Sex differences in blood pressure control during 6° head-down tilt bed rest

Arzeno, Natalia M.; Stenger, Michael B.; Lee, Stuart M. C.; Ploutz‐Snyder, Robert; Platts, Steven H.

doi:10.1152/ajpheart.00391.2012

Cited by 21 publications

(21 citation statements)

References 63 publications

(104 reference statements)

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“…Experimental objectives were 1) to quantify the functional recruitment of Ah-type barosensory afferent fibers in the left ADN and 2) to determine what, if any, impact this additional pathway of myelinated barosensory afferents may have upon the frequency-dependent integration of the BRx. Collectively, our results support the hypothesis that low-threshold myelinated Ah-type aortic BR afferents substantially enhance the initial depressor response of the BRx in female compared with male rats and that these functional differences may account for, at least in part, the enhanced parasympathetic control of BP in females (3,44).…”

supporting

confidence: 83%

“…Differences in body size and contributing factors such as sex hormones and genetics do not explain the sex bias observed in OH between the sexes (12,30). Because orthostatic BP regulation in women occurs via parasympathetic withdrawal more than sympathetic activation (3,34), a BR-mediated increase in tonic resting parasympathetic activity could result in women requiring a larger increase in HR compared with men to achieve orthostatic stabilization.…”

Section: Discussionmentioning

confidence: 95%

“…Such BRx responses are dynamically modulated by the pressure-dependent discharge of arterial baroreceptor (BR) afferents that provide a continuous stream of systemic hemodynamic information to the central nervous system and are therefore essential to maintaining cardiovascular homeostasis (1,10,26). Recent and emerging studies document sex-related differences in many clinical assessments of integrated BRx function (3,6,8,13,16,36,37,44,57). Often, such differences are interpreted relative to sex-specific hormonal regulation of autonomic control (15,19,22,68).…”

mentioning

confidence: 99%

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An afferent explanation for sexual dimorphism in the aortic baroreflex of rat

Chavez

Glazebrook

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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Sex differences in baroreflex (BRx) function are well documented. Hormones likely contribute to this dimorphism, but many functional aspects remain unresolved. Our lab has been investigating a subset of vagal sensory neurons that constitute nearly 50% of the total population of myelinated aortic baroreceptors (BR) in female rats but less than 2% in male rats. Termed "Ah," this unique phenotype has many of the nonoverlapping electrophysiological properties and chemical sensitivities of both myelinated A-type and unmyelinated C-type BR afferents. In this study, we utilize three distinct experimental protocols to determine if Ah-type barosensory afferents underlie, at least in part, the sex-related differences in BRx function. Electron microscopy of the aortic depressor nerve (ADN) revealed that female rats have less myelin (P < 0.03) and a smaller fiber cross-sectional area (P < 0.05) per BR fiber than male rats. Electrical stimulation of the ADN evoked compound action potentials and nerve conduction profiles that were markedly different (P < 0.01, n = 7 females and n = 9 males). Selective activation of ADN myelinated fibers evoked a BRx-mediated depressor response that was 3-7 times greater in female (n = 16) than in male (n = 17) rats. Interestingly, the most striking hemodynamic difference was functionally dependent upon the rate of myelinated barosensory fiber activation. Only 5-10 Hz of stimulation evoked a rapid, 20- to 30-mmHg reduction in arterial pressure of female rats, whereas rates of 50 Hz or higher were required to elicit a comparable depressor response from male rats. Collectively, our experimental results are suggestive of an alternative myelinated baroreceptor afferent pathway in females that may account for, at least in part, the noted sex-related differences in autonomic control of cardiovascular function.

