Peracute Myocardial Infarction: Features of the Influence of α-Adrenoreceptor Stimulation on the Isolated Heart.

We performed a comparative analysis of the effect of α-adrenoreceptor stimulation on the performance of Langendorff-isolated heart from rats with experimental myocardial infarction in the acute stage and sham-operated animals (control). In animals with peracute myocardial infarction, different agonist concentrations (clonidine, 10 and 10 M) produced a multidirectional effect on the left-ventricular developed pressure and speed and time parameters of heart contractility. In control rats, both concentrations of the agonist added to the perfused solution reduced contraction force.

Features of α-Adrenergic Regulation of Isolated Rat Heart after Hypokinesia.

We studied the effect of the α-adrenergic receptor agonist clonidine hydrochloride (10-10 M) on the isolated heart of adult rats after 30-day restriction of motor activity. In hypokinetic rats, in comparison with control animals, clonidine caused a positive inotropic effect; the dynamics of coronary flow was changed after stimulation of α-adrenergic receptors by clonidine in the minimum and maximum concentrations. Moreover, clonidine in concentrations of 10 and 10 M reduced coronary flow both in the control group and against the background of hypokinesia.

Effect of Adrenoreceptor Stimulation on Peptidergic Regulation of Cardiac Activity in Newborn Rats.

We studied the effect of adrenoreceptor stimulation on the frequency of spontaneous activity and amplitude-time parameters of isometric contraction of the atrial myocardial strips from newborn rats, as well as the effect of Y receptor stimulation against the background of adrenoreceptor activation. After addition of Y receptor agonist [Leu31, Pro34] NPY (10 M), a tendency to a decrease in the effect of β-adrenoreceptor agonist isoproterenol (10 M) on the frequency of spontaneous activity and atrial myocardial contractility was observed. The age-related features of the effect of NPY on the frequency of spontaneous activity and contractility of myocardial strips from newborn and adult rats were revealed.

α-Adrenergic Receptor Blockade Inhibits Langendorff-Isolated Rat Heart Work.

We studied the effect of selective α-adrenergic receptor antagonist JP-1302 in concentrations of 10-10 M on inotropy, chronotropy, and coronary flow in the Langendorff-isolated rat heart. JP-1302 in all studied concentrations decreased the left-ventricular myocardium force contraction, HR, and coronary flow. The maximum inotropic, chronotropic, and vascular effects were observed when the antagonist was applied to the perfused solution in a concentration of 10 M.

Mechanisms of Modulation of Adrenergic Regulation of Spontaneous Activity Rate and Atrial Myocardial Contractility in Early Postnatal Ontogeny in Rats.

We studied combined effect of the β-adrenoreceptor agonist isoproterenol and the Y receptor agonist [Leu31, Pro34]neuropeptide Y on the frequency of spontaneous activity and myocardial contractility in 21- and 100-day-old rats. Isoproterenol increased the frequency of spontaneous activity and reduced the main parameters of isometric contraction of the atrial myocardium. When [Leu31, Pro34]neuropeptide Y was added, the frequency of spontaneous activity and the negative inotropic and the positive chronotropic effects of isoproterenol were reduced in 100-day-old rats.