Light activation of dopaminergic neurons in rat retina is mediated through photoreceptors

The effect of light on retinal dopamine turnover was studied in the RCS mutant strain of rats with inherited retinal dystrophy and in age-matched controls. Retinal dopamine and DOPAC were decreased in the 60-day-old RCS rats with complete photoreceptor degeneration killed in the light phase of the light-dark cycle. After 24 h dark adaptation, exposure to light markedly increased retinal DOPAC and dopamine in controls but had no effect in 70-day-old RCS dystrophic animals. Findings indicate that light activates retinal dopaminergic neurons via photoreceptor stimulation and not directly.