Related Experiment Video

Updated: Oct 9, 2026

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice
06:22

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice

Published on: September 16, 2015

15.4K

Evidence for participation of catecholamines in cardiac action of ouabain: positive chronotropic effect

E Seifen

    British Journal of Pharmacology
    |August 1, 1974
    PubMed

    Insights

    Ouabain accelerates heart rate in guinea-pig atria by influencing catecholamines and intracellular calcium levels. This positive chronotropic effect is dose-dependent and modulated by beta-adrenoceptor blockade and calcium concentration.

    Area of Science:

    • Pharmacology
    • Cardiovascular Physiology
    • Cellular Biology

    Background:

    • Ouabain is a cardiac glycoside known to affect heart contractility.
    • The precise mechanisms underlying ouabain's chronotropic effects require further elucidation.

    Purpose of the Study:

    • To analyze the positive chronotropic effect of ouabain in isolated guinea-pig atria.
    • To investigate the roles of catecholamines and calcium in mediating ouabain's action.

    Main Methods:

    • Isolated spontaneously beating guinea-pig atria were used.
    • Experiments involved varying ouabain concentrations, beta-adrenoceptor blockade (propranolol), catecholamine depletion (reserpine), and calcium concentrations.

    Main Results:

    • Ouabain exhibited a dose-dependent positive chronotropic effect with a half-time of approximately 20 minutes.
    • The effect was attenuated by beta-adrenoceptor blockade and catecholamine depletion, but partially restored by noradrenaline.
    • Ouabain's action was highly dependent on calcium concentration, with synergistic effects observed.

    Conclusions:

    • Ouabain exerts its positive chronotropic effect through at least two mechanisms: enhancing pacemaker catecholamine concentration and increasing intracellular calcium levels.
    • Calcium concentration plays a critical role in modulating both ouabain and noradrenaline effects on heart rate.

    More Related Videos

    Rodent Working Heart Model for the Study of Myocardial Performance and Oxygen Consumption12:43

    Rodent Working Heart Model for the Study of Myocardial Performance and Oxygen Consumption

    Published on: August 15, 2016

    20.8K
    Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System06:40

    Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System

    Published on: May 21, 2018

    11.1K

    Related Concept Videos

    Adrenergic Agonists: Direct-Acting Agents01:30

    Adrenergic Agonists: Direct-Acting Agents

    Drugs that mimic the action of endogenous catecholamines like noradrenaline and adrenaline are called adrenergic agonists or sympathomimetics. Based on their mechanism of action, sympathomimetics can be classified as direct-, indirect-, or mixed-acting sympathomimetics. Direct-acting adrenergic agonists activate adrenoceptors without affecting presynaptic neurons, making them independent of neuronal catecholamine-depleting agents like reserpine and guanethidine.
    These agents can be classified...
    Adrenergic Agonists: Indirect-Acting Agents01:25

    Adrenergic Agonists: Indirect-Acting Agents

    Indirect-acting adrenergic agonists potentiate the effects of endogenous catecholamines through different mechanisms without directly binding to adrenoceptors.
    One mechanism involves depleting stored catecholamines by displacing them from synaptic vesicles. These agents, known as "displacers," are transported into vesicles at the expense of noradrenaline. Examples include amphetamine and tyramine, which lack a catechol moiety, resulting in prolonged action, improved oral bioavailability, and...
    Mechanism of Cardiac Arrhythmias01:28

    Mechanism of Cardiac Arrhythmias

    Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
    Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers01:24

    Antiarrhythmic Drugs: Class II Agents as β-Adrenergic Blockers

    Adrenergic stimulation generally impacts cardiac rate and rhythm. Specifically, stimulation of the β-adrenoceptors triggers an increase in intracellular calcium ion influx and pacemaker currents, which may cause arrhythmias. Catecholamines like adrenaline also demonstrate β2-adrenoceptor-mediated hypokalemia, impacting cardiac action potential and disrupting the normal cardiac rhythm. Class II antiarrhythmic drugs are β-adrenoceptor antagonists or β-blockers, which indirectly block calcium...
    Pathophysiology of Cardiac Performance01:29

    Pathophysiology of Cardiac Performance

    Typical heart performance is influenced by heart rate, rhythm, myocardial contraction, and metabolism or blood flow. The cardiac muscle exhibits distinct electrophysiological features, including pacemaker activity and calcium channel control, which play a vital role in the heart's response to various drugs. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate. Sympathetic activation increases heart rate, while parasympathetic activation...
    Heart Failure Drugs: Inotropic Agents01:26

    Heart Failure Drugs: Inotropic Agents

    Positive inotropic agents are commonly used as the first line of treatment for heart failure. One such agent is digoxin, derived from the genus Digitalis, which has been known for centuries but effectively utilized since 1785. However, these cardiac glycosides can have potentially toxic effects due to their mechanism of action, which involves inhibiting Na+/K+-ATPase and increasing contractility. Digoxin is absorbed orally and distributed in various tissues, including the CNS. It has a long...