The cGMP-gated channel of rod outer segments is not localized in bipolar cells of the mammalian retina.

It has recently been suggested (Nature, 346 (1990) 269-271) that ON-bipolar cells express the same biochemical cascade and guanosine 3',5'-cyclic monophosphate (cGMP)-gated cation channel as rod outer segments. An antibody directed against the cGMP-gated channel of bovine rod outer segments was applied to cryostat sections of rat and cat retinae. No immunocytochemical labelling was found in bipolar cells. Therefore, if those cells express a cGMP-gated channel, it must be immunologically different to the 63 kDa protein constituting the cGMP-gated channel of the outer segment.