Modification of electroretinograms in dopamine-depleted retinas.

The functional role of dopamine in frog retina was examined in a combined neurochemical, immunohistochemical and electrophysiological study. Dopamine and serotonin are the primary monoamines present in the retina and they are localized to amacrine cells which have distinct morphologies. Intravitreal injection of 6-hydroxydopamine was found to produce a selective depletion of retinal dopamine content and elimination of tyrosine hydroxylase-like immunoreactivity. Electroretinograms from 6-hydroxydopamine-treated retinas demonstrated enhanced oscillatory potentials and a lengthening of the b-wave implicit time compared to vehicle control retinas; both of these changes in the electroretinogram were reversed by the dopamine agonist apomorphine. These observations support earlier suggestions that dopamine-containing amacrine cells are part of a retinal feedback system that generates oscillatory potentials and plays a role in light adaptation.