[Blocking calcium-dependent potassium in permeability of skeletal muscle fibers in the frog by a sodium-free medium].

In voltage-clamped frog muscle fibres, the total or partial substitution of NaCl by LiCl does not alter the calcium-dependent slow outward potassium current. In contrast, an equimolar substitution of NaCl by choline-Cl (+atropine) or trisCl induces a rapid and reversible blockage of the current.