Voltage-dependent opening of single calcium-activated potassium channels in Helix neurons

Single Ca-activated K channels (C channels) were identified in cell-attached patches in Helix neurons. The respective effects of membrane potential and calcium on the opening probability Po were separated by using Ca-free filled patch electrodes. C channels were found to be highly voltage-dependent, with an e-fold increase in Po per 15 mV increase in potential. The location of the Po(V) curve on the voltage axis was dependent on the intracellular Ca concentration. These data indicate that C channels provide the cell with a powerful repolarizing mechanism.