Expression of insulin-responsive glucose transporter GLUT4 mRNA in the rat brain and spinal cord: an in situ hybridization study.

Following a previous immunocytochemical study of GLUT4 in the rat brain and spinal cord (J. Comp. Neurol. 399 (1998) 492), we now report the distribution and cellular expression of GLUT4 mRNA in the CNS using reverse transcription-polymerase chain reaction and non-radioactive in situ hybridization (ISH). The former technique demonstrated the expression of GLUT4 in the different regions examined while ISH with a specific riboprobe allowed the anatomical localization of GLUT4 mRNA. A strong hybridization signal was detected in the piriform and entorhinal cortices and in the pyramidal cell layer of the hippocampal CA1-CA3 areas. Numerous moderately labeled cells were additionally observed in the dentate gyrus granular layer, subiculum and most neocortical areas, as well as in different nuclei of the limbic and motor systems. In contrast, positive cell groups were scarce in the hypothalamus. In the hindbrain, a strong expression of GLUT4 mRNA was observed in the large cell bodies of the red nucleus and cerebellar Purkinje cell layer. Moreover, different groups of moderately labeled cells were found in the deep cerebellar and medullary motor nuclei, in various reticular fields and in the ventral horn of the spinal cord. The present results of ISH mostly agree with the immunocytochemical data reported by our group, although the immunoreactive cells were generally less numerous. However, the fact that a high expression of GLUT4 mRNA was observed in cell bodies of the piriform lobe, hippocampus and substantia nigra, whereas the immunoreactivity for GLUT4 was low in these regions, suggests the existence of post-transcriptional regulation of GLUT4 expression which may depend on the physiological conditions of the animals.