Figure 5. Potentiation of flash responses by dim background light occurs with weak Ca²⁺ buffering.

Whole-cell voltage clamp recording from an ‘on’ bipolar cell equilibrated with a patch-pipette solution containing 1 μM free Ca²⁺ buffered with 5 mm BAPTA instead of N,N,N‘,N‘-tetrakis(2-pyridyl-methyl)ethylenediamine (TPEN). The flash intensity ranged from 0.0625 to 16 Rh**, with the dimmest range (0.0625-0.5 Rh**) marked by the diamonds above the trace. The zero-current level is marked by the dashed lines at the beginning of the record, and the cell was clamped to its dark potential of -43 mV.