Voltage-dependent sodium channel alpha subunit immunoreactivity is expressed by distinct cell types of the cat and monkey retina

Document Type

Journal Article

Publication Date



Visual Neuroscience








Bipolar cells; Cones; Ganglion cells; Horizontal cells; Immunohistochemistry


Polyclonal (7493 and 7317) and monoclonal (mAb3) antibodies, generated to the a subunit of the voltage-gated sodium channel (aNaCh), were employed to assess the cell types containing aNaCh-like immunoreactivity in the mature cat and monkey retina. Immunoblot analyses of retinal proteins in the cat revealed that the polyclonal and monoclonal antibodies we employed labeled a band in the 260-kDa region which corresponds to the molecular mass of the a subunit of the NaCh. In both the cat and monkey, these antibodies immunolabeled several distinct types of retinal cells. With the polyclonal antibodies immunoreactivity was observed in ganglion cells and their intraretinal axons, in horizontal cells, and unexpectedly, in cones. In addition, in both species, a limited number of heavily labeled profiles, presumed to be bipolar cells, were seen in the inner nuclear layer. In cat and monkey the monoclonal antibody labeled axons in the fiber layer, ganglion cell somata, and a continuous band of immunoreactive cell bodies (presumed bipolar cells) situated in the outer half of the inner nuclear layer. By immunolabeling isolated cells dissociated from the cat retina, it was possible to demonstrate unequivocally that a population of bipolar cells was labeled by the monoclonal and the polyclonal antibodies we employed. The differences in the labeling observed with the monoclonal antibody as compared to the polyclonal antibodies were interpreted as reflecting the presence of different a-subunit subtypes in the mammalian retina. Collectively, our findings suggest that aNaCh-Iike proteins are expressed by a more diverse population of retinal cells than expected on the basis of previous physiological and immunohistochemical studies. © 1994, Cambridge University Press. All rights reserved.

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