The carotid sinus baroreceptor reflex in conscious rabbits.

Faris, Irwin; Iannos, J.; Jamieson, G. G.; Ludbrook, John

doi:10.1113/jphysiol.1980.sp013083

Cited by 18 publications

(17 citation statements)

References 18 publications

(17 reference statements)

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“…However, there is evidence that in the rabbit the carotid chemoreceptors do not act tonically on the circulation (Chalmers et al, 1967a) and are not excited until the arterial pressure falls below 20 mm Hg (Ott et al, 1971;Faris et al, 1980), so that it is unlikely that effects attributed to baroreceptor input were confounded by the carotid chemoreceptor reflex. Intrapericardial procaine blocks afferents from the heart and not, for instance, those from the lungs (Arndt et al, 1981), but it also blocks the cardiac efferent nerves, so that it must be assumed that the calculated reflex effects on vascular resistance were unaffected by the abolition of changes in heart rate.…”

Section: Discussionmentioning

confidence: 98%

“…Intrapericardial procaine blocks afferents from the heart and not, for instance, those from the lungs (Arndt et al, 1981), but it also blocks the cardiac efferent nerves, so that it must be assumed that the calculated reflex effects on vascular resistance were unaffected by the abolition of changes in heart rate. This is a fair assumption in the case of the arterial baroreceptor reflex, since we have shown that-in conscious rabbits-the carotid sinus reflex controls arterial pressure by changing vascular resistance rather than cardiac output (Faris et al, 1981b), and that this control is unaffected by drugs that abolish changes in heart rate (Faris et al, 1980). The cardiac receptor reflex effects were examined after barodenervation, which of itself had abolished changes of heart rate as blood volume was altered (Fig.…”

Section: Discussionmentioning

confidence: 99%

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The role of cardiac receptor and arterial baroreceptor reflexes in control of the circulation during acute change of blood volume in the conscious rabbit.

Ludbrook¹,

Graham²

1984

Circulation Research

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We have studied overall reflex control of the circulation by the arterial baroreceptors and cardiac receptors during acute change of blood volume in seven conscious rabbits. A factorial experimental design allowed analysis of the direction, magnitude, and significance of the reflex effects of independent input from each set of receptors, and the reflex interactions when the inputs were combined. Right atrial pressure, arterial pressure, systemic vascular resistance, cardiac output, and heart rate were measured during acute, graded, isohemic change of blood volume over the range +/- 27%. This was done with both reflexes present, only the arterial baroreceptor reflex present (intrapericardial 2% procaine), only the cardiac receptor reflex present (surgical baroreceptor denervation), and with both reflexes absent. As blood volume was depleted, the arterial baroreceptor reflex independently increased systemic vascular resistance and sustained arterial pressure, but the cardiac receptor reflex had no significant independent or interactive effects. As blood volume was expanded, each reflex had an independent effect in decreasing systemic vascular resistance and preventing arterial pressure from rising, the cardiac receptor reflex being the more powerful. Their effect in combination on systemic vascular resistance and arterial pressure was only two-fifths of the sum of their independent effects, so that they interacted negatively. In combination, the reflexes supported right atrial pressure during blood loss, despite their negative interaction, but did not significantly affect the relation of cardiac output to blood volume change in either direction. Thus both reflexes have important actions in moderating the overall effects of acute blood volume changes in conscious rabbits, but these are markedly diminished by their interactions.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

The role of cardiac receptor and arterial baroreceptor reflexes in control of the circulation during acute change of blood volume in the conscious rabbit.

Ludbrook¹,

Graham²

1984

Circulation Research

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“…From this the maximum gain (G) of the reflex, and the upper and lower limiting values of HR (HRu, HR,) were estimated ( Fig. 2) (Faris et al, 1980b). The residual variance from the fitted curve was never more than 5% of the total variance.…”

Section: Analysis Of the Resultsmentioning

confidence: 99%

“…Six to 8 days before the second study both carotid sinuses were denervated and the aortic nerves divided, as described previously (Faris et al, 1980b).…”

Section: Surgical Proceduresmentioning

confidence: 99%

Comparison of the Reflex Effects of Arterial Baroreceptors and Cardiac Receptors on the Heart Rate of Conscious Rabbits

