Abstract
Retinal ganglion cells express the voltage-dependent Na+ channel (Nav) in the soma and axon. Electrophysiological studies showed that some amacrine cells generate action potentials in their dendrites and somata. In addition, it is reported that action potentials propagate in dendrites of ganglion cells. Thus, it is important to elucidate localization of Nav within dendrites and somata of amacrine and ganglion cells in the inner plexiform layer (IPL).
We performed immunohistochemistry on the rat retina using antibodies to pan-Nav (K58/35, Sigma). We observed bright dots and thick process-like structures in the IPL, in addition to immunofluorescence of the soma and axon of ganglion cells. Most of the Nav-immunoreactive thick processes (NavIRPs) were short (10-15 μm) and had no apparent branch. Interestingly they had a terminal-like structure at an end with shape of sphere, ring or bifurcation. NavIRPs was comparable in staining intensity to axon bundles of ganglion cells. To examine whether NavIRPs has connection with AII amacrine cells, we performed double immunostaining with parvalbumin (PV-28, Swant), a marker of the AII amacrine cell. The staining indicated that NavIRPs were not parts of AII amacrine cells. The terminal-like structure of some NavIRPs seemed to be close to somata of AII amacrine cells. It is possible that NavIRPs generate action potential and modulate local neural activity in IPL. [Jpn J Physiol 54 Suppl:S163 (2004)]
