キンギョおよびサル網膜におけるV-ATPaseの組織化学的局在: 水平細胞から錐体視細胞へのプロトンフィードバック仮説を支持する根拠

抄録

It has been hypothesized that proton mediates the negative feedback from horizontal cells (HCs) to cone photoreceptors, and the proton-mediated feedback is responsible for forming antagonistic center-surround receptive field in the outer retina. We have shown that bafilomycin A1, a specific inhibitor of V-ATPase (H⁺ pump), suppressed depolarization-induced acidification of the external surface of isolated HCs, suggesting the existence of V-ATPase in the HC membrane of goldfish retina. We studied the localization of V-ATPase by immunohistochemical analyses of the fish and monkey retinal slice by using an antibody against V-ATPase under the fluorescence microscopy and the immuno-electron microscopy. In the fish retina a very strong immunoreactivity (IR) was seen at the cone terminals. IR was also observed in the membrane of external HCs. IR was seen in the outer plexiform layer where HC dendrites invaginate into the photoreceptor cell terminals. In the invaginating synapse, IR was located at the tips of HC dendrites. In the monkey retina the V-ATPase IR was seen also in HCs. These results suggest that HC dendrite is the active site of proton extrusion. [J Physiol Sci. 2008;58 Suppl:S174]