Contribution of the IK in the synaptic transmission between the rod bipolar and AII amacrine cells. (A) Rod bipolar cells were stimulated by 65 pA injection in the current-clamp mode and synaptic currents were recorded in the AII amacrine cells with −70 mV-holding potential. By the clotrimazole application, repolarization was reduced, and synaptic current was elongated in the AII amacrine cells. (B-E) Analysis of the synaptic currents in the AII amacrine cells. We measured the onset time (C), peak amplitudes (D), decay time (from peak to baseline, E), and area under curve (AUC, F) of the synaptic current recorded in AII amacrine cells. The rising time, decay time, and AUC were statistically significantly increased by clotrimazole treatment, and the rising time was decreased by clotrimazole (Student’s t-test, n = 10, P < 0.05). (F) Rod bipolar cells were stimulated by 25 pA injection in the current-clamp mode, and synaptic currents were recorded in the AII amacrine cells with a −70 mV holding potential. By the clotrimazole application, the double peak of the membrane potential was recorded in the rod bipolar cells (arrow) but not in control. The synaptic current of the AII amacrine cells showed weak evocation of the second synaptic current during the decay process of the primary synaptic current (green arrow) by clotrimazole, and the second event was synchronized with the second peak of the rod bipolar cell membrane potential. (G) The average number of the “additional peak” of the rod bipolar cells (Total additional peak/Total rod bipolar cell number). An additional peak after the initial peak was rare in the control, while an average of one additional peak was detected by clotrimazole-treated rod bipolar cells (n = 8 for control, n = 10 for clotrimazole group). (H) The probability of the re-opening of the Ca²⁺ channel (double peak) in the rod bipolar cells (double peak rod bipolar cell/total rod bipolar cell, left) and the re-release of the synaptic currents in the AII amacrine cell (a number of second event in AII amacrine cell/double peak rod bipolar cell). Only 20% of the control rod bipolar cells (black) exhibited re-activation, while clotrimazole-treated cells showed 80% of the re-activation (left). And, among the pairs of the re-activated rod bipolar cell and AII amacrine cells, 40% of the AII amacrine cells showed re-evoke of the synaptic currents, synchronized with re-activation of the rod bipolar cells (n = 8 for control, n = 10 for clotrimazole group).