Postnatal Development of the Light Response of the Dopaminergic Neurons in the Rat Retina

Abstract: The effect of light on retinal dopamine (DA) synthesis and content in dark‐adapted rats was assessed 15 h and 2, 4, 7, and 16 days after eye opening (13 to 14 days after birth). The accumulation of dihy‐droxyphenylalanine (DOPA) following inhibition of its decarboxylation was used to estimate DA synthesis. At 7 and 16 days, but not earlier, light significantly augmented DOPA formation. These increases were as dramatic as those reported for adult rats. DA in dark‐adapted retinas ranged from 0 (undetectable) at 15 h to 83% of adult levels at 16 days, but were only 36% of that of adult retinas at 7 days. Light produced a significant decline in DA at 16 days but not at any other time point. These results indicate that the dopaminergic neurons synthesize transmitter and respond to light at a time when the neuronal pools of DA are not yet mature.