α<sub>1</sub>‐Adrenoceptors in the conduction system of rat hearts

In acute experiments on rats of different ages (21, 30, 42, and 70 days), the ot~-adrenoblocker prazosin increased the heart rate (HR), and the [3-blocker propranolol (Obsidan) infused after prazosin reduced this parameter. Prazosin decreased both stroke volume and cardiac output, blockade of 13-adrenoceptors further decreased these parameters. It is concluded that both ot~-and [3-adrenoceptors are involved in the sympathetic regulation of cardiac output in developing animals.Key Words: at 1-and ~-adrenoceptors; prazosin; stroke volume; developing rats; heart rate Adrenergic regulation of chronotropic and contractile cardiac functions is known to be mediated by c~-and 13-adrenoceptors (AR) [4,6,9]. Atrial and ventricular cardiomyocytes in rats express different al-AR subtypes [10][11][12]16]. In rat heart, the positive inotropic effect of epinephrine is realized primarily via a~B-AR through modulation intracellular Ca 2+ concentration [12]. The ratio for A and B subtypes of a~-AR in rat heart is 20:80 [ 15]. Sustained positive inotropic effects of o~l-agonists on the atria and ventricles in rat heart are mediated by activation of both otI-AR subtypes of [15]. Several studies investigated the role of [3-AR in the regulation of stroke volume (SV), cardiac output (CO) and heart rate (HR) in the developing organism [1,2,4,5]. At the same time, the role of ot~-AR in in vivo regulation remained little studied and was the subject of our study. MATERIALS AND METHODSExperiments were carried out on outbred albino rats at the age of 21, 30, 42, and 70 days. Stroke volume was measured by a modified technique of tetrapolar chest rheography [1,3,8]. Differential rheogram was recorded by an RPG-204 apparatus in animals ariesKasan' State Pedagogical University; Kasan State Agricultural Academy thetized with Nembutal (40 mg/kg) under conditions of natural ventilation. Cardiac output was calculated from SV and HR. Prazosin (10 -7 tool/liter) in a dose of 0.17 mg/100 g and propranol (Obsidan, 0.1% solution) in a dose of 0.8 rag/100 g were used. The drugs were infused through a catheter into the jugular vein. The second drug was administered after the changes in HR induced by the first preparation attained the maximum.In series I, AR were blocked first with propranolol and then with prazosin; in series II the order of infusions was inverted.The data were analyzed statistically using Student's t test.

show abstract

“…The density of cz,-AR in the sinoatrial and atrioventricular nodes is higher than in the myocardium [14].…”

Section: Resultsmentioning

confidence: 72%

“…This implies that ot,-AR play an important role in the regulation of not only inotropic, but also chronotropic function of the heart [14].…”

Section: Resultsmentioning

confidence: 99%

Cardiac output in rats of different ages during blockade of α1 and β-adrenoceptorsand β-adrenoceptors

Нигматуллина¹,

Abzalov²,

Minnibaev³

1999

Bull Exp Biol Med

View full text Add to dashboard Cite

show abstract

“…The density distribution for dopamine and adrenergic receptors in the median region of SAN central part coincided, the higher density of the ligand binding sites being determined by cross-reaction processes. No asymmetry for α 1 - [13] and β-adrenoreceptors (reference in [4]) was observed in rat SAN, though the number of these receptors in SAN was higher than in working atrial myocardium. A vast accumulation of 3 H-dopamine binding sites was observed in the median region opposite to the initial PMR; maximum binding of 3 H-dopamine was registered for the SAN arterial wall (Fig.…”

Section: Resultsmentioning

confidence: 74%

Topography of 3H-DHA, 3H-QNB, 3H-Dopamine, and 3H-DAGO Binding Sites Distribution in the Central Part of the Sinoatrial Node in Rat Heart

