Figure 4. v‐ATPase inhibitor, bafilomycin (BAF), prevents the loading of protons into synaptic vesicles but did not eliminate feedback .

A, I _Ca recorded from a cone in control solution (black) and from another cone in the presence of 3.5 μm BAF (grey). I _Ca was evoked by a voltage step from −70 to −10 mV for 100 ms. Passive currents were subtracted by a P/8 protocol. BAF treatment increased the initial portion of I _Ca relative to control, showing loss of proton inhibition. B, differences in the inhibition of the initial portion of I _Ca were statistically significant by two different measures: (1) comparing the amplitude of I _Ca measured 20 and 90 ms after initiation of the step (I _20ms/I _90ms; n = 6; unpaired t‐test, P < 0.00001) and (2) comparing the total charge transfer (Q _Ca) that entered the cone during the first 25 ms (grey‐shaded region; n = 6; unpaired t‐test, P < 0.00002). C and D, application of BAF (triangles) for 15–60 min produced no statistically significant effects on feedback assessed by changes in the peak amplitude of I _Ca (C) and V ₅₀ (D) that were induced by changes in HC holding potential (n = 7) when compared to control pairs (n = 28; unpaired t‐tests). E and F, effects of BAF (triangles) on feedback assessed by changes in V ₅₀ (E) or peak amplitude of I _Ca (F) were also not statistically significant in retinas treated for at least 12 h with BAF plus 1% BSA (n = 5) relative to control tissue incubated overnight in 1% BSA without BAF (n = 4). [Colour figure can be viewed at wileyonlinelibrary.com]