Insulin-sensitive GLUT4 glucose transporters are colocalized with GLUT3-expressing cells and demonstrate a chemically distinct neuron-specific localization in rat brain

The insulin-sensitive glucose transporter (GLUT) 4, expressed primarily in peripheral tissue, has recently been detected also in the brain, demonstrat ing a region-specific distribution. To identify the chemical nature of neur ons expressing GLUT4 and to disclose whether GLUT4-containing neurons also express the GLUT3 isoform, combined in situ hybridization for GLUT3 mRNA an d double-labeling immunocytochemistry for GLUT4 and different cellular mark ers was performed in brain sections through rat basal forebrain, cerebral c ortex, hippocampus, and cerebellum, In all brain regions examined, GLUT4 im munoreactivity was exclusively found in neurons, and GLUT4-immunoreactive c ells were colocalized with neurons expressing GLUT3 mRNA, In rat basal fore brain, cholinergic and parvalbumin-containing gamma-aminobutyric acid-ergic cells demonstrated GLUT4 immunoreactivity, whereas calretinin-, calbindin- D-, and neuronal nitric oxide synthase-containing neurons did not express G LUT4 protein. Because brain GLUT4 transporters have been suggested to play a role in rapidly providing additional glucose to neurons under conditions of high-energy demand, the selective presence of GLUT4 in basal forebrain c holinergic cells may explain the specific vulnerability of these cells to a lack of glucose supply. (C) 1999 Wiley-Liss, Inc.