Does the menstrual cycle influence the sensitivity of vagally mediated baroreflexes?

Cooke, William H.; Ludwig, David A.; Hogg, Paul; Eckberg, Dwain L.; Convertino, Víctor A.

doi:10.1042/cs20010326

Cited by 18 publications

(10 citation statements)

References 21 publications

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“…However, it should be noted that the gender comparisons in the present study were made between intact males and ovariectomized females with or without estrogen replacement. Other gonadal hormones such as progesterone and testosterone are also known to affect baroreflex function and cardiovascular ho- meostasis (6,8,11). The observations made with regard to gender differences in this study are limited to the contribution of estrogen alone.…”

Section: Discussionmentioning

confidence: 69%

Estrogen modulation of baroreflex function in conscious mice

Pamidimukkala

Taylor

Welshons

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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.-It has been suggested that estrogen modulates baroreflex regulation of autonomic function. The present study evaluated the effects of estrogen on baroreflex regulation of heart rate in response to changes in blood pressure with phenylephrine (PE), ANG II, and sodium nitroprusside (SNP) in a conscious mouse model. Males and ovariectomized females with (OvxEϩ) and without (OvxEϪ) estradiol replacement chronically implanted with arterial and venous catheters were used in these studies. The slope of the baroreflex bradycardic responses to PE was significantly facilitated in OvxEϩ females (Ϫ7.65 Ϯ 1.37) compared with OvxEϪ females (Ϫ4.5 Ϯ 0.4). Likewise, the slope of the baroreflex bradycardic responses to ANG II was significantly facilitated in OvxEϩ females (Ϫ7.97 Ϯ 1.06) compared with OvxEϪ females (Ϫ4.8 Ϯ 1.6). Reflex tachycardic responses to SNP were comparable in all the groups. Finally, in male mice, the slope of ANG II-induced baroreflex bradycardia (Ϫ5.17 Ϯ 0.95) was significantly less than that induced by PE (Ϫ8.50 Ϯ 0.92), but this ANG II-mediated attenuation of reflex bradycardia was not observed in the female mice. These data support the hypothesis that estrogen facilitates baroreflex function in female mice and suggest that ANG II-mediated acute blunting of baroreflex regulation of heart rate may be sex dependent. gender differences; autonomic regulation; cardiac baroreflexes EPIDEMIOLOGICAL STUDIES have shown that cardiovascular diseases such as hypertension and coronary heart disease are less common in premenopausal women compared with age-matched men (16,18,23,50). This innate protection in women against cardiovascular disease disappears with reproductive senescence or with removal of endogenous ovarian steroids (4,45,49).It is thought that estrogen may affect cardiovascular function at numerous levels including the vasculature, heart, and brain (36, 46). A potential mechanism by which estrogen provides cardioprotection in women is by acting at central cardiovascular regulatory centers to modulate autonomic regulation of the cardiovascular system. Hormone replacement therapy appears to have favorable effects on the cardiovascular autonomic regulation in postmenopausal women by improving baroreflex sensitivity and overall heart rate (HR) variability (19). Similar observations have also been made in male and ovariectomized female rats where estrogen replacement appears to improve baroreflex sensitivity via central mechanisms (32,43). However, to date, there have been no studies about the role of estrogen or gender in baroreflex control of HR in mice.ANG II is a potent circulatory peptide implicated in pathogenesis of hypertension. In addition to its peripheral vasoconstrictor effects, this peptide has been known to modulate reflex regulation of HR and sympathetic activity through circumventricular organs such as the area postrema (13, 37). In rabbits, dogs, and rats, acute increases in circulating ANG II blunt baroreflex regulation of HR (1,31,38,39). It is interesting to know if centrally mediated e...

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Section: Discussionmentioning

confidence: 69%

Estrogen modulation of baroreflex function in conscious mice

Pamidimukkala

Taylor

Welshons

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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“…The phase of the menstrual cycle might alter ventilatory baroreflex mechanisms. However, recent work suggests that neither the cardiovagal nor sympathetic baroreflexes are affected by menstrual cycle (9,15).…”

Section: Discussionmentioning

confidence: 99%

Ventilatory baroreflex sensitivity in humans is not modulated by chemoreflex activation

