Effects of Bay K 8644 on the electrically evoked and KCl-evoked norepinephrine release and the corresponding contraction in isolated canine saphenous veins.

Bay K 8644 caused no significant effects on the 3H overflow and contraction evoked by electrical stimulation in the canine saphenous vein preloaded with [3H]norepinephrine. Bay K 8644 significantly enhanced the 3H overflow evoked by 40 mM KCl in a concentration-dependent manner, which was antagonized by nisoldipine. Bay K 8644 failed to significantly augment the KCl-evoked contraction. These results suggest that there is a difference between the modes of action of Bay K 8644 on norepinephrine releases evoked by electrical stimulation and KCl.