Figure 1.

General properties. (A–C) Representative currents obtained in response to hyperpolarizing pulses in 32.5 mM external K⁺ solution: (A) EC1 saline with 1 mM kynurenic acid, 10 μM bicuculline (BL1 mix), 0.6 μM TTX, 100 μM Cd²⁺; (B) same solution as in A plus 10 μM ivabradine; (C) same solution as in B plus 2 mM Ba²⁺. Voltage steps from a holding potential of −40 mV with hyperpolarizing steps ranging from −60 to −130 mV in 10 mV increments. (D): I–V relationship of peak (green dots) and steady-state (blue dots) current; mean current amplitude of 81 cell recordings. Vertical error bars represent standard error; EC2 saline, with BL1 and BL2 mixes of blockers. (E) Instantaneous I/V curve during application of a 220 mV/s ramp protocol (from −180 to +40 mV, 0.23 V/s) in a DA PG cell perfused with the solution described in (A), after subtraction of the ohmic leak; the red dot (−41.3 mV) marks the observed reversal potential, the green dot the Nernstian equilibrium potential in the experimental conditions used ([K⁺]_o = 32.5 mM). All the experiments shown in this figure were performed in slice, perforated patch configuration, at 34°C.