‐coupled receptors, termed MT1 and MT2. Brain tissue from a transgenic mouse line expressing red fluorescence protein (RFP) at the MT1 receptor promoter provides a method of localizing the receptor. RFP‐MT1 fluorescence and immunoreactivity was localized to the medial habenula (MHb), habenula commissure (HbC) and the midbrain dorsal medial periaqueductal grey (DMPAG) area. The habenula acts as a relay station from forebrain to midbrain. The downstream PAG plays a prominent role in pain transmission (Behbehani, Prog Neurobiol 1995;46:575–605). The goal of our research is to investigate the distribution of the MT1 receptor in these cholinergic, dopaminergic and glutamatergic neuronal systems. Immunofluorescence co‐staining for RFP along with choline acetyl transferase (ChAT), tyrosine hydroxylase (TH) or vesicular glutamate transporter (VGLUT2) is used to investigate the distribution of the MT1 receptor. Results show RFP‐MT1 expression in the dorsal MHb, clearly separated from ChAT staining in the ventral MHb. TH colocalized with RFP‐MT1 in the HbC, PAG, and the ependymal lining of the aqueduct. VGLUT2 and RFP‐MT1 positive cells are present in dorsal MHb neurons. These results indicate a possible role for the MT1 receptor in the modulation of glutamatergic and dopaminergic neurotransmission. Supported by DA 021870 MLD.
Published Version
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