Effect of Hemicholinium on the Release of Autonomic Mediators in the Sinoatrial Node

Vincenzi, Frank F.; West, Theodore C.

doi:10.1111/j.1476-5381.1965.tb01633.x

Cited by 13 publications

(22 citation statements)

References 8 publications

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“…2 and 5). Other authors have demonstrated similar duration and/or frequency dependent effects of vagal stimulation on membrane hyperpolarization, chronotropic responses of the SA node and dromotropic responses of the AV node (Vincenzi and West, 1965;West and Toda, 1967;Chess and Calaresu, 1974;Jalife et al, 1980;Martin et al, 1982).…”

Section: Duration-and Frequency-dependence Of the Fadementioning

confidence: 66%

"Fade" of hyperpolarizing responses to vagal stimulation at the sinoatrial and atrioventricular nodes of the rabbit heart.

Salata

Jalife

1985

Circulation Research

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SUMMARY. Previous studies have suggested that maintained vagal stimulation or acetylcholine infusion results in a fade of responses in the sinoatrial node but not in the atrioventricular node, implying different muscarinic receptor subtypes in the two regions. We investigated this hypothesis in 23 isolated rabbit atrial preparations made quiescent by continuous superfusion with verapamil (1 jtg/ml). Transmembrane potentials were recorded simultaneously from cells in the sinoatrial pacemaker region and from the "N" region of the atrioventricular node. Postganglionic vagal stimulation was achieved by the application of trains of pulses (50-150 ^sec; 10-20 V; 200 Hz). Simultaneous application of long-lasting (1-10 sec) vagal trains produced hyperpolarizations which were nearly identical for both nodal regions. Maximal hyperpolarizations (~ 24 mV for sinoatrial node; 26 mV for atrioventricular node) were reached about 500 msec after initiation of the vagal train. Thereafter, hyperpolarizations faded, following a biphasic time course, and thus displaying two different time constants, one fast (Tf as , = 580 msec for sinoatrial node; 550 msec for atrioventricular node), and one slow (T S1OW = 9.2 sec for both sinoatrial and atrioventricular nodes). Hyperpolarizations during brief (200-msec) but repetitive vagal trains also faded biphasically, but approached a steady state much more rapidly than responses to long-lasting trains. Recovery from hyperpolarization decay occurred rather slowly and was linear. Our results demonstrate that the membrane potential responses to vagal stimulation in the atrioventricular node are indistinguishable from those in the sinoatrial node, and suggest that similar muscarinic receptors are operative in both regions. These phenomena may play an important role in the response of the cardiac conducting system to direct or reflexly mediated vagal input. (Circ Res 56: 718-727, 1985)

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Section: Duration-and Frequency-dependence Of the Fadementioning

confidence: 66%

"Fade" of hyperpolarizing responses to vagal stimulation at the sinoatrial and atrioventricular nodes of the rabbit heart.

Salata

Jalife

1985

Circulation Research

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“…Tetrodotoxin, which blocks fast Na channels (20), suppresses Purkinje fibers (15,21) but not sinus node cells (15,22,23). High Ca decreases the rate of spontaneous discharge of Purkinje fibers (24) but increases that of the sinus node (19,(25)(26)(27)(28)(29), even after abolition of autonomic influences (25,28,29). Although the slowing in Purkinje fibers is due to a shift in threshold (24), the acceleration in the sinus node is due to a steepening of diastolic depolarization (25,27).…”

Section: Discussionmentioning

confidence: 99%

Role of the Sympathetic Nervous System in the Sinus Node Resistance to High Potassium

