CELLULAR-LOCALIZATION OF NA+ MYO-INOSITOL COTRANSPORTER MESSENGER-RNAIN THE RAT-BRAIN/

THE distribution of Na+/MYO-inositol co-transporter(SMIT) mRNA in the rat brain was studied by in situ hybridization histochemistry. The hig hest levels of SMIT mRNA were observed in the choroid plexus. Intense hybridization signals were found in the pineal gland, the area postrem a, the hippocampus, the locus coeruleus, the suprachiasmatic nucleus, the olfactory bulb and the Purkinje cell and granule cell layers of th e cerebellum. Low to moderate levels of labelling were detected in alm ost all neurones and small glia-like cells throughout the brain. These results suggest that almost all cells in the brain possess an SMIT-me diated osmotic and ionic regulatory system, and uneven densities of po sitive SMIT mRNA signals may reflect the differences in sensitivity of the cells to osmotic and ionic changes and also reflect differences i n permeability of capillaries.