The effects of tetraethylammonium ions, 4-aminopyridine or quinidine on K+-currents in single smooth muscle cells of the rabbit portal vein.

Whole-cell and isolated patch configurations of the patch clamp technique were used to distinguish K+-channels by their pharmacological characteristics in single, enzymatically dispersed, smooth muscle cells from the rabbit portal vein. Results suggest that spontaneous transient outward currents are carried mainly by large conductance Ca2+-activated K+-channels and outward current evoked by depolarization of the membrane is carried partially by these channels but also by a time- and potential-dependent K+-channel blocked by 4-aminopyridine.