Pharmacological Studies on Adrenergic Receptors in Rat Myocardium : Especially on Existence and Function of Alpha-adrenergic Receptors in the Muscle
1979 Volume 31 Issue 3 Pages 377-394
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1979 Volume 31 Issue 3 Pages 377-394
In order to investigate the existence and function of alpha-receptors in myocardium, the effect of noradrenaline (NA) and the influence of tolazoline (TLZ), phentolamine (PTL), propranolol (PRP), or carteolol (CTL) on the NA effect were studied on the isolated rat spontaneously beating atria as well as the electrically driven left atrium and papillary muscle.
NA in concentrations (10-8-10-5 g/ml) increased both the rate and contractile ten sion of spontaneously beating atria as well as the tension of left atrium while transiently decreased the tension of papillary muscle and then increased it.
The dose-response curve for NA of the rate in spontaneously beating atria was shifted downwards by the presence of TLZ in a high concentration (10-5) suggesting the non-competitive antagonization but not influenced by PTL even in the same concentration, while the curve was dose-dependently shifted parallelly to right by low concentrations of either PRP (10-8-10-6) or CTL (10-9-10-7) suggesting the competitive antagonization for NA. The do seresponse curve for NA of the contractile tension in the atria was slightly shifted parallelly to right by PTL (10-8) but shifted non-parallelly downwards by the drug (10-7-40-5) or TLZ (10-8-10-5), while markedly shifted parallelly to right by low concentrations of either PRP or CTL (10-9-10-7).
