Objective: 

Dopamine is the predominant catecholamine in the vertebrate retina, acting through five subtypes of dopamine receptors. It is supposed that dopamine may be related to the process of retinal adaptation. The aim of this study was to investigate the possible contribution of D1 dopamine receptors to retinal sensitivity control under different conditions of adaptation.

Methods: 

The effect of dopamine D1 receptor blockade by SCH 23390 on the intensity-response function of the ERG ON and OFF response was investigated in dark and light adapted frog eyes.

Results: 

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 relatively 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 - log I function had steeper slope and narrower dynamic range in both dark and light adapted eyes after the D1 receptor blockade. The latency of the responses was not altered, but the implicit time of the rod-dominated responses was significantly increased.

Conclusions: 

The results obtained indicate that the endogenous dopamine, acting through D1 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.