Comparative Analysis of Cardiac Effects of α<inf>1A</inf>-Adrenoreceptor Stimulation In Vivo and Ex Vivo in Newborn Rats

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. The study examined the effects of α1A-adrenoceptor stimulation on chronotropic function of Langendorff-perfused isolated heart ex vivo and on cardiac chronotropy in vivo in 7-day-old rats. α1A-Adrenergic receptor agonist A-61603 reduced heart chronotropy only in the whole organism. No chronotropic effects of selective stimulation of α1A-adrenergic receptors on isolated hearts were observed in ex vivo experiments. These findings suggest that α1A-adrenergic receptors are not implicated in HR regulation in newborn rats. Bradycardia induced by activation of these receptors in vivo is most likely associated with reflex influences on the heart and changes in the vascular tone in the whole organism

Correction to: Peculiar Aspects in Influence of α<inf>1</inf>-Adrenoceptor Stimulation on Isolated Rat Heart (Bulletin of Experimental Biology and Medicine, (2016), 162, 1, (4-6), 10.1007/s10517-016-3530-z)

Correction to the article “Peculiar Aspects in Influence of α1-Adrenoceptor Stimulation on Isolated Rat Heart,” by T. L. Zefirov, I. I. Khabibrakhmanov, N. I. Ziyatdinova, and A. L. Zefirov, Vol. 162, No. 1, pp. 4-6, November 2016

Alpha(1)-adrenoceptors activation decreases myocardial contractility in newborn rats

© 2020, Editorial board of Journal of Experimental Biology and Agricultural Sciences. All rights reserved. Alpha(1)-adrenergic receptors (α1-AR) are found in cardiomyocytes, endothelial cells, and smooth muscle cells of humans and animals. Despite the fact that α1-AR make up 10% of the total number of adrenergic receptors, these receptors also involved in the regulation of inotropic and chronotropic functions of the heart. According to some scientists, the effects of α1-AR activation are not required for the basal contractile function of the heart while other group of researchers believe that α1-AR can be considered as cardioprotective targets; in particular, it is postulated that the α1A-subtype of adrenergic receptors can provide significant inotropic support in cardiac pathologies. This study was carried out on 6-7-day-old outbred newborn rat pups to evaluate the effect of alpha(1)-adrenoceptors activation on the myocardial contractility in newborn rats. For this, Alpha1-adrenergic receptors were stimulated by the pharmacological drug methoxamine at concentrations of 10-9-10-6 mol and the reaction of the contractile force of the strips of myocardium ventricles and heart atria in response to the agonist was investigated. Results of study revealed that stimulation of alpha1-adrenergic receptors, regardless of the methoxamine concentration, led to a negative inotropic reaction of the myocardium of atria and ventricles of newborn rat pups. This study showed unidirectional inotropic responses on rat atrial and ventricular myocardium in response to α1-adrenergic receptors stimulation. Methoxamine smoothly reduces the contractile force of the strips of myocardium atria and ventricles. At the same time, the concentration dependence on the inotropic reaction of the myocardium was observed. Results of study suggested that probably α1-adrenergic receptors along with the main regulators β-adrenergic receptors carry out fine tuning of the heart activity