HORIZONTAL CELL CONNECTIONS WITH SHORT-WAVELENGTH-SENSITIVE CONES IN MACAQUE MONKEY RETINA

This study describes the connectivity between horizontal cells and sho rt-wavelength-sensitive (SWS) cones in macaque monkey retina. H1 and H 2 horizontal cells were either labelled with the carbocyanine dye, DiI , or injected intracellularly with Neurobiotin. The retinas were then processed with an antiserum against human SWS cone pigment, which usua lly stained the entire SWS cone. In these double-labelled retinas, the pattern of connectivity of H1 (n = 91) and H2 (n = 7) cells with SWS cones has been determined. About 85% of the H1 cells examined do not c ontact SWS cones. The dendritic terminal knobs of five HI cells that d o contact SWS cones were counted. They have, at most, 3% of their dend ritic terminal knobs at SWS cones. All H2 cells examined make contact with SWS cones. The dendritic terminal knobs of one H2 cell were count ed; about 11% of the dendritic terminal knobs are at the SWS cone. We conclude that horizontal cells in macaque monkey retina show specific patterns of connectivity to SWS cones.