Differential effects of dopamine depletion on the distribution of [3H]SCH 23390 and [3H]spiperone binding sites in the goldfish retina

The distributions of dopamine D1 and D2 receptors were studied in intact goldfish retina with in vitro autoradiography. Specific [3H]SCH 23390 binding (D1 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 [3H]spiperone binding (D2 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 [3H]SCH 23390 binding; however, specific [3H]spiperone binding over the OPL and IPL was virtually eliminated, suggestive of D2 autoreceptors on dopamine interplexiform cells. These data are consistent with electrophysiological studies indicating the presence of D1 and D2 receptors in both plexiform layers of the goldfish retina.