EFFECTS OF POTASSIUM CHANNEL OPENERS ON NA+ AND K+ CURRENTS IN RABBITSINUS NODE AND ATRIAL MYOCYTES

The effects of the potassium channel openers (KCOs) Cromakalim and Lem akalim on rabbit sinoatrial and atrial myocytes were examined by means of the whole-cell patch-clamp technique. Lemakalim(up to 100 mu M) ha d no effect on potassium current in sinoatrial cells. Both Lemakalim a nd Cromakalim (100 mu M) displayed a two-fold action on atrial myocyte s: (1) they increased an outwardly rectifying conductance at potential s positive to E(K) and, (2) they markedly decreased a TTX-sensitive Na + current active in the voltage range -50/-30 mV. This novel action on TTX-sensitive currents is of particular interest since these two benz opyrans have been thought to specifically target potassium channels.