Characterization and isolation of mammalian retinal neurons.

In mammalian retina the following groups of neurons are to be found: ganglion, amacrine, horizontal, bipolar, photoreceptor and interplexiform cells. Within each class of cells there is a great deal of heterogeneity, which Ramon y Cajal had recognized as far back as 1893. Initial morphological studies, later substantiated by the electrophysiologists, proved beyond doubt that there are subdivisions within each class of neuron. For example, within the cat retina at least three different types of ganglion cells (Boycott & Wassle, 1974). five different types of bipolar cells (McGuire et al., 1980) and 12 types of amacrine cells (Cajal, 1893) have been described. The subdivision of neuronal groups within the amacrine cells, in particular. has been extensively studied in recent years because of the introduction of immunohistochemical procedures to localize neurotransmitter-like substances (Osborne, 1982; Stell et al., 198 1). Most retinal neurons (e.g. ganglion cells), except certain amacrine cells, do not strain positively for the battery of immunohistochemical procedures at present available to localize known neurotransmitter substances. One major finding from recent immunohistochemical studies is that no correlation exists