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

Effect of Clonidine Hydrochloride on Isolated Newborn Rat Heart

The concentration dependenies of the chronotropic response and changes in blood supply to the isolated heart of 7-day-old newborn rats induced by application of α2-adrenergic receptor agonist clonidine hydrochloride in concentrations of 10-9-10-6 M were revealed. The minimum concentration of α2-adrenergic receptor agonist caused tachycardia, while higher concentrations led to bradycardia. The maximum effect manifesting in a decrease in coronary flow was recorded at the minimum concentration of the agonist, while the highest concentration had no effect on the coronary flow. When comparing these results with those obtained in control adult rats, we found that the most pronounced differences in the chronotropic effects were observed after addition of the minimum concentration of the α2-adrenergic receptor agonist: bradycardia in adult rats and tachycardia in newborns. The maximum differences in coronary flow parameters were observed after addition of α2-adrenergic receptor agonist in the maximum concentration that induced a two-phase response in adult rats and had no effect on the blood supply in newborns

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

Effect of α2-Adrenergic Receptor Stimulation on the Isolated Rat Heart against the Background of I<inf>f</inf> Blockade

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. The study examined the effect of α2-adrenoreceptor (α2-AR) activation against the background of preliminary blockage of If on the performance of Langerndorff-isolated rat heart. Stimulation of α2-AR in isolated rat hearts against the background of ZD7288 in concentrations of 10—9 M and 3×10—5 M changed the negative dynamics of myocardial inotropy to positive (by 25 and 38%; p'0.05). Activation of α2-AR produced opposite effects on HR. If blockade abolished tachycardia caused by activation of α2-AR; HR deceleration in response to α2-AR agonist against the background of If blocker in a concentration 10—9 M was 41% (p'0.05). We observed negative dynamics of coronary flow (by 38%; p'0.05) in isolated adult rat hearts after application of α2-AR agonist against the background of If blockade (10—9 M)

ATP inhibits the spontaneous contractility of atria in rats

ATP is a multifunctional nucleotide. In recent years, strong evidence has accumulated that ATP may participate in intercellular signaling, where ATP acts as a cotransmitter. ATP participation in the regulation of physiological functions in the organism is carried out through specific purinoreceptors, which were found in many tissues of the organism, including the heart. The aim of our research was to study the role of ATP at different concentrations on the parameters of electrical activity and the contractility of the myocardium of the right atrium of rats with a preserved sinus node. The experiments were performed on the myocardium of the right atrium of rats with spontaneous activity. Isometric reduction and electrical activity of the drugs were recorded. ATP at the concentration of 10–8 M caused no significant changes in the parameters under study. ATP at the concentration of 10–7 M caused two-phase changes in the amplitude-time parameters of myocardial contractility and electrical activity of the right atrium myocardium. In the first minutes of the experiment, ATP caused an increase in the frequency and strength of myocardium contraction and the duration of the action potential at the level of 20, 50, and 90% repolarization. By the 15th minute, the studied parameters were restored. ATP at the concentration of 10–6 M caused a negative inotropic and chronotropic effect, through the activation of adenosine receptors

The role of catecholamins in the regulation of children's body hemodynamic

© 2020, Hampstead Psychological Associates. All rights reserved. The catecholamine system stands out among other hormonal systems by its participation in the regulation of hemodynamic functions. In children, the level of hormones and mediators is not constant, which explains the lack of formation of the mechanisms of regulation of the circulatory system. Long-term static postural stress of the child at school and home causes rapid muscle fatigue and mental stress, which does not exclude vegetative dysfunctions and abnormalities in the cardiovascular system (CVS). Conducted a comprehensive study of the state of hemo dynamics and adrenal glands in children 7 years old, an analysis of the correlations between their parameters. Daily and portioned urine was collected in spring and autumn, and the levels of adrenaline (A), norepinephrine (NA), dopamine (DA) and DOPA were recorded by fluorometry. The state of the circulatory system was studied by indicators of cardiac output-stroke volume of blood (CLC) and minute circulation-IOC. Thoracic rheoplethysmography with an analog-to-digital converter was used. Peripheral circulation was recorded by analysis of blood pressure (systolic, diastolic and mean hemodynamic blood pressure (SBP), (DBP) and (SRS). The method of pair correlation was used to study the interdependence of indicators of the endocrine system and the circulatory system. The relationship of the hormones of the adrenal medulla and the parameters of the CVS of the child's body is shown. This was most clearly manifested in the state of the functional stress of the body, a variant of which was the dosed static load. A relationship was found between the hemodynamic reaction and the level of excretion of catecholamines (CA) and DOPA in the post-isometric period. Isometric muscle tension of the upper limb causes an increase in the tone of peripheral vessels and a parallel increase in NA in children of 7 years of age. At the same time, at the end of the school year, there is a negative dynamics in the excretion of A, NA, and DA, accompanied by a decrease in the CRF and IOC in the recovery period. A decrease in the activity of adrenergic influences on the pumping function of the heart is indicated by a break in the correlation bonds of A and NA with UOK and IOC. Thus, the study allowed us to identify the relationship between hemodynamic parameters and the level of catecholamine excretion in the post-isometric period in children 7 years old. The effect of NA on the state of peripheral vascular tone has been proven, unidirectional changes in the level of NA excretion and DBP values, total peripheral vascular resistance (OPSS) after static muscular effort have been established

Influence of HCN channels on isolated heart functions in adult rats

Heart pacemaking has triggered a research interest for many decades. Hyperpolarization-activated currents (If) and ion channels (HCN channels) that provide this current are widespread in the central and peripheral nervous system. In atypical cardiomyocytes, HCN channels generate a spontaneous electrical activity. The physiological role of HCN channels in the working myocardium remains a subject of constant research. The expression of HCN channels in cardiomyocytes of the ventricles was shown. It is possible that If participates in the formation of the potential action of working cardiomyocytes and, consequently, in the regulation of the inotropic cardiac function. The study was performed in order to investigate the role of hyperpolarization-activated currents on chronotropy, inotropy, and coronary flow of the Langendorff heart in adult rats. Experiments ex vivo were performed on random-bred albino rats aged 20 weeks. The heart was perfused in the Langendorff System (ADInstruments). The coronary flow, left ventricular pressure, and heart rate were calculated along the curve. 10–9 – 3?10–5 М concentrations range of ZD7288 (Sigma) were used for If blockade. The analysis of the results demonstrated that the left ventricular pressure increased after the blockade of If at the concentration of 10–9 M and decreased with the blocker concentration of 3?10–5 M. The ZD7288 caused bradycardia of the isolated heart at the concentrations of 10–9, 10–6, 3?10–5 M. The isolated heart coronary flow decreased with the blockade of If at the concentration of 10–9 M and 3?10–5 M. It was concluded that If blockade changes chronotropy, inotropy, and coronary flow of the isolated heart in adult rats

Studies of Nitric Oxide Production in Rat Tissues in Postnatal Development by Electron Paramagnetic Resonance Spectroscopy

Paramagnetic complexes containing nitric oxide (NO) have been assayed in rat heart and liver tissues by EPR spectroscopy to investigate the time variation of NO production during postnatal development. Nitric oxide levels have been assessed from the intensity of a characteristic EPR signal belonging to the (DETC)2–Fe2+–NO complex. The results show that the content of NO in liver tissues increases within the age interval from 28 to 56 days but does not change significantly in postadolescence. In heart tissues, the nitric oxide level increases in adulthood compared to puberty. The NO level in the rat liver is significantly higher than in heart tissues in all studied age groups