Effect of α-Adrenoceptor Stimulation on Functional Parameters of Langendorff-Isolated Rat Heart.

We studied the effect of α-adrenoreceptor agonist clonidine hydrochloride in concentrations of 10-10 M on inotropy, chronotropy, and coronary flow in Langendorff-isolated heart of adult rats. It was found that α-adrenoreceptor agonist changed all studied parameters. Left ventricular myocardium contraction force decreased after application of all tested concentrations, the maximum effect was observed at a concentration of 10 M. Stimulation of α-adrenergic receptors in concentrations of 10, 10, and 10 M produced a two-phase effect (initial increase and a subsequent decrease) on the coronary flow. Clonidine hydrochloride in the maximum concentration (10 M) caused a decrease in HR in one group and an increase in the other.