Age-related peculiarities of inotropic response of rat myocardium to selective block of M1-cholinoreceptors

In vitro effect of M1-cholinoreceptor blockade on the cardiac inotropic function was examined in rats aging 1, 3, 6, 8, and 20 weeks. In 1- and 3-week old rat pups, the sympathetic control of the heart has not developed, the age of 7-8 weeks being pubertal. Adult 20-week rats were used as the controls. In rats of all age groups, preliminary blockade of M1-cholinoreceptors did not prevent the inhibitory effect of carbacholine on contractility of the atrial and ventricular myocardium. The inhibitory effect of pirenzepine on the contractile force of ventricular myocardium was revealed in 6-week rats. © 2013 Springer Science+Business Media New York

Effects of blockade of hyperpolarization-activated ion currents (Ih) on autonomic control of the heart in rats: Age-related peculiarities

In our experiments, we studied the effects of intravenous introduction of ZD7288, a selective blocker of the currents activated by hyperpolarization (Ih), on the cardial activity of 1- and 3-week-old and young adult (20-week-old) rats. Introduction of the blocker caused a dose-dependent decrease in the heart rate (HR) in all age groups. A maximum and a minimum expression of bradycardia were observed in 1- and 3-week-old rats, respectively. Stimulation of the n. vagus against the background of bradycardia that developed after the blockade of Ih led to a further drop in the HR. In this case, the expression of the effect of stimulation of the n. vagus depended on the dose of the introduced blocker. The blockade of Ih influenced the cardial reaction to introduction of an agonist of β-adrenoreceptors, isoproterenol, in rats of early age and young adult rats, but not in 3-week-old rats. Therefore, the blockade of Ih changes the reaction of the heart on sympathetic and parasympathetic regulatory influences, and the expression of these changes significantly depends on the animal's age. This allows us to conclude that not only the pacemaker activity of cardiomyocytes per se but also autonomic modulation of the cardial activity demonstrate a significant dependence on the function of hyperpolarization-activated ionic channels; this function is characterized by substantial age-related peculiarities. © 2003 Plenum Publishing Corporation

Age-related peculiarities of the effect of α-adrenoceptor blockade on cardiac function in rats

Blockade of α1-adrenoreceptors with prazosin produces bradycardia. The degree of this bradycardia in rats depends on age. In adult (20-week-old) rats bradycardia is pronounced, in 3-week-old rats it is insignificant, and in 1-week-old rats bradycardia does not develop. Prazosin moderates bradycardia induced by vagal stimulation in rats of different age

Language Contact with Crew of Rykyu\u27s Drifting Ships in the Qing Dynasty

The communication between Ryukyu・Okinawa and China has a long history. It has been said that the history has begun even at Ming Dynasty Ryukyu Dynasty were canonized by Chinese king even after Satsuma clan (now Kagoshima Prefecture)\u27s invasion in the beginning of 17 century. The tributary relations between Ryukyu and China had last for 5 centuries until Ryukyu became Okinawa Prefecture by Meiji Japanese government in 1872. The relationship between China and Ryukyu basic were tributary relations. However, the main transportation mean in Ryukyu were by ship，and lots of ship encountered typhoon, lost control of their ship，and finally were drifted to China continent. You can refer to these historical documentation in the book「Selected documentation of China-Ryukyurelations in Qing Dynasty」which was public by China First Historical Archives. Lots of ship-drift cases are written in this book from Qianlong era to Guangxu era of Qing Dynasty. Various forms of transportation can be found form those cases. This paper will not focus on tributary ships from Ryukyu, but on the part of rescue and aid from Qing government to those who were drifted from Ryukyu．文部科学省グローバルCOEプログラム 関西大学文化交渉学教育研究拠点東アジアの歴史と動

Selective blockade of α<inf>2</inf>-adrenoceptor subtypes modulates contractility of rat myocardium

© 2016 Springer Science+Business Media New York.The study examined the dose-dependent effects of selective antagonists of α2A/D-, α2B-, and α2C-adrenoceptors applied in concentrations of 10-9-10-5 M on atrial and ventricular contractility of rat myocardium in vitro. Selective blockade of each α2-adrenoceptor subtype affected the contractile force of the atrial and ventricular strips. Various concentrations of α2A/D-and α2C-adrenoceptor antagonists produced positive inotropic effect on ventricular strips and negative effect on atrial strips. α2B-Adrenoceptor blocker in the majority of the tested concentrations produced a positive inotropic effect in both atria and ventricles

Effect of α2-adrenoceptor stimulation on cardiac activity in rats

We studied the effect of α2-adrenoceptor stimulation with clonidine on BP and cardiac activity in rats. Variations in BP and chronotropism of the heart were studied in vivo after bolus injection of clonidine. In vitro experiments were performed to evaluate a dose-dependent change in myocardial contractility of the atria and ventricles after treatment with clonidine in concentrations of 10-9-10-5 M. α2- Adrenoceptor stimulation with clonidine had a negative chronotropic and inotropic effect and induced the decrease in systolic BP of rats. © 2014 Springer Science+Business Media

Peculiar Effects of Selective Blockade of α2-Adrenoceptor Subtypes on Cardiac Chronotropy in Newborn Rats

© 2015, Springer Science+Business Media New York. We studied the effects of selective blockade of various subtypes of α2-adrenoceptors on cardiac chronotropy in newborn rats. This period in rats is characterized by the absence of adrenergic regulation of heart function. Blockade of α2A/D- and α2B-adrenoceptors in 1-weekold rats provoked tachycardia. In contrast, blockade of α2C-adrenoceptors in newborn rats had no effect on heart rate

Blockade of hyperpolarization-activated channels modifies the effect of β-adrenoceptor stimulation

Experiments on rats showed that blockade of hyperpolarization-activated currents moderates tachycardia induced by β-adrenoceptor agonist isoproterenol and potentiates the increase in stroke volume produced by this agonist. Electrical stimulation of the vagus nerve against the background of isoproterenol treatment augmented bradycardia and increased stroke volume. Blockade of hyperpolarization-activated currents followed by application of isoproterenol moderated vagus-induced bradycardia and had no effect on the dynamics of stroke volume

Effect of Neuropeptide Y on Action Potential Generation in Working Cardiomyocytes of the Right Atrium in Rat Heart

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. We studied the effect of neuropeptide Y in concentrations of 10—8-10—6 M on electrical activity of adult rat right atrial cardiomyocytes with preserved spontaneous activity. Neuropeptide Y was found to modulate the amplitude-time parameters of action potential: in concentrations of 10—7 and 10—6 M it reduced the membrane potential, increased the amplitude of action potential and duration of the repolarization phase, and reduced the frequency of action potential generation. In concentration of 10—6 M, neuropeptide Y produced stronger effect on the analyzed parameters, while in concentration of 10—8 M it produced no significant changes

Peculiar Aspects in Influence of α1-Adrenoceptor Stimulation on Isolated Rat Heart

The study examined the effect of α1-adrenoceptor stimulation with methoxamine on chronotropic function of isolated heart perfused ex vivo according to Langendorff and cardiac chronotropy in vivo. Stimulation of α1-adrenoceptors in isolated heart induced gradually developing bradycardia, which progressed during several minutes. Similar stimulation in vivo produced a short-term bradycardia probably terminated by the compensatory influences in the whole organism. Comparison of the data obtained in both experimental paradigms during α1-adrenoceptor stimulation revealed unidirectional changes in cardiac chronotropy characterized with time-related peculiarities