Figure 5. Treatments (•) with dopamine (A), SKF 38393 (a dopamine D1 receptor agonist, B) or quinpirole (a dopamine D2 receptor agonist, C) on voltage-activated Ca²⁺ current in isolated RGCs.

Dopamine or SKF 38393 decreased the Ca²⁺ current, whereas quinpirole produced no effect. After 3 min of washout (□), the current returned to levels as measured in normal bath solutions (○). Traces under each current–voltage curve show the Ca²⁺ current recorded in normal bath solutions (top), in drug solutions (middle) and after 3 min of washout (bottom). Testing potential, +10 mV; holding potential, −90 mV.