IMMUNOCYTOCHEMICAL ANALYSIS OF BIPOLAR CELLS IN THE MACAQUE MONKEY RETINA

Transfer of visual information from photoreceptors to ganglion cells w ithin the retina is mediated by specialized groups of bipolar cells. A t least 10 different morphological types of bipolar cells have been di stinguished in Golgi studies of primate retina. In the present study, bipolar cell populations in the macaque monkey retina were identified by their differential immunoreactivity to a spectrum of antibody marke rs. This enabled their spatial density and photoreceptor connections t o be analysed. An antibody against the beta isozyme of protein kinase C (PKCA(beta)) labelled many cone bipolar cells. Invaginating (presume d ON) cone bipolar cells and rod bipolar cells were prefentially label led with a monoclonal antibody raised against rabbit olfactory bulb. F lat (presumed OFF) bipolar cells were labelled with an antiserum again st the glutamate transporter protein (GLT-1). Different populations of diffuse cone bipolar cells, which contact 5-10 cones, could be distin guished. The GLT-1 antiserum preferentially labelled the flat diffuse bipolar cell type DB2 (Boycott and Wassle, 1991, fur. J. Neurosci. 3:1 069-1088) as well as flat midget bipolar cells. Antibodies to calbindi n (CaBP D-28K) labelled the flat diffuse bipolar cell type DB3 and (po ssibly) the invaginating diffuse bipolar cell type DB5. An antibody ag ainst the cr, isozyme of PKC labelled an invaginating diffuse bipolar cell type (DB4) as well as rod bipolar cells. Comparison of the spatia l density of cone bipolar cell populations with that of photoreceptors suggests that each bipolar cell class provides a complete coverage of the cone array (each cone is contacted by at least one member of ever y bipolar cell class). These results support the classification scheme of Boycott and Wassle (1991) by showing that different diffuse bipola r cell classes express different patterns of immunoreactivity, and the y reinforce the view that different spatial and temporal components of the signal from the photoreceptor array are processed in parallel wit hin the primate retina. (C) 1994 Wiley-Liss, Inc.