Effects of paxilline on K+ channels in rat mesenteric arterial cells

The effects of paxilline, a mycotoxin, on whole-cell outward currents from freshly isolated cells of the rat mesenteric artery were studied. Paxilline inhibited a component of the outward current that was also sensitive to iberiotoxin. Inhibition could be observed at a concentration of 10 nM and complete inhibition of the iberiotoxin-sensitive current was achieved at 300 nM. The inhibition could be described by a single site of interaction with a Ki of 35.7 nM. Paxilline had no effect on the component of the current that was sensitive to 4-aminopyridine. It is concluded that paxilline is a potent inhibitor of large conductance Ca2+ -activated K+ currents in vascular smooth muscle cells.