THE EFFECT OF DOPAMINE ON THE RESPONSE TO PATTERN STIMULATION - STUDYOF THE CHICK ERG

The effect of dopamine (DA) on the chick ERG was studied to evaluate i ts action on the on and off pathways and on the contrast mechanism wit h regard to background intensity. After intravitreal injection of DA, the b-wave, one component of the on response, was reduced with stimulu s intensities lower than background intensity and enhanced with stimul us intensities that were higher. While the d-wave, one of the off resp onses, was enhanced with stimulus intensities higher than background i ntensity but not reduced with stimulus intensities that were lower. Th e pattern ERG amplitude was decreased at higher spatial frequencies. T hese results suggest that DA has different effects on the on and the o ff pathways as a function of the adaptive state and could affect the c ontrast mechanism.