Figure 3.

Heterogeneous whole-cell currents from type I cells in the third postnatal week are consistent with more than one negatively activating conductance. Currents from a P17 (A) and a P15 (B) cell. Scale bars in A apply to B. Traces on the right show tail currents on an expanded time scale (20 ms). C, Activation curves generated from tail currents (A, B, insets) and additional traces. Tail potentials, −59 mV (A) and −39 mV (B). The P15 cell (B) had a broader activation range that was better fit with the sum of two Boltzmann functions (Eq. 2) than with a single Boltzmann function (Eq. 1). Fit parameters are as follows: A (single Boltzmann function, shown), V_1/2 of −87 mV, S of 5.3 mV; B (single Boltzmann function, not shown) V_1/2 of −75 mV, S of 11.6 mV; B (double Boltzmann, shown), V₁ of −83 mV, S₁ of 6.0 mV, fractional amplitude (A₁) of 0.65; V₂ of −60 mV, S₂ of 4.0 mV, A₂ of 0.35.