Effects of localized stretch of the sinoatrial node region of the dog heart

Brooks, CM; Lu, HH; Lange, Gertrude; Mangi, Richard J.; Shaw, RB; Geoly, K

doi:10.1152/ajplegacy.1966.211.5.1197

Cited by 76 publications

(30 citation statements)

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“…As found in previous experiments performed on denervated atrium and isolated SA nodal tissue (LUDWIG and LUCHSINGER, 1881;BLINKS, 1956;DECK, 1963;BROOKS et al, 1966;LANGE et al, 1966), the increase in the pacemaker frequency was always observed by stretch or load application of isolated rabbit SA nodal tissue with normal discharge frequency of 200-250/min. The literature Japanese Journal of Physiology i imt Fig.…”

Section: Discussionsupporting

confidence: 83%

Length-dependent changes of pacemaker frequency in the isolated rabbit sinoatrial node.

1984

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To correlate changes in pacemaker frequency with those of length and tension in mammalian atrial tissues, a strip of the sinoatrial (SA) nodal tissue (about 10 mm in length and 4 mm in width) isolated from the rabbit heart was subjected to constant-length and constantload stretches, and the relation between the resulting pacemaker frequency changes and the segmental length changes of the preparation was examined by means of cinematographic recording of the preparation with carbon markers on its surface. The amount of stretch-induced length changes was larger in the perinodal tissue segments than in the SA nodal segments, indicating that the nodal area is less extensible than the perinodal area. The time course of stretch-induced length changes of one nodal segment (closer to the inferior versa cava) was found to roughly parallel that of pacemaker frequency changes, suggesting that the pacemaker frequency is primarily dependent on the length but not on the tension of the SA nodal area.

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Section: Discussionsupporting

confidence: 83%

Length-dependent changes of pacemaker frequency in the isolated rabbit sinoatrial node.

1984

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“…However, our study indicates the existence of a biphasic response in sympathetic neuronal discharges and in the heart rate caused by stretching the left atrium. We also wish to emphasize the presence of a myogenic contribution totheaccelerator response initiated by stretching the right atrium (8,14). These two findings must partly explain the basis for the previously mentioned conflicting results reported by various investigators (2,3,6).…”

Section: Discussionmentioning

confidence: 81%

Centers involved in the autonomic reflex reactions originating from stretching of the atria.

Koizumi¹,

Nishino²,

Brooks³

1977

Proc. Natl. Acad. Sci. U.S.A.

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Stretching the atria in anesthetized dogs produces reflex changes in heart rate, and in cardiac anTrenal sympathetic nerve activity. Anemic decerebration, cord transection at C4-C5, and severance of vagal or sympathetic cardiac nerves was done to identify the pathways and centers essential for these reflexes. Stretching the right atrium produced an acceleration of the heart and a definite increase in sympathetic nerve activity. Left atrial-stretch caused biphasic responses: an initial sympathetic nerve inhibition and slower heartbeat followed by sympathetic excitation and heart acceleration. The afferents responsible were carried mainly by the vagi; efferent neural control of the heart was mostly sympathetic. Since Bainbridge first discovered the phenomenon in 1915 (1), stretching the atria has been known to evoke reflex changes in heart rate, although reports of which reflex reactions are actually involved have been contradictory. In the last decade, cardiac reflexes have again attracted the attention of many physiologists and clinicians (2-5). Linden and his associates, using anesthetized dogs found that both left and right atrial stretch evoked acceleration of the heart, and that this acceleration is due solely to increased activity of cardiac sympathetic nerves (2). They also showed that the afferent pathways that evoke these reflexes are in the vagi, as originally stated by Bainbridge. Other investigators have reported that the heart rate is reduced by stretch of the left atrium (see refs. 3 and 6). It was also found that cardiac sympathetic nerves contained afferent tracts that could evoke reflex responses when the atria were stretched and it was claimed that the cardiac acceleration produced by stretching the atria was mainly mediated by sympathetic nerves and spinal reflex action (7). In a previous study (8), in which balloons were inserted and then inflated in the atria to cause stretching or in which sensitive areas were directly stretched, we found that stretching the right atrium produced only an acceleration of the heart and an increase in cardiac sympathetic nerve discharges. Stretching the left atrium, on the other hand, produced an early deceleration followed by a longer-lasting cardiac acceleration concurrent with a decrease and then an increase in cardiac sympathetic activity. Stretching the atria produced similar changes in activity of other sympathetic nerve trunks, such as the renal 2177 nerves. It was also found that somatosympathetic reflexes evoked by various somatic afferent nerves were affected by atrial stretch (8).Although there have been many morphological and physiological studies of atrial receptors and their afferent nerves (3, 9), the reflexes they evoke and the nerve centers involved have not been fully determined. The objective of the present study was to identify the centers, as well as the afferent and efferent pathways that are involved in reflex responses originating from the atria, and to analyze the individual roles of each. METHODS Twenty-four dogs of either sex ...

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“…Tachycardia observed in neonatal rabbit atria was not altered by propranolol or by reducing the passive tension, therefore the adrenergic beta mechanism and stretching of S-A nodes (12,13) are not involved. The rate was effectively slowed by acetylcholine (present study) and also by increase in K+, elevation of Ca++ or deprivation of Na+ in bathing media (unpublished data).…”

Section: Discussionmentioning

confidence: 88%

Age-Dependence of the Chronotropic Response to Noradrenaline, Acetylcholine and Transmural Stimulation in Isolated Rabbit Atria

Toda

Osumi

1976

Japanese Journal of Pharmacology

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Effects of localized stretch of the sinoatrial node region of the dog heart

Cited by 76 publications

References 0 publications

Length-dependent changes of pacemaker frequency in the isolated rabbit sinoatrial node.

Length-dependent changes of pacemaker frequency in the isolated rabbit sinoatrial node.

Centers involved in the autonomic reflex reactions originating from stretching of the atria.

Age-Dependence of the Chronotropic Response to Noradrenaline, Acetylcholine and Transmural Stimulation in Isolated Rabbit Atria

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