Pharmacological Analysis of Dopamine Action on the Isolated Dog Atrium

Chiba, Shigetoshi

doi:10.1620/tjem.115.355

Cited by 10 publications

(2 citation statements)

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“…In the present study by use of isolated atria, we confirmed that dobutamine-induced positive chronotropic and inotropic effects were not modified by treatment with imipramine, although tyramine induced ones were markedly suppressed and dopamine-induced ones were slightly but significantly sup pressed as reported previously (9). Therefore, it was confirmed that dobutamine, unlike dopamine and tyramine, has no releasing action of norepinephrine.…”

Section: Discussionsupporting

confidence: 92%

“…Moreover, an intra-arterial injection of dobutamine to the isolated atrium caused more potent chrono tropic and inotropic effects than that of dopamine, with essentially the same pattern of response as that to isoproterenol. In isolated atrial preparations, the ratio of the inotropic effect to the chronotropic effect for each dose of the drugs was studied in our previous reports (7)(8)(9)(10). Figure 7 shows the ratio for dobutamine determined in the present study as well as the ratios for other drugs determined in both present and previous studies.…”

Section: Discussionmentioning

confidence: 51%

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Cardiovascular effects of dobutamine, dopamine and isoproterenol on the whole animal and isolated cross-perfused atrium in dogs.

et al. 1983

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Abstract-The right atrium of the dog was isolated and cross-perfused with arterial blood of another (donor) dog anesthetized with pentobarbital. When dobutamine, dopamine or isoproterenol was administered intravenously to the donor dog, the following changes were elicited in them: Dobutamine caused slight biphasic changes in heart rate. Dopamine induced biphasic changes in blood pressure and heart rate. Isoproterenol produced a decrease in blood pressure and a marked increase in heart rate. All these 3 catecholamines, however, induced positive chronotropic and inotropic effects in a similar fashion on the isolated atrium cross-perfused with blood of the donor dog. When injected into the cannulated sinus node artery of the isolated dog atrium, dobutamine, dopamine or isoproterenol induced monophasic positive chronotropic and inotropic effects in a dose-related manner, although the potency of each of the drugs was different. Dobutamine-induced effects were abolished by propranolol, but not modified by imi pramine which suppressed significantly tyramine-and dopamine-induced effects. The difference in dobutamine-induced chronotropic effect between the whole animal and the isolated atrium may be due mainly to modification by extracardiac factors in the whole animal.Dobutamine is a synthetic catecholamine developed by Tuttle and Mills (1) to provide a clinically more useful inotropic agent having less side effects. Indeed, dobutamine directly increases myocardial contractility without inducing marked tachycardia or greatly changing peripheral arterial resistance in intact dogs (1-3). In the cat papillary muscle, dobutamine increases the con tractility more but the automaticity less than did isoproterenol (1). However, no report is available concerning the effect of dobutamine assessed in isolated dog heart preparations. Thus, in the present study, we attempted to compare chronotropic and inotropic effects of dobutamine, dopamine and isoproterenol using the isolated dog atrial preparation which was perfused with the arterial blood of the donor dog (4, 5). We administered these three catecholamines intravenously to the donor dog or intraarterially to the isolated atrium to observe their direct cardiac chrono tropic and inotropic effects and probable modification of these effects by extracardiac factors. Materials and MethodsTwenty mongrel dogs weighing 11-25 kg were anesthetized with sodium pentobarbital (30 mg/kg, i.v.). The right atrium was quickly removed and immersed in Tyrode solution at 4-10°C. The right atrium was then perfused with blood from the carotid artery of a heparinized donor dog. Perfusion pressure was kept constant at 100 mm Hg. The atrium which was usually subjected to a resting tension of 2 g was suspended in the bath filled with blood maintained at a constant temperature of 37'C. Atrial rate and isometric tension development of the isolated atrium and systemic blood pressure and heart rate of the donor dog were simultaneously measured during the experiments. The details of the preparation are descri...

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 51%

Cardiovascular effects of dobutamine, dopamine and isoproterenol on the whole animal and isolated cross-perfused atrium in dogs.

et al. 1983

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Studies on the positive inotropic effect of dopamine in the guinea-pig heart

Mugelli

Ledda

Mantelli

et al. 1977

Naunyn-Schmiedeberg's Arch. Pharmacol.

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The positive inotropic effect of dopamine has been studied in isolated ventricular strips of guinea-pig heart. The concentration-inotropic response curve for dopamine was significantly shifted to the right by pretreatment with reserpine. In preparations obtained from animals pretreated with reserpine (2.5 mg/kg, 24 h prior to the experiment) the dose-response curve was not significantly affected by haloperidol, a dopamine vascular receptor antagonist (10(-6)-3X10(-6) M). The inotropic effect of dopamine was antagonized by practolol (3X10(-7)-10(-6) M), but not by phentolamine (3X10(-6)-10(-5) M); moreover the alpha-adrenoceptor blocking drug (10(-5) M) did not affect the curve for dopamine in the presence of practolol (3X10(-7) M). In preparations in which fast sodium channels were blocked by K+ -rich medium, slow electrical responses (calcium-mediated action potentials) as well as contractions were induced by high concentrations of dopamine (10(-4)-3X10(-4) M); again these responses were unaffected by phentolamine or haloperidol, but were blocked by practolol. It was concluded that in the guinea-pig ventricular muscle dopamine induced a positive inotropic effect through both indirect and direct action, and that the latter is due to the activation of beta-adrenoceptors.

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