Modulation of arterial baroreflex dynamic response during mild orthostatic stress in humans

Ichinose, Masashi; Saito, Mitsuru; Kitano, Asami; Hayashi, Keiji; Kondo, Narihiko; Nishiyasu, Takeshi

doi:10.1113/jphysiol.2003.057133

Cited by 28 publications

(25 citation statements)

References 41 publications

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“…Furthermore, previous studies have demonstrated an increase of sympathetic baroreflex sensitivity during mild levels of LBNP (11,15). The increased sympathetic baroreflex sensitivities observed during LBNP in the present study and others (11,15) are suggestive that alterations of sympathetic baroreflex sensitivity during orthostatic stress are important in the maintenance of orthostatic tolerance. Our results indicate that such adjustments are not different between the EF and ML phases of the menstrual cycle.…”

Section: Discussionsupporting

confidence: 61%

“…Nevertheless, our data indicate an increase of sympathetic baroreflex sensitivity during progressive LBNP that was not observed by Ichinose et al (10). Furthermore, previous studies have demonstrated an increase of sympathetic baroreflex sensitivity during mild levels of LBNP (11,15). The increased sympathetic baroreflex sensitivities observed during LBNP in the present study and others (11,15) are suggestive that alterations of sympathetic baroreflex sensitivity during orthostatic stress are important in the maintenance of orthostatic tolerance.…”

Section: Discussionsupporting

confidence: 35%

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Menstrual cycle alters sympathetic neural responses to orthostatic stress in young, eumenorrheic women

Carter

Lawrence²,

Klein³

2009

American Journal of Physiology-Endocrinology and Metabolism

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Carter JR, Lawrence JE, Klein JC. Menstrual cycle alters sympathetic neural responses to orthostatic stress in young, eumenorrheic women. Am J Physiol Endocrinol Metab 297: E85-E91, 2009. First published April 28, 2009 doi:10.1152/ajpendo.00019.2009.-Sympathetic baroreflex sensitivity (BRS) and muscle sympathetic nerve activity (MSNA) responses during early follicular (EF) and midluteal (ML) phases of the menstrual cycle are controversial. We hypothesize an augmented sympathetic BRS and MSNA response to orthostatic stress during the ML phase of the menstrual cycle. MSNA, mean arterial pressure (MAP), and heart rate (HR) were recorded during progressive lower body negative pressure (LBNP) (Ϫ5, Ϫ10, Ϫ15, Ϫ20, Ϫ30, and Ϫ40 mmHg; 3 min/stage) in 13 healthy, eumenorrheic women (age 21 Ϯ 1 yr). Sympathetic BRS was assessed by examining relations between spontaneous fluctuations of diastolic arterial pressure and MSNA at rest and during progressive LBNP. Plasma estradiol (42 Ϯ 6 vs. 112 Ϯ 12 pg/ml; P Ͻ 0.01) and progesterone (2 Ϯ 0 vs. 10 Ϯ 2 ng/ml; P Ͻ 0.04) were elevated during the ML phase. Resting MSNA (8 Ϯ 1 vs. 11 Ϯ 1 bursts/min), MAP (79 Ϯ 2 vs. 78 Ϯ 2 mmHg), and HR (58 Ϯ 2 vs. 60 Ϯ 2 beats/min) were not different during EF and ML phases. MSNA and HR increased during progressive LBNP (P Ͻ 0.001), and the increases in MSNA burst frequency (bursts/min) and HR were similar during both phases. In contrast, increases in total MSNA (arbitrary units) during progressive LBNP were augmented during the ML phase (P Ͻ 0.04), but this response does not appear to be linked to differences in sympathetic BRS. Progressive LBNP did not change MAP during either phase. Our results demonstrate an augmentation of the MSNA response to progressive LBNP during the ML phase of the menstrual cycle. These findings suggest that hormonal fluctuations of eumenorrheic women may influence sympathoexcitation during an orthostatic challenge, but not through sympathetic baroreflex-mediated pathways. muscle sympathetic nerve activity; arterial blood pressure; lower body negative pressure; baroreflex; estrogen EVIDENCE SUGGESTS THAT ORTHOSTATIC intolerance is more prevalent in women compared with men (3,5,7,19,(21)(22)(23). The mechanisms responsible for this apparent sex difference are presently unclear, but altered patterns of sympathoexcitation have been suggested. Shoemaker et al. (22) reported a blunted muscle sympathetic nerve activity (MSNA) response to orthostatic stress in women compared with men, suggesting MSNA responses to an orthostatic challenge may contribute to the higher incidence of orthostatic intolerance in women. In contrast, Fu et al. (9) recently reported that sex did not affect MSNA responses to an orthostatic challenge. The influence of sex on MSNA responses to orthostatic stress remains debatable.Shoemaker et al. (22) and Fu et al. (8) did not control for menstrual phase in their female subjects; thus, it is possible that differences between these two studies were due to hormonal fluctuations associated with the menstrua...

