Fig. 4

Changes in horizontal cell (HC) membrane potential alter the amplitude and voltage dependence of I _Ca in an adjacent cone simultaneously recorded: these effects are blocked by application of HEPES. A I _Ca of cone in tiger salamander retinal slice was recorded under the whole-cell voltage clamp condition with a ramp-function from −90 to +60 mV (0.5 mV/ms) applied from a steady holding potential of −70 mV. By step-wise depolarization of HC simultaneously voltage-clamping at −90, −70, −40 and 0 mV, the cone I _Ca was progressively decreased in amplitude and positively shifted in the activation voltage to more positive potentials. B Addition of HEPES (10 mM) abolished the voltage shift and amplitude changes of cone I _Ca curves produced by the HC polarization (from Cadetti and Thoreson [55])