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supporting

confidence: 83%

Section: Discussionmentioning

confidence: 95%

mentioning

confidence: 99%

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An afferent explanation for sexual dimorphism in the aortic baroreflex of rat

Chavez

Glazebrook

et al. 2014

American Journal of Physiology-Heart and Circulatory Physiology

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“…Furthermore, applying different loading forces could reveal potential intensity-driven modulations. While previous experiments have already considered some of these aspects in orthostatic conditions [40,47,4,9,2], the results may not directly translate to HDT as this condition is characterized by increased central blood volume and reduced venous pooling when compared to upright posture.…”

Section: Discussionmentioning

confidence: 93%

Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Alessandro

Tafreshi

Riener

2018

Preprint

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The physiological processes underlying hemodynamic homeostasis can be modulated by muscle activity and gravitational loading. The effects of antigravity muscle activity on cardiovascular regulation has been observed during orthostatic stress. Here, we evaluated such effects during head-down tilt (HDT). In this posture, the gravitational gradient along the body is different than in upright position, leading to increased central blood volume and reduced venous pooling. We compared the cardiovascular signals obtained with and without antigravity muscle loading during HDT in healthy human subjects, both at rest and during recovery from leg-press exercises. Further, we compared such cardiovascular responses to those obtained during upright position. We found that loading the antigravity muscles during HDT at rest led to significantly higher values of arterial blood pressure than without muscle loading, and restored systolic values to those observed during upright posture. Maintaining muscle loading post-exercise altered the short-term cardiovascular responses, but not the values of the signals five minutes after the exercise. These results demonstrate that antigravity muscle activity modulates cardiovascular regulation during HDT. This modulation should therefore be considered when interpreting cardiovascular responses to conditions that affect both gravity loading and muscle activity, for example bed rest or microgravity.

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“…The worldwide prevalence of hypertension between 2000 and 2025 was predicted to increase by 9% in males and 13% in females 2. In many low-income and middle-income countries, hypertension has been considered a major public health concern.…”

Section: Introductionmentioning

confidence: 99%

Sex differences in antihypertensive drug use and blood pressure control

Wang

Jiang

Sharma

et al. 2019

Postgraduate Medical Journal

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BackgroundHypertension is the most important modifiable cardiovascular risk factor. Epidemiological studies have shown the benefits of lowering blood pressure (BP), but BP control is a major challenge. Furthermore, there are significant sex differences in antihypertensive drug use and BP control. This study examined sex differences in antihypertensive drug use and BP control, with the aim of reducing the complications of hypertension and improving quality of life.MethodsThe study was performed in our outpatient hypertension clinic, and included 1529 patients without secondary hypertension or comorbidities. The study, investigated BP control rates and patterns of antihypertensive drug use in male and female. All data were collected using structured questionnaires and patient measurements.ResultsThe study included 713 males and 816 females in this study. Fewer females had hypertension in the younger age group (16.2% vs 11.6%; p>0.05), but this difference disappeared in middle-aged (47.8% vs 49.9 %; p<0.05) and elderly age groups (36.0% vs 38.5%; p<0.05). BP control rates differed between males and females (35.6% in male, 31.9% in female, p<0.01). There was an overall difference in BP control rates between males and females (35.6% in males, 31.9% in females, p<0.01). In this aged 18–44 years, angiotensin converting enzyme inhibitors (ACEIs) showed the best control rate in males, while calcium channel blockers (CCBs) were least effective (61.5% with ACEIs, 28.6% with CCBs; p<0.05). In this aged 45–64 years, diuretics (DUs) showed the best control rate in females, while CCBs were least effective (47.5% with DUs, 28.3% with CCBs; p<0.05).ConclusionsSex plays an important role in BP control. In those aged 18–44 years, males using ACEIs showed best control rates. In those aged 45–64 years, females using DUs showed best control rates. Our study provides a basis with the selection of antihypertensive drugs according to sex and age.

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Sex differences in blood pressure control during 6° head-down tilt bed rest

Cited by 21 publications

References 63 publications

An afferent explanation for sexual dimorphism in the aortic baroreflex of rat

An afferent explanation for sexual dimorphism in the aortic baroreflex of rat

Cardiovascular responses to antigravity muscle loading during head-down tilt at rest and after dynamic exercises

Sex differences in antihypertensive drug use and blood pressure control

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