2005

View full text Add to dashboard Cite

The topography of distribution of 3H-dihydroalprenolol, 3H-quinucledinyl benzilate, 3H-dopamine, and 3H-DAGO binding sites in the central part of the sinoatrial node in rat heart was studied by autoradiography after electrophysiological identification of the dominant pacemaker region location. Receptor asymmetry between the lateral and median regions of the central part of the sinoatrial node was shown. The dominant pacemaker region lay in the lateral area of the sinoatrial node; the number of binding sites for all four ligands was minimum in it. The number of binding sites gradually increased in the cranial and caudal directions from the dominant pacemaker region along the sinoatrial node artery (more smoothly in the caudal direction). The relative densities of bindings sites for 3H-dihydroalprenolol and 3H-dopamine were higher in the lateral region compared to the perinodal working myocardium, while the densities for 3H-quinucledinyl benzilate and 3H-DAGO were virtually the same. The distribution of binding sites along the artery in the median region of the sinoatrial node was even for 3H-quinucledinyl benzilate and 3H-DAGO. For 3H-DAGO these parameters were close to those in the perinodal atrial myocardium, for 3H-quinucledinyl benzilate somewhat lower. Curves presenting the distribution of binding site densities for 3H-dihydroalprenolol and 3H-dopamine in the median region of the sinoatrial node were similar, with a pronounced peak in the region contralateral to the dominant pacemaker region, and significantly higher binding parameters compared to those for the perinodal atrial myocardium. The difference consisted in higher density of 3H-dopamine binding sites in the median region of the sinoatrial node in comparison with the lateral region. Binding activity was maximum in the wall of the sinoatrial node artery. The distribution of binding sites for ligands to the main autonomic nervous system neurotransmitters in the rat heart sinoatrial node is heterogeneous.

show abstract

“…For instance, in isolated SAN from both young and adult rabbits, phenylephrine (which activates α-AR) does not alter HR (Hewett and Rosen, 1985). Despite this result, greater expression of α-AR occurs in the SAN compared to surrounding myocardium in rat, suggesting a role for α-AR in HR control (Saito et al, 1994).…”

Section: Catecholaminesmentioning

confidence: 80%

Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans

2020

View full text Add to dashboard Cite

The sinoatrial node is perhaps one of the most important tissues in the entire body: it is the natural pacemaker of the heart, making it responsible for initiating each-andevery normal heartbeat. As such, its activity is heavily controlled, allowing heart rate to rapidly adapt to changes in physiological demand. Control of sinoatrial node activity, however, is complex, occurring through the autonomic nervous system and various circulating and locally released factors. In this review we discuss the coupled-clock pacemaker system and how its manipulation by neurohumoral signaling alters heart rate, considering the multitude of canonical and non-canonical agents that are known to modulate sinoatrial node activity. For each, we discuss the principal receptors involved and known intracellular signaling and protein targets, highlighting gaps in our knowledge and understanding from experimental models and human studies that represent areas for future research.

show abstract

α₁‐Adrenoceptors in the conduction system of rat hearts

Cited by 10 publications

References 20 publications

Cardiac output in rats of different ages during blockade of α1 and β-adrenoceptorsand β-adrenoceptors

Cardiac output in rats of different ages during blockade of α1 and β-adrenoceptorsand β-adrenoceptors

Topography of 3H-DHA, 3H-QNB, 3H-Dopamine, and 3H-DAGO Binding Sites Distribution in the Central Part of the Sinoatrial Node in Rat Heart

Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans

Contact Info

Product

Resources

About

α1‐Adrenoceptors in the conduction system of rat hearts

Cited by 10 publications

References 20 publications

Cardiac output in rats of different ages during blockade of α1 and β-adrenoceptorsand β-adrenoceptors

Cardiac output in rats of different ages during blockade of α1 and β-adrenoceptorsand β-adrenoceptors

Topography of 3H-DHA, 3H-QNB, 3H-Dopamine, and 3H-DAGO Binding Sites Distribution in the Central Part of the Sinoatrial Node in Rat Heart

Neurohumoral Control of Sinoatrial Node Activity and Heart Rate: Insight From Experimental Models and Findings From Humans

Contact Info

Product

Resources

About

α₁‐Adrenoceptors in the conduction system of rat hearts