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Experimental Physiology Oct 2023What is the topic of this review? We review barosensory vessel mechanics and their role in blood pressure regulation across the lifespan. What advances does it... (Review)
Review
NEW FINDINGS
What is the topic of this review? We review barosensory vessel mechanics and their role in blood pressure regulation across the lifespan. What advances does it highlight? In young normotensive men, aortic unloading mechanics contribute to the resting operating point of the vascular sympathetic baroreflex; however, with advancing age, this contribution is removed. This suggests that barosensory vessel unloading mechanics are not driving the well-documented age-related increase in resting muscle sympathetic nerve activity.
ABSTRACT
An age-associated increase in arterial blood pressure is evident for apparently healthy humans. This is frequently attributed to stiffening of the central arteries and a concurrent increase in sympathetic outflow, potentially mediated by a reduced ability of the baroreceptive vessels to distend. This is supported, in part, by a reduced mechanical component of the vascular sympathetic baroreflex (i.e., a reduction in distension for a given pressure). Previous characterization of the mechanical component has assessed only carotid artery distension; however, evidence suggests that both the aortic and carotid baroreflexes are integral to blood pressure regulation. In addition, given that baroreceptors are located in the vessel wall, the change in wall tension, comprising diameter, pressure and vessel wall thickness, and the mechanics of this change might provide a better index of the baroreceptor stimulus than the previous method used to characterize the mechanical component that relies on diameter alone. This brief review summarizes the data using this new method of assessing barosensory vessel mechanics and their influence on the vascular sympathetic baroreflex across the lifespan.
Topics: Male; Humans; Baroreflex; Blood Pressure; Pressoