Changes in cardiac output and total peripheral resistance during the carotid sinus baroreceptor reflex in the pregnant rabbit.

Humphreys, P. W.; Joels, N.

doi:10.1113/jphysiol.1977.sp012033

Cited by 18 publications

(18 citation statements)

References 8 publications

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“…The present study examines the possibility that the lower total peripheral resistance at all levels of carotid sinus pressure noted by Humphreys & Joels (1977) derives in part from changes induced by pregnancy in vascular beds other than those directly concerned with reproduction. The circulation to the hind-limb musculature is an example of such a vascular bed.…”

Section: P W Humphreys and N Joelsmentioning

confidence: 99%

“…A comparison of the carotid sinus baroreceptor reflex in pregnant and non-pregnant rabbits has shown that, at all levels of carotid sinus pressure, total peripheral resistance is lower in pregnant rabbits (Humphreys & Joels, 1977); at sinus pressures between 75 and 110 mmHg, which encompassed the range of arterial pressures in the majority of the rabbits, this reduction was in the region of 20-25 %, and was accompanied by a similar reduction in blood pressure.…”

Section: Introductionmentioning

confidence: 99%

“…1). The technique for vascular isolation and perfusion has been fully described elsewhere (Humphreys & Joels, 1977). The left carotid sinus nerve was cut, and both aortic nerves were divided close to their junctions with the superior laryngeal nerves to minimize reflex baroreceptor effects originating from regions other than the isolated carotid sinus.…”

Section: Isolation Of the Carotid Sinusmentioning

confidence: 99%

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Reflex response of the rabbit hind‐limb muscle vascular bed to baroreceptor stimulation and its modification by pregnancy.

Humphreys¹,

Joels²

1982

The Journal of Physiology

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SUMMARY1. The pressure-flow relationship of the blood-perfused skinned hind limb has been compared in primigravid pregnant and virgin non-pregnant rabbits while pressure within the vascularly isolated carotid sinus was held at a series ofnon-pulsatile values.2. At each level of sinus pressure the slope of the pressure-flow relationship was steeper in the pregnant animals. Thus, at all but the very lowest flows, the same flow was achieved at a lower perfusion pressure in the pregnant rabbits.3. When hind-limb vascular resistance at constant flow was plotted against carotid sinus pressure it could be seen that at each level of sinus pressure vascular resistance was less in the pregnant rabbits.4. The reflex responses of the hind-limb bed to changes in sinus pressure were compared in pregnant and non-pregnant animals; there was little difference in the threshold and saturation values of carotid sinus pressure. There seemed to be a small reduction in the range and gain of the reflex in the pregnant group but this was not statistically significant. 5. We have previously shown total peripheral resistance in the pregnant rabbit to be less than that in the non-pregnant rabbit at the same level of sinus pressure. The lower hind-limb vascular resistance of the pregnant rabbit at any given sinus pressure must contribute to this reduced total peripheral resistance.

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Section: P W Humphreys and N Joelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Isolation Of the Carotid Sinusmentioning

confidence: 99%

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Reflex response of the rabbit hind‐limb muscle vascular bed to baroreceptor stimulation and its modification by pregnancy.

Humphreys¹,

Joels²

1982

The Journal of Physiology

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“…This change was first noted by Humphreys and Joels (97,98) in an extensive series of studies in anesthetized pregnant rabbits, in which reductions in carotid sinus pressure failed to elicit normal increases in arterial pressure and peripheral vascular resistance. Since then, arterial baroreflex impairment has been documented in several species studied in the conscious state, including dogs (23), rats (24,124), rabbits (21,97,162), goats (152), sheep (104,123), and humans (16,79,122,164,175,193).…”

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Pregnancy and the endocrine regulation of the baroreceptor reflex

