Figure 4. Effects of SKF83959 on the kinetic properties of Ih current.

A. the activation curves of Ih plotted in control and in the presence of SKF83959 (50 µM). The neurons were held at −20 mV. Ih currents were elicited with 1.5-sec hyperpolarizing steps to various potentials followed by a voltage step to −80 mV to measure the tail currents. Normalized amplitude of the tail current was plotted as the function of the test potentials and fitted with the Boltzmann equation: I/Imax = 1/[1+exp(V-V1/2)/s], where I/Imax is the normalized amplitude of the tail current, V is the test potential, V1/2 is the half-activation potential, and s is the slope factor. B. Plot of the activation time constant (τf) of Ih against the test potentials. The trace of Ih current was fitted with bi-exponential functions. n = 6 for each symbol. *P<0.05, **P<0.01 vs. Control.