The Journal of comparative neurology
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The I1 dopaminergic interplexiform cells of the fish retina are believed to modulate horizontal cell coupling by increasing gap junction resistance. Dopamine also modulates the morphology of horizontal cell gap junctions and mimics the effects of light adaptation. To determine whether the light-dependent changes in gap junction morphology are due to endogenous dopamine release, horizontal cell gap junctions were studied in goldfish retinas lacking dopaminergic neurons. ⋯ These results demonstrate that high soma gap junction particle densities can be correlated with the absence of dopamine and low densities associated with the presence of dopamine. The differences in gap junction particle density between lesioned and lesioned + dopamine-treatment were similar to differences between nonlesioned dark-adapted (1 hour) and light-adapted retinas, respectively. Therefore, the particle density of light- and dark-adapted soma gap junctions suggests a greater release of dopamine in light-adapted fish than in 1 hour dark-adapted fish.(ABSTRACT TRUNCATED AT 250 WORDS)