DIFFERENTIAL-EFFECTS OF DOPAMINE DEPLETION ON THE DISTRIBUTION OF [H-3]SCH-23390 AND [H-3]SPIPERONE BINDING-SITES IN THE GOLDFISH RETINA

The distributions of dopamine D-1 and D-2 receptors were studied in intact goldfish retina with in vitro autoradiography. Specific [H-3]SCH 23390 binding (D-1 receptors) was greatest over the outer plexiform layer (OPL)/horizontal cell bodies and less so over the inner nuclear and inner plexiform layers (IPL). Specific [H-3]spiperone binding (D-2 receptors) appeared in two bands, over the OPL/horizontal cell bodies and the IPL. Depletion of retinal dopamine, by intraocular injections of 6-hydroxydopamine, had no effect on the pattern and density of [H-3]SCH 23390 binding; however, specific [H-3]spiperone binding over the OPL and IPL was virtually eliminated, suggestive of D-2 autoreceptors on dopamine interplexiform cells. These data are consistent with electrophysiological studies indicating the presence of D-1 and D-2 receptors in both plexiform layers of the goldfish retina.