Abstract
Immature cerebellar granule cells (CGCs) express GABAA receptors in the external granular layer (EGL).However its function has not still been well understood.Evaluation of spatio-temporal distribution of GABA in the developing cerebellum, serve us to clarify the role of GABAA receptors in EGL.To this end, we have developed the novel method to image the extracellular GABA in acute slices with an enzyme-linked assay system using GABase, which catabolize with simultaneous production of NADPH. This imaging enables us to examine the distribution of extracellular GABA.Intense NADPH fluorescence was observed in the upper part of EGL at P3, whereas it was restricted around the GABAergic Purkinje cells at P8.Whole cell patch-clamp recordings from CGCs in EGL confirmed that CGCs could tonically respond to the extracellular GABA.To evaluate the mechanism of increases in extracellular GABA in EGL, we examined the expression pattern the vesicular GABA transporter (VGAT), which is involved in vesicular GABA release, by immnohistochemistry. We found that VGAT was expressed on Bergman glial fibers in EGL at P3.Taken together, our results suggest that the temporal release in extracellular GABA in EGL, it might be regulated by VGAT. [J Physiol Sci. 2008;58 Suppl:S199]
