Figure 8. ATP-induced I_mVDCC potentiation and inhibition is voltage independent.

In order to evaluate the voltage-dependent properties of I_mVDCC under conditions as similar to the physiological situation as possible, Ba²⁺ was used as the charge carrier. Bath and pipette contained 5 mm Ba²⁺-external and Cs⁺-internal solutions, respectively. A, current-voltage relationships for I_mVDCC in the absence and presence of 100 μm ATP (A) in the bath. B, I_mVDCC activation curve evaluated by tail current analysis and quasi steady-state inactivation curve evaluated by 10 s preconditioning pulses (see Morita et al. 1999). Smooth curves are the best fit of data points (n = 5) by Boltzmann equation: 1/(1 + exp((V_m - V_0.5)/k), where V_m, V_0.5 and k denote membrane potential, half activation or inactivation voltage and slope factor, respectively. C, current-voltage relationships for I_mVDCC in the absence and presence of 1 mm ATP with 41.3 nm protein kinase A inhibitory peptide in the pipette.