DISTRIBUTION AND CHARACTERIZATION OF THE ADRENOCEPTORS IN DOG CORONARY-ARTERIES

  • 1 January 1979
    • journal article
    • research article
    • Vol. 239  (2) , 195-207
Abstract
Effects of catecholamines were studied in vitro on different portions of the left coronary artery of the dog. Adrenaline [epinephrine, E], noradrenaline [norepinephrine, NA] and isoprenaline [Isop] produced dose-related contractions in the common portion of the coronary artery which were blocked by phenoxybenzamine. The proximal portions were relaxed by NA and Isop, but contracted or relaxed by E following an initial transient contraction. The contraction was blocked by phenoxybenzamine and the relaxation was blocked by propranolol. E, NA and Isop caused only relaxations which were blocked by propranolol in the distal portion and in the small branches. In coronary, femoral and tracheal strips contracted previously by KCl with or without a phenoxybenzamine pretreatment, Isop produced dose-dependent relaxations. The dose-response curves for Isop were shifted to the right on treatment with practolol. The blocking effects of practolol were nearly 10 times more potent in the coronary artery in comparison with the femoral artery and the trachea. Apparently the common portion mainly possesses .alpha.-adrenoceptors, the proximal portion contains both .alpha.- and .beta.-adrenoceptors, and .beta.-adrenoceptors dominate in the distal portion and small artery branches. Apparently the .beta.-adrenoceptors in the coronary vessels differ from the femoral and tracheal .beta.-adrenoceptors in pharmacological feature.