Stimulation of endogenous dopamine release and metabolism in amphibian retina by light- and K+-evoked depolarization.

The release and metabolism of dopamine (DA) in retina was assessed using an in vitro eye cup preparation of the African clawed frog. The concentration of DA in the incubation medium and of 3,4-dihydroxyphenylacetic acid (DOPAC) and DA in retinas was measured by high-performance liquid chromatography with electrochemical detection (HPLC-ED). K+-induced depolarization stimulated DA overflow from the eye cups into the incubation medium and increased tissue DOPAC levels in dark-adapted retinas. Basal and K+-stimulated DA overflow and DOPAC accumulation were Ca2+-dependent. Exposure of dark-adapted retinas to constant white light for 1 h also increased DA overflow and DOPAC levels, while 1 h of alternating 10 s periods of light and dark had no effect. The results indicate that DA release and metabolism may be stimulated as a function of light-adaptation.