抄録
In the retinal ganglion cells (RGC), various types of voltage-gated sodium channel (Nav) α subunit mRNAs (Nav1.1, Nav1.2, Nav1.3, and Nav1.6) are expressed (Fjell et al., Mol Brain Res 50:197-204, 1997). Like RGC, subsets of retinal amacrine cells generate TTX-sensitive action potentials evoked by light stimulus, but subtypes of Nav expressed in these cells have not been identified. To examine the specific Nav subtypes expressed in the retinal amacrine cells, we applied in situ hybridization (ISH) on the rat retina with the RNA probes that recognize TTX-sensitive Nav (Nav1.1, Nav1.2, Nav1.3, Nav1.6 and Nav1.7). We found that Nav1.2, Nav1.3, and Nav1.6 were localized in the ganglion cell layer (GCL). Nav1.7 showed weak and widespread expression in the retina. Interestingly, Nav1.1 was expressed not only in GCL, but also in the inner nuclear layer (INL). Cell bodies of Nav1.1-positive cells in INL were located on the INL/IPL (inner plexiform layer) border. Cell bodies of the AII amacrine cells are located close to INL/IPL border, and these cells can be labeled with antibodies to parvalbumin (PV). Therefore, we tried to combine ISH technique with immunohistochemistry. In most of Nav1.1-positive cells located on the INL/IPL border, PV-immunoreactivity was observed. Our results suggest that at least Nav1.1 is expressed in AII amacrine cells, while various types of Nav are expressed in RGC. This difference in expression pattern might reflex functional difference of action potentials between these two types of cells. [J Physiol Sci. 2007;57 Suppl:S104]
