Modification of Calcium-Activated Chloride Currents in Cerebellar Purkinje Neurons.

The whole-cell voltage clamp technique was employed to record the total ionic currents in rat cerebellar Purkinje neurons. When intrapipette solution contained 120 mM KCl, replacement of the standard external physiological saline with Na-free solution resulted in appearance of inward tail current after the end of the depolarizing pulse. When intrapipette potassium ions were replaced for cesium ones, the tail currents were observed even in the presence of normal Na+ concentration (140 mM) in the external solution. Tail currents were not observed when external solution contained no Cl- and/or Ca2+ ions. Niflumic acid (25-100 μM) blocked these currents by 80-100%. Complete replacement of external Na+ for Tris ions pronouncedly augmented the amplitude and duration of the tail currents. These findings suggest that the tail transients in rat cerebellar Purkinje neurons are calcium-activated chloride currents whose amplitude and kinetics depend on ionic composition of the extracellular and intracellular solutions.