Vassalle

Greineder

Stuckey

1973

Circulation Research

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The resistance of sinus node automaticity to high potassium (K) levels was studied in anesthetized dogs by perfusing the sinus node artery with oxygenated Tyrode's solution containing different K concentrations. The following results were obtained.(1) Sinus node automaticity persisted at a K concentration of 21.6 DIM, although the pacemaker site tended to shift in and out of the node at this concentration. (2) Sinus node dominance at high K concentrations was progressively lost as sympathetic influences were progressively eliminated. (3) Sinus node pacemaker activity was suppressed at a K concentration lower than 21.6 mM when calcium was omitted from the perfusion fluid. (4) The pacemaker site shifted consistently from the sinus node towards the atrioventricular node at high K concentrations after the elimination of sympathetic activity (5) The transient sinus tachycardia caused by high K concentrations persisted after bilateral vagotomy. It is concluded that catecholamines participate in the resistance of the sinus node to K, suggesting that the difference in resistance to high K concentrations between the sinus node and Purkinje fibers may, in part, result from the more abundant innervation of the sinus node. KEY WORDScatecholamines reserpine sympathectomy propranolol calcium dog• Ventricular Purkinje fibers perfused in vitro usually become quiescent when the potassium (K) content of Tyrode's solution is increased from 2.7 mM to 5.4 mM (1). In contrast, the sinus node continues to discharge spontaneously when K is increased to a concentration at which atrial fibers become inexcitable (2-6). The reason for the resistance of sinus node pacemaker activity to high K concentrations is not understood. It seems likely that this resistance to K reflects membrane characteristics peculiar to sinus node cells, but other factors cannot be excluded. One of these factors could be sympathetic innervation, since it has been shown that catecholamines counteract the depressant effect of K on cardiac excitability (4, 7). It does not seem unreasonable, therefore, to propose that catecholamines also counteract the depressant effect of K on automaticity. Sympathetic innervation of ventricular Purkinje fibers is sparse and that of the sinus node abundant (8) This work was supported in part by grants from the U. S. Public Health Service and the New York Heart Association. The work was carried out while Dr. Vassalle was the recipient of a Sinsheimer Award.A preliminary report has appeared in abstract form (Am J Cardiol 26:636, 1970).Received September 22, 1972. Accepted for publication January 11, 1973. reinforces the possibility that catecholamines play an important role in the difference in sensitivity between atrial and ventricular pacemakers to K.The aim of the present investigation was to study the effect of the sympathetic nervous system on the sinus node resistance to high K concentrations by perfusing the sinus node artery with a solution in which K content was varied. Autonomic denervation, catecholamine depletion...

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“…Spontaneous, extracellularly recorded, action potentials were used for measuring the interval between beats with a device described earlier (21). The following values were recorded: steady state interval (i.e., the interval between beats before nerve stimulation); maxi mal beat interval during the cholinergic response, and minimum beat interval during adrenergic response.…”

Section: Methodsmentioning

confidence: 99%

“…Transmural stimulation of isolated spontaneously beating sinoatrial node from adult hearts, results in a biphasic chrono tropic response consisting of both cholinergic and adrenergic components (2,21). The present work employed transmural stimulation for studying the functional capacity, in the perinatal period, of intranodal nerve fibers of rabbit, guinea pig and rat.…”

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confidence: 99%

Functional Autonomic Innervation of Mammalian Cardiac Pacemaker during the Perinatal Period

Vlk¹,

Vincenzi²

1977

Neonatology

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Sinoatrial node pacemaker tissues from perinatal and adult rabbits, guinea pigs and rats were examined in vitro. Changes in spontaneous pacemaker rate produced by stimulation of intranodal vagal and sympathetic nerve endings, were taken as a measure of functional postganglionic innervation of the pacemaker. Results show marked species differences in the development of functional innervation of the cardiac pacemaker in the perinatal period.

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Effect of Hemicholinium on the Release of Autonomic Mediators in the Sinoatrial Node

Cited by 13 publications

References 8 publications

"Fade" of hyperpolarizing responses to vagal stimulation at the sinoatrial and atrioventricular nodes of the rabbit heart.

"Fade" of hyperpolarizing responses to vagal stimulation at the sinoatrial and atrioventricular nodes of the rabbit heart.

Role of the Sympathetic Nervous System in the Sinus Node Resistance to High Potassium

Functional Autonomic Innervation of Mammalian Cardiac Pacemaker during the Perinatal Period

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