Figure 1.

Properties and distribution of I_h in Purkinje cells. A1, I_h recorded in a dendritic cell-attached patch-clamp recording 93 μm from the soma. The patch was held at −52 mV and hyperpolarized for 1 s in steps of 10 mV from −52 to −142 mV. Tail currents evoked by stepping back to −52 mV for 200 ms are expanded. A2, Activation curve of the I_h current in A1. The peak tail currents (*) are normalized to the top plateau of a Boltzmann function. The solid line represents a sigmoidal fit to the data points giving a midpoint of activation at −91.1 mV with a slope constant of −9.1 mV (sigmoidal fit to the mean ± SEM of 5 recordings: V_1/2 = −90.3 mV, slope constant = −9.7 mV). A3, Time constants of I_h activation and deactivation. The time constants were obtained by fitting single exponentials to traces in which the I_h current is activated from the closed state or deactivated from a maximally open state at potentials between −142 and −82 mV (open) and between −72 and −52 mV (filled), respectively (n = 5). B, Distribution of I_h along the soma–dendritic axis. The steady-state I_h amplitudes from full activation of the current at −142 mV (inset, arrow) are plotted as a function of distance from the soma (n = 53 cell-attached patches). A straight line with a slope of −3 pA/100 μm is fitted to the data points.