Blue cone bipolar cells of the macaque retina

Abstract

Antisera which recognize glycine-extended precursors of the peptide chole-cystokin in labeled neurons in the macaque retina with dendrites that ran obliquely and had diffuse dendritic terminals as is the case for blue cone bipolar cells described previously. They clearly formed a single population since the density and sizes of their perikarya varied monotonically with eccentricity, while the levels of their perikarya and axon terminals were constant. Short-wavelength cones were also labeled in some preparations, either with Procion Black or anti-blue opsin, and the labeled bipolar cells received input exclusively from these cones. The dendrites formed the central elements at ribbon synapses in the short-wavelength cones, and the axons of the labeled bipolar cells branched in the fifth stratum of the inner plexiform layer. Taken together, these findings indicate that the labeled bipolar cells were different from the invaginating midget bipolar cells that contact middle- and long-wavelength cones and suggest that the labeled bipolar cells depolarize in response to increments in short-wavelength stimuli. There were numerous, unlabeled bipolar cell dendrites receiving inputs from short-wavelength cones at other types of contacts, however, and these presumably belonged to bipolar cells with hyperpolarizing light responses.