Brooks

Dampney

Heesch

2010

American Journal of Physiology-Regulatory, Integrative and Comp

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-The purpose of this review is to delineate the general features of endocrine regulation of the baroreceptor reflex, as well as specific contributions during pregnancy. In contrast to the programmed changes in baroreflex function that occur in situations initiated by central command (e.g., exercise or stress), the complex endocrine milieu often associated with physiological and pathophysiological states can influence the central baroreflex neuronal circuitry via multiple sites and mechanisms, thereby producing varied changes in baroreflex function. During pregnancy, baroreflex gain is markedly attenuated, and at least two hormonal mechanisms contribute, each at different brain sites: increased levels of the neurosteroid 3␣-hydroxydihydroprogesterone (3␣-OH-DHP), acting in the rostral ventrolateral medulla (RVLM), and reduced actions of insulin in the forebrain. 3␣-OH-DHP appears to potentiate baroreflex-independent GABAergic inhibition of premotor neurons in the RVLM, which decreases the range of sympathetic nerve activity that can be elicited by changes in arterial pressure. In contrast, reductions in the levels or actions of insulin in the brain blunt baroreflex efferent responses to increments or decrements in arterial pressure. Although plasma levels of angiotensin II are increased in pregnancy, this is not responsible for the reduction in baroreflex gain, although it may contribute to the increased level of sympathetic nerve activity in this condition. How these different hormonal effects are integrated within the brain, as well as possible interactions with additional potential neuromodulators that influence baroreflex function during pregnancy and other physiological and pathophysiological states, remains to be clearly delineated.3␣-hydroxy-dihydroprogesterone; angiotensin II; insulin; paraventricular nucleus of the hypothalamus NORMAL PREGNANCY is characterized by profound changes in fluid and electrolyte balance and blood pressure regulation. Blood volume and cardiac output increase by 30 -50%, but arterial pressure falls due to even greater decreases in systemic vascular resistance (120,138,189). These hemodynamic alterations are evident early in pregnancy, precede the increases in uterine blood flow, and are sustained until parturition (127,138,189). Considerable data implicate increases in relaxin and nitric oxide (NO) in the systemic vasodilation induced by pregnancy (20,127,128,177,196). In addition, peripheral vascular sensitivity to circulating vasoconstrictors including vasopressin, angiotensin II (ANG II), and norepinephrine (NE) is decreased (50,71,154).Unlike the hemodynamic changes, which likely subserve adequate fetal development, an adverse consequence of normal pregnancy is a marked impairment of the arterial baroreceptor reflex. This change was first noted by Humphreys and Joels (97,98) in an extensive series of studies in anesthetized pregnant rabbits, in which reductions in carotid sinus pressure failed to elicit normal increases in arterial pressure and peripheral vascular resistanc...

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“…Cardiac output was measured at intervals by thermal dilution as described previously (Humphreys & Joels, 1977 a). 0-6 ml 0-9 % NaCl at room temperature was injected from a calibrated syringe into the right atrium via a catheter passed through the right external jugular vein until its tip lay just proximal to the entry of the superior vena cava into the right atrium.…”

Section: Methodsmentioning

confidence: 99%

Arterial pressure maintenance after haemorrhage in the pregnant rabbit.

Humphreys¹,

Joels²

1985

The Journal of Physiology

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The changes in arterial blood pressure and cardiac output following rapid removal of 10% of the blood volume have been compared in non‐pregnant and pregnant anaesthetized rabbits close to term (28 or 29 days gestation). Immediately after the end of haemorrhage the fall in arterial pressure was greater in the pregnant group (27.7 vs. 17.8 mmHg), but as recovery proceeded the difference diminished and by the tenth minute the reduction from pre‐haemorrhage levels was similar in pregnant and non‐pregnant rabbits. Cardiac output fell by about 30% in both groups and increased only very slightly during the ensuing 10 min. 1 h after section of the carotid sinus and aortic nerves the haemorrhage was repeated. The fall in arterial pressure in the non‐pregnant rabbits was now more than doubled (47.2 vs. 17.8 mmHg). By contrast it was little changed in the pregnant rabbits (32.0 vs. 27.7 mmHg). It is concluded that pregnancy diminishes the role of the baroreceptor reflexes in the response of the rabbit to haemorrhage. Other mechanisms, such as an increased compliance of the resistance vessels and/or a more effective chemically mediated vasoconstriction, probably become of more importance to the maintenance of arterial pressure.

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Changes in cardiac output and total peripheral resistance during the carotid sinus baroreceptor reflex in the pregnant rabbit.

Cited by 18 publications

References 8 publications

Reflex response of the rabbit hind‐limb muscle vascular bed to baroreceptor stimulation and its modification by pregnancy.

Reflex response of the rabbit hind‐limb muscle vascular bed to baroreceptor stimulation and its modification by pregnancy.

Pregnancy and the endocrine regulation of the baroreceptor reflex

Arterial pressure maintenance after haemorrhage in the pregnant rabbit.

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