Figure 2.

Activation, inactivation, and recovery from inactivation of I_A current. (A) A double test voltage step was applied in the control and in catechol (100 μM), the first to V_t between −60 and +30 mV and the second to +30 mV. I_A current was isolated by subtracting the current evoked in catechol from that evoked in control. (B) The activation curve (■) was fitted with the best-fitting Boltzmann equation: G/G_max = (1 + e^{(V − V1/2)/k})⁻¹. The steady-state inactivation curve (○) was determined by plotting the mean normalized conductance as a function of the membrane potential. (C) A two-voltage-step protocol to +30 mV applied at increasing intervals was used to determine the recovery from inactivation of the I_A current. The traces shown correspond to the current blocked by catechol. (D) The recovery from the inactivation curve corresponds to the mean normalized I_A current amplitude as a function of the interpulse duration.