Stewart

Rivera²,

Clarke³

et al. 2011

American Journal of Physiology-Heart and Circulatory Physiology

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IL, Ocon AJ, Taneja I, Terilli C, Medow MS. Ventilatory baroreflex sensitivity in humans is not modulated by chemoreflex activation. Am J Physiol Heart Circ Physiol 300: H1492-H1500, 2011. First published February 11, 2011 doi:10.1152/ajpheart.01217.2010.-Increasing arterial blood pressure (AP) decreases ventilation, whereas decreasing AP increases ventilation in experimental animals. To determine whether a "ventilatory baroreflex" exists in humans, we studied 12 healthy subjects aged 18 -26 yr. Subjects underwent baroreflex unloading and reloading using intravenous bolus sodium nitroprusside (SNP) followed by phenylephrine ("Oxford maneuver") during the following "gas conditions:" room air, hypoxia (10% oxygen)-eucapnia, and 30% oxygen-hypercapnia to 55-60 Torr. Mean AP (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance (TPR), expiratory minute ventilation (V E), respiratory rate (RR), and tidal volume were measured. After achieving a stable baseline for gas conditions, we performed the Oxford maneuver. V E increased from 8.8 Ϯ 1.3 l/min in room air to 14.6 Ϯ 0.8 l/min during hypoxia and to 20.1 Ϯ 2.4 l/min during hypercapnia, primarily by increasing tidal volume. V E doubled during SNP. CO increased from 4.9 Ϯ .3 l/min in room air to 6.1 Ϯ .6 l/min during hypoxia and 6.4 Ϯ .4 l/min during hypercapnia with decreased TPR. HR increased for hypoxia and hypercapnia. Sigmoidal ventilatory baroreflex curves of V E versus MAP were prepared for each subject and each gas condition. Averaged curves for a given gas condition were obtained by averaging fits over all subjects. There were no significant differences in the average fitted slopes for different gas conditions, although the operating point varied with gas conditions. We conclude that rapid baroreflex unloading during the Oxford maneuver is a potent ventilatory stimulus in healthy volunteers. Tidal volume is primarily increased. Ventilatory baroreflex sensitivity is unaffected by chemoreflex activation, although the operating point is shifted with hypoxia and hypercapnia.baroreceptors; ventilation; blood pressure In intact animals (dogs) hyperpnea follows occlusion of the common carotid arteries; it is wholly reflex in origin because the effect is the same even though all branches of the carotids have been previously tied excepting only the lingual arteries, and because section of the sinus nerves completely abolishes the reaction.Carl F. Schmidt (45) DETECTION OF ARTERIAL BLOOD PRESSURE (AP) by the arterial baroreceptors causes changes in heart rate (HR), sympathetic vasoconstriction, adrenal function, and renal sympathetic activity (2, 5). Evidence primarily derived from animal experiments suggests that the carotid sinus baroreflex also affects respiratory function (7,26,45,48). Rapidly increasing blood pressure causes decreased ventilation, whereas decreasing blood pressure causes increased ventilation. While these ventilatory effects were at one time attributed to increased or decreased perfusion of the arterial chemoreceptors (26, 32), s...

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“…Nonetheless, the current data support earlier conclusions about attenuated cardiovagal baroreflex gain (1,38) and reduced heart rate responses to carotid baroreceptor stimulation (7) in women vs. men. Although cardiovagal and sympathetic baroreflex control may be affected by menstrual cycle (8,28), it is unclear whether this effect can overwhelm the overall difference between male and female orthostatic responses (36).…”

Section: Discussionmentioning

confidence: 99%

Forebrain neural patterns associated with sex differences in autonomic and cardiovascular function during baroreceptor unloading

Kimmerly¹,

Wong²,

Menon³

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Kimmerly DS, Wong S, Menon R, Shoemaker JK. Forebrain neural patterns associated with sex differences in autonomic and cardiovascular function during baroreceptor unloading. Am J Physiol Regul Integr Comp Physiol 292: R715-R722, 2007. First published July 6, 2006; doi:10.1152/ajpregu.00366.2006-Generally, women demonstrate smaller autonomic and cardiovascular reactions to stress, compared with men. The mechanism of this sex-dependent difference is unknown, although reduced baroreflex sensitivity may be involved. Recently, we identified a cortical network associated with autonomic cardiovascular responses to baroreceptor unloading in men. The current investigation examined whether differences in the neural activity patterns within this network were related to sex-related physiological responses to lower body negative pressure (LBNP,5,15, and 35 mmHg). Forebrain activity in healthy men and women (n ϭ 8 each) was measured using functional magnetic resonance imaging with blood oxygen level-dependent (BOLD) contrast. Stroke volume (SV), heart rate (HR), and muscle sympathetic nerve activity (MSNA) were collected on a separate day. Men had larger decreases in SV than women (P Ͻ 0.01) during 35 mmHg LBNP only. At 35 mmHg LBNP, HR increased more in males then females (9 Ϯ 1 beats/min vs. 4 Ϯ 1 beats/min, P Ͻ 0.05). Compared with women, increases in total MSNA were similar at 15 mmHg LBNP but greater during 35 mmHg LBNP in men [1,067 Ϯ 123 vs. 658 Ϯ 103 arbitrary units (au), P Ͻ 0.05]. BOLD signal changes (P Ͻ 0.005, uncorrected) were identified within discrete forebrain regions associated with these sex-specific HR and MSNA responses. Men had larger increases in BOLD signal within the right insula and dorsal anterior cingulate cortex than women. Furthermore, men demonstrated greater BOLD signal reductions in the right amygdala, left insula, ventral anterior cingulate, and ventral medial prefrontal cortex vs. women. The greater changes in forebrain activity in men vs. women may have contributed to the elevated HR and sympathetic responses observed in men during 35 mmHg LBNP. autonomic nervous system; baroreflex; microneurography; functional neuroimaging THE PHYSIOLOGICAL RESPONSES to a reduction in central blood volume involve baroreflex-mediated increases in heart rate (HR) and vascular resistance to adequately maintain arterial pressure and cerebral perfusion. Compared with men, reduced orthostatic tolerance has been observed in women (7,18), and this has been associated with differential (14, 36) autonomic and cardiovascular responses to baroreceptor unloading. In general, women respond to an orthostatic challenge with a greater HR increase, whereas men have larger increases in sympathetic vasoconstrictor activity and vascular resistance. The underlying mechanisms responsible for these varied responses are unclear but may be influenced by differences in the central processing and modulation of baroreceptor afferent information.Although the medulla oblongata remains the primary regulatory site of cardiovascular functi...

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Does the menstrual cycle influence the sensitivity of vagally mediated baroreflexes?

Cited by 18 publications

References 21 publications

Estrogen modulation of baroreflex function in conscious mice

Estrogen modulation of baroreflex function in conscious mice

Ventilatory baroreflex sensitivity in humans is not modulated by chemoreflex activation

Forebrain neural patterns associated with sex differences in autonomic and cardiovascular function during baroreceptor unloading

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