Ludbrook

1984

Clin Exp Pharma Physio

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The reflex effects on heart rate (HR) of presumptive cardiac receptors have been differentiated from those of the arterial baroreceptors in conscious rabbits by inflating cuffs on the ascending aorta, descending aorta, inferior vena cava and pulmonary artery. When the outflow from the right ventricle was progressively impeded the accompanying increase in HR was entirely explicable by unloading of the arterial baroreceptors. As the outflow from the left ventricle was progressively impeded there was an initial increase in HR due to unloading of the arterial baroreceptors, followed by a progressive decline. This decline was attributed to a reflex arising from vagally-innervated receptors in the left side of the heart. The threshold of this cardiac receptor-HR reflex occurred at a higher level of mean aortic pressure than that at which the effects of the arterial baroreceptors on HR were maximal. Cholinergic (vagal) efferent nerves were responsible for two-thirds of the decline in HR caused by the reflex. The properties of the cardiac receptor-HR reflex were altered by drugs that affect myocardial contractility. Isoprenaline raised the mean aortic pressure at which the threshold occurred, but lowered the corresponding level of left ventricular end-diastolic pressure. Propranolol virtually abolished the reflex, even though left ventricular end-diastolic pressure reached a high level. It is concluded that in the conscious rabbit the arterial baroreceptor reflexes normally prevent the threshold of the cardiac receptor-HR reflex from being attained.

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“…However, studies with the neck chamber have revealed (a) poor correlations between HR and BP effects on BR activation and deactivation (Faris et al, 1980;Ludbrook et al, 1980), and (b) that BR effects on BP may be independent of those on HR, since they are not reduced when HR is kept constant by atrial pacing or autonomic blockade. However, little information on that function in man was available until the development of the neck chamber technique.…”

Section: Measurement Of Arterial Pressure Changesmentioning

confidence: 99%

Antihypertensive Drugs and Baroreceptor Reflex Control of Heart Rate and Blood Pressure

Berdeaux

Giudicelli

1988

Fundamemntal Clinical Pharma

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Summary— The arterial baroreceptor reflex (BR; aortic and carotid sinus BR) and the cardiopulmonary BR are the most important reflexes acting as buffer systems for the maintenance of arterial pressure around a fixed physiologic value. They act as permanent inhibitory systems on the central cardiovascular structures and they can be either activated or deactivated by using selective techniques. During chronic hypertension there are structural alterations of the peripheral and/or central components of the BR that become «reset», with a shift in the function curve relating BR activity to blood pressure (BP) in the direction of higher pressure values. As a consequence of the hypertension‐induced resetting phenomenon, both the threshold pressure and sensitivity of BR are disturbed. However, if BR resetting during hypertension clearly decreases the sensitivity of BR control of heart rate (HR), BR control of peripheral resistance and arterial pressure as a whole is preserved and even increased when hypertension develops. Thus, this apparent discrepancy between BR control of HR and BP during hypertension demonstrates that evaluation of an antihypertensive therapy on reflex control of HR alone cannot predict what will happen to BR control of the whole cardiovascular system. Regarding BR control of HR, in contrast to the classical arteriolar vasodilators such as hydralazine and its derivatives, the majority of the modern antihypertensive drugs do not evoke reflex tachycardia in response to lowering of BP in normotensive or hypertensive subjects. Although the intrinsic pharmacologic mechanisms of action of these drugs on BR may be quite different (e.g., α1,‐or β‐adrenoreceptor blocking agents, converting enzyme inhibitors, certain calcium‐channel blockers of the phenyldihydropyridine group, and so on), they all shift in a parallel manner the set‐point of the BR response curve towards lower pressures, with no change in HR or R‐R interval. Generally, this resetting phenomenon occurs after several weeks or months of antihypertensive therapy, but it can also occur acutely (e.g. after IV injection) after administration of drugs such as prazosin or ketanserin. Finally, antihypertensive agents such as clonidine and methyldopa can simultaneously reset the BR and increase its sensitivity, thus leading to almost complete restoration of control of HR response despite the concomitant decrease in BP. Regarding BR control of blood pressure, only captopril and especially celiprolol (a β1‐adrenoreceptor blocking drug with vasodilating properties) are able to restore almost normal BR control of arterial pressure.

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The carotid sinus baroreceptor reflex in conscious rabbits.

Cited by 18 publications

References 18 publications

The role of cardiac receptor and arterial baroreceptor reflexes in control of the circulation during acute change of blood volume in the conscious rabbit.

The role of cardiac receptor and arterial baroreceptor reflexes in control of the circulation during acute change of blood volume in the conscious rabbit.

Comparison of the Reflex Effects of Arterial Baroreceptors and Cardiac Receptors on the Heart Rate of Conscious Rabbits

Antihypertensive Drugs and Baroreceptor Reflex Control of Heart Rate and Blood Pressure

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