Effects of dopamine D(1) receptor blockade on the intensity-response function of ERG b- and d-waves under different conditions of light adaptation

The effect of dopamine D(1) receptor blockade by SCH 23390 on the V-logI function of the ERG b- and d-waves was investigated in dark and light adapted frog eyes. We obtained that the blocker enhanced the amplitude of the b- and d-waves in both conditions of adaptation. The enhancing effect of the blocker was more pronounced on the rod- than cone-dominated responses for the both ERG waves. The absolute sensitivity of the b-wave was not altered, but that of the d-wave was significantly increased. The intensity-response function of the b-wave, but not that of the d-wave, was shifted to the left along the intensity axis. The b-wave V-logI function had steeper slope and narrower dynamic range in both dark and light adapted eyes after the D(1) receptor blockade. The results obtained indicate that the endogenous dopamine, acting through D(1) receptors, does not play a crucial role in the process of retinal adaptation, although it changes in a specific manner the intensity-response function of both the ERG b- and d-waves.