ANTAGONIZING ACTION OF CHLORPROMAZINE, DIBENAMINE, AND PHENOXYBENZAMINE ON POTASSIUM-INDUCED CONTRACTION

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Abstract
When rabbit aortic strips were incubated for 1 hr in Ringer''s solution containing 10-5 [image] chlorpromazine, 10-4 [image] Dibenamine, or 10-4 [image] phenaxy-benzamine, or 2 hr in Ca-free Ringer''s solution, they failed to respond to high K (10-80 m[image]). With increasing external Ca this inhibitory action on the K-induced contraction decreased. Incubation in solutions containing 10-4 [image] phentolamine, dihydroergotamine, vohimbine, azape-tine, pronethanol, dichloroisoproterenol, or MJ 1998 [3-(l-hydraxy-2-methylaminopropyl) methane sulfonanilide hydrochloride] did not inhibit the response to K. The responses to angiotensin (5 x 10-7 [image]) were not antagonized by any of the blocking agents. The 3 agents blocking the K-induced contraction inhibited Ca-45 uptake during these contractions; however, they did not inhibit Ca-45 uptake of unstimulated muscle. The other agents tested failed to decrease the calcium-45 influx during K contraction. There were no tissue electrolyte changes found after treatment of the aortas with any of the agents. The results suggest that the inhibition observed was mediated by a decrease in Ca movement rather than a decrease in K movement into the intracellular space.