Figure 4.

Dopamine D₁ receptors mediated the effects of light adaptation on voltage-gated sodium currents. A, A dopamine agonist, ADTN (20 μm), reduced the sodium currents in dim conditions (n = 5) compared with control current in dim light (dotted line, same as Fig. 3A, top). B, A D₁ receptor blocker, SCH23390 (SCH; 50 μm), blocked the ADTN effect (n = 3). The dotted line is control current in dim light from Figure 3A (top). C, Bright illumination did not reduce the sodium current when D₁ receptors were blocked (50 μm SCH23390; n = 3). The dotted line is the control current in bright conditions from Figure 3A (bottom). D, E, Effects of agonists and antagonists on peak amplitude (D) and charge transfer (E). *Significant differences from control (p < 0.05); ^#significant differences from ADTN (dim; p < 0.05).