Differential expression of two distinct vesicular glutamate transporters in the rat retina.

Expression and cellular localization of vesicular glutamate transporters (BNPI and DNPI) were studied in the rat retina. RT-PCR showed expression of both transporter mRNAs. hybridization demonstrated BNPI mRNA signals in the inner segments of photoreceptors and the inner nuclear layer, whereas DNPI mRNA signals were confined to the ganglion cell layer. Punctate BNPI immunoreactivity was localized in the inner and outer plexiform layers, and weak DNPI immunoreactivity was detectable only in some cells and fibers of the ganglion cell layer. The present study suggests that BNPI exists in photoreceptors and bipolar cells, while DNPI is present in ganglion cells, as specific systems in distinct glutamatergic neurons of the retina.