Effects of norepinephrine on BAY K-8644-induced contraction in porcine coronary artery.

BAY K-8644 is a dihydropyridine calcium agonist which produces contraction in several isolated vascular preparations--including porcine coronary artery. This study examined the ability of norepinephrine to relax porcine coronary artery previously contracted with BAY K-8644 and compared this to effects on preparations contracted with histamine. Norepinephrine relaxed BAY K-8644 and histamine-treated preparations to approximately base line developed tension. The ED50 value for norepinephrine was the same in the presence of increasing concentrations of either BAY K-8644 or histamine.