Cd2+ regulation of the hyperpolarization-activated current IAB in crayfish muscle (original) (raw)

The effects of Cd2+ on the hyperpolarization-activated K(+)-mediated current called IAB (Araque, A., and W. Buño. 1994. Journal of Neuroscience. 14:399-408.) were studied under two-electrode voltage-clamp in opener muscle fibers of the crayfish Procambarus clarkii. IAB was reversibly reduced by extracellular Cd2+ in a concentration-dependent manner, obeying the Hill equation with IC50 = 0.452 +/- 0.045 mM and a Hill coefficient of 1 (determined from the maximal chord conductance of IAB). Cd2+ decreased the IAB conductance (GAB) and shifted its voltage dependence towards hyperpolarized potentials in a similar degree, without affecting the slope of the voltage dependence. The IAB activation time constant increased, whereas the IAB deactivation time constant was not modified by Cd2+. The IAB equilibrium potential (EAB) was unmodified by Cd2+, indicating that the selective permeability of IAB channels was not altered. IAB was unaffected by intracellular Cd2+. The Cd(2+)-regulation of IA...