Influence of dopamine on inotropy of the myocardium with nonselective blockade of α-adrenergic receptors

Monoamine dopamine activates D1 and D2 dopamine receptors, which are found in human and rat heart and dopamine interact with α- and β-adrenoceptors. Were conducted in vitro studies on the effect of dopamine at concentrations of 10–9 M to 10–5 M-force reduction of isolated atrial myocardium and ventricular strips rats 56-, 70- and 100-day age when non-selective alpha-adrenergic blockade phentolamine. Isometric contraction of myocardial strips atria and ventricles were recorded on the installation «Power Lab». All experiments were performed in compliance with the bioethical rules.

When α-adrenergic blockade of dopamine at a dose of 10-5 M causes an increase in the atrial myocardium of rats 56-, 70- and 100 days age. On the background of adrenoceptor blockade in 56-day-old rat ventricular myocardial contractility increases, while the 70- and 100-day conversely decreases. Dopamine concentrations 10-6M – 10-8M reduces the force of contraction myocardium as the strips atria, ventricles and rats of all ages studied. Dopamine in the 10-9 M concentration increases myocardial contractility atria and ventricles in 57 and 70-day-old rats. At the 100-day-old animals at this concentration takes place a reliable decrease force of contractility as the atrial myocardium, and the ventricles.

Thus non-selective blockade of the alpha-adrenergic receptors alters the effect of phentolamine dopaminergic rehulation of the heart formed with sympathetic innervation.