IMMUNOCYTOCHEMICAL LOCALIZATION OF DOPAMINE D-1 RECEPTORS IN THE RETINA OF MAMMALS

Dopamine is one of the major neurotransmitters in the retina. It is re leased from amacrine and interplexiform cells into both inner (IPL) an d outer (OPL) plexiform layers. Several dopaminergic actions are known to occur through D-1 receptors (D1R) but the precise location of thes e receptors has not been established. An antibody that recognizes the intracytoplasmic C-terminal of the rat D1R was used to detect D1R, imm unohistochemically, in rats (Wistar and RCS), mouse, hamster, and maca que monkey retinas. The OPL was heavily stained in each species, consi stent with the known actions of dopamine on horizontal cells. Three to five bands were observed in the IPL, depending on species. Three were in the a sublayer, the outermost of which was close to the amacrine c ell layer, and may represent the massive dopamine input to the An rod- amacrine cells. As observed in mice, where bipolar cells are D-1-immun oreactive, the band located in sublayer 3 of the IPL may contain cone- bipolar cell terminals. A band of D1R-immunoreactivity in the b sublay er of the IPL contains ON-bipolar cell terminals and a second site of interaction between dopaminergic cells and the AII amacrine cells. Thi s sublayer was absent from the RCS rat retina, suggesting a severe imp airment of the rod-driven pathway following rod degeneration in these mutant rats. Cells in the ganglion cell layer exhibited relatively hea vy staining, and may be ganglion cells or displaced amacrine cells. So me extrasynaptic localizations of D1R in the retina are suggested.