Analysis of two types of cone bipolar cells in the retina of a New World monkey, the marmoset, Callithrix jacchus

Two types of cone bipolar cells, the blue cone bipolar cell and the diffuse bipolar cell (DB3), were labelled immunohistochemically and investigated i n the retina of a New World monkey, the marmoset. Blue cone bipolar cells w ere labelled with an antiserum against cholecystokinin. Short-wavelength-se nsitive (SWS) cones were labelled with an antiserum against the SWS cone op sin. The DB3 cells were labelled with antibodies to calbindin. Blue cone bi polar cells in marmoset do not form a regular mosaic but instead follow the random distribution of the SWS cones. Nevertheless. the SWS cone to blue c one bipolar cell connectivity in marmoset is very similar to that previousl y described for macaque. In contrast to the blue cone bipolar cells! the DB 3 cells form a regular mosaic. The synaptic connectivity of DB3 cells in th e inner plexiform layer was analyzed. They make output synapses onto gangli on cells and amacrine cells, and gap junctions with each other. Our results provide further evidence for the existence of parallel bipolar cell pathwa ys in the primate retina and support the view that the retinae of Old World and New World primates have common neuronal connectivity. The random distr ibution of SWS cones and blue cone bipolar cells is an exception to the gen eral rule of a regular mosaic distribution of cell populations in the retin a.