Abstract
Retinal ganglion cells and subsets of retinal amacrine cells generate TTX-sensitive action potentials evoked by light stimulus. It has been reported that voltage-dependent sodium channel (Nav) α subunits, Nav1.1, Nav1.2, Nav1.3, and Nav1.6, are expressed in the retinal ganglion cells (Fjell J et al., Mol Brain Res 50:197-204, 1997; Boiko T et al., J Neurosci 23:2306-2313, 2003). However, subtypes of Nav expressed in retinal amacrine cells have not been identified. To examine the specific Nav subtypes expressed in the retinal amacrine cells, we applied in situ hybridization on the rat retina with the RNA probes that recognize Nav1.1, Nav1.2, Nav1.3, and Nav1.6. We found that Nav1.2, Nav1.3, and Nav1.6 were localized in the ganglion cell layer (GCL). 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 border between INL and the inner plexiform layer. It is probable that these cells are subsets of amacrine cells. Difference in expression pattern of Nav might reflex functional difference of action potentials between amacrine and ganglion cells. [J Physiol Sci. 2006;56 Suppl:S175]