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Section: Discussionsupporting

confidence: 61%

Section: Discussionsupporting

confidence: 35%

Menstrual cycle alters sympathetic neural responses to orthostatic stress in young, eumenorrheic women

Carter

Lawrence²,

Klein³

2009

American Journal of Physiology-Endocrinology and Metabolism

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“…Consistent with prior studies (Crandall 2000;Ichinose et al 2004;Ogoh et al 2002Ogoh et al , 2003, the response of MAP to NP or NS was elicited slowly compared to that of HR (Figs. 2, 3, 4, 5).…”

Section: Discussionsupporting

confidence: 89%

Whole-body heating slows carotid baroreflex response in human subjects

Yamazaki

Sone

2005

Eur J Appl Physiol

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Heat stress increases sympathetic activity and decreases parasympathetic activity to the heart. To test the hypothesis that carotid baroreflex responses of heart rate (HR) and systemic blood pressure become slowed with altered autonomic nerve activities during whole-body heat stress, we determined changes in HR and mean arterial pressure (MAP) in response to approximately 5 s of 40 mmHg neck pressure (NP) and of -65 mmHg neck suction (NS) in normothermia and during whole-body heating produced by a hot water-perfused suit. The NP and NS stimuli were triggered by R waves of an ECG during held expiration in the supine position. Whole-body heating did not alter the onset time of the HR and MAP responses during NP and NS. Whole-body heating significantly increased the time from onset of the HR response until peak of the response during NP (2.53 +/- 0.33 s in normothermia and 3.46 +/- 0.28 s during heating, P<0.05) and NS (1.20 +/- 0.23 s and 2.24 +/- 0.29 s, P<0.05). Whole-body heating significantly increased the time from onset of the MAP response until peak of the response during NP (4.31+/-0.46 s in normothermia, 6.67 +/- 0.56 s during heating, P<0.05) but not during NS (5.06 +/- 0.47 s and 4.50 +/- 0.60 s). These findings suggest that heat stress prolongs the response time of carotid-cardiac and carotid-vasomotor baroreflexes.

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“…The larger influence of arterial baroreflex on blood pressure maintenance during long-duration HDBR, even in the absence of evidence pointing to its enhancement, and the simultaneous reduction of the role of cardiopulmonary baroreflex can contribute toward the interpretation of the occurrence of syncope in individuals who have completed HDBR (20), or in astronauts upon return to earth. In addition, these conclusions could also be of importance in interpreting the pathology of subjects who are prone to syncope and orthostatic intolerance.…”

Section: Perspectives and Significancementioning

confidence: 99%

Short-term variability of blood pressure: effects of lower-body negative pressure and long-duration bed rest

Aletti

Ferrario

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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(LBNP) has been utilized to selectively unload cardiopulmonary baroreceptors, but there is evidence that arterial baroreceptors can be transiently unloaded after the onset of mild LBNP. In this paper, a black box mathematical model for the prediction of diastolic blood pressure (DBP) variability from multiple inputs (systolic blood pressure, R-R interval duration, and central venous pressure) was applied to interpret the dynamics of blood pressure maintenance under the challenge of LBNP and in long-duration, headdown bed rest (HDBR). Hemodynamic recordings from seven participants in the WISE (Women's International Space Simulation for Exploration) Study collected during an experiment of incremental LBNP (Ϫ10 mmHg, Ϫ20 mmHg, Ϫ30 mmHg) were analyzed before and on day 50 of a 60-day-long HDBR campaign. Autoregressive spectral analysis focused on low-frequency (LF, ϳ0.1 Hz) oscillations of DBP, which are related to fluctuations in vascular resistance due to sympathetic and baroreflex regulation of vasomotor tone. The arterial baroreflex-related component explained 49 Ϯ 13% of LF variability of DBP in spontaneous conditions, and 89 Ϯ 9% (P Ͻ 0.05) on day 50 of HDBR, while the cardiopulmonary baroreflex component explained 17 Ϯ 9% and 12 Ϯ 4%, respectively. The arterial baroreflexrelated variability was significantly increased in bed rest also for LBNP equal to Ϫ20 and Ϫ30 mmHg. The proposed technique provided a model interpretation of the proportional effect of arterial baroreflex vs. cardiopulmonary baroreflex-mediated components of blood pressure control and showed that arterial baroreflex was the main player in the mediation of DBP variability. Data during bed rest suggested that cardiopulmonary baroreflex-related effects are blunted and that blood pressure maintenance in the presence of an orthostatic stimulus relies mostly on arterial control. arterial blood pressure; variability; baroreflex; lower body negative pressure; bed rest MILD OR NONHYPOTENSIVE LOWER body negative pressure (LBNP; Ϫ20 mmHg Ͻ LBNP Ͻ 0 mmHg) has been used to selectively unload cardiopulmonary baroreceptors (25,44,46,50). However, straightforward observations of the time course of mean arterial pressure (MAP) following rapid onset of mild LBNP (17, 18) evidenced a transient decrease followed by a recovery of pre-LBNP onset values, suggesting that arterial baroreceptors are affected by mild LBNP as well. More detailed analyses of such transient decreases of MAP in LBNP (13) showed that also systolic blood pressure (SBP) and diastolic blood pressure (DBP) fall and are restored within ϳ15 heart beats, confirming a direct involvement of arterial baroreflex, consistently with previous reports (23,35,45). However, to our knowledge, the quantification of the relative dynamic contribution of arterial and cardiopulmonary baroreflex has not been addressed yet. Fu et al. (13) concluded that arterial baroreflex is engaged and unloaded by mild LBNP, but they could not determine the proportional influence of cardiopulmonary vs. arterial baroreflex on t...

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Modulation of arterial baroreflex dynamic response during mild orthostatic stress in humans

Cited by 28 publications

References 41 publications

Menstrual cycle alters sympathetic neural responses to orthostatic stress in young, eumenorrheic women

Menstrual cycle alters sympathetic neural responses to orthostatic stress in young, eumenorrheic women

Whole-body heating slows carotid baroreflex response in human subjects

Short-term variability of blood pressure: effects of lower-body negative pressure and long-duration bed rest

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