α-ADRENOCEPTORS MEDIATING POSITIVE INOTROPIC EFFECTS ON THE VENTRICULAR MYOCARDIUM: SOME ASPECTS OF STRUCTURE-ACTIVITY RELATIONSHIP OF SYMPATHOMIMETIC AMINES

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概要

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• Experiments were carried out on the isolated papillary muscle of the rabbit in order to further characterize the α-adrenoceptors mediating the positive inotropic effect. For this purpose dose-response relations of seven sympathomimetic amines were compared under the influence of α- and/or β-adrenolytic drugs. Phentolamine (10<SUP>-6</SUP> M) shifted the lower part of the dose-response curves for norfenephrine, synephrine and epinine as for phenylephrine and adrenaline to the right, while prindolol (10<SUP>-8</SUP> M) affected only the upper part of the curves. In the presence of both α- and β-adrenoceptor blocking agents the entire dose-response curves for sympathomimetic amines were shifted in a parallel manner. Noradrenaline affected preferentially β-adrenoceptors, whereas its effect on α-adrenoceptors was so weak that it could be detected only when the neuronal and extraneuronal uptake mechanism of amines were blocked by cocaine (3×10<SUP>-5</SUP> M) and corticosterone (4×10<SUP>-5</SUP> M), respectively. The effect of dopamine was not affected either by phentolamine or by prindolol, but was antagonized by the simultaneous application of both α- and β-adrenoceptor blocking agents. From the present results, it appears that the following relationships are present between the structure of amines and the α-adrenoceptor stimulating activity in the heart: (1) N-methylation increases the potency: (2) Absence of the hydroxyl group either in 3 or in 4 position decreases the intrinsic and β-adrenoceptor stimulating activities, but increases the α-adrenoceptor stimulating activity.

• 社団法人 日本薬理学会の論文

著者

• SCHÜMANN H.J.

  Institute of Pharmacology, University of Essen

• Endoh M.

  Department Of Obstetrics And Gynecology Yokohama City University School Of Medicine

• KRAPPITZ N.

  Institute of Pharmacology, University of Essen

• HILLEN B.

  Institute of Pharmacology, University of Essen

• SCHÜMANN H.J.

  Institute of Pharmacology, University of Essen

• ENDOH M.

  Department of Pharmacology, Tohoku University School of Medicine

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• NO EVIDENCE FOR INVOLVEMENT OF DOPAMINERGIC RECEPTORS IN THE POSITIVE INOTROPIC ACTION OF DOPAMINE ON THE ISOLATED RABBIT PAPILLARY MUSCLE
• α-ADRENOCEPTORS MEDIATING POSITIVE INOTROPIC EFFECTS ON THE VENTRICULAR MYOCARDIUM: SOME ASPECTS OF STRUCTURE-ACTIVITY RELATIONSHIP OF SYMPATHOMIMETIC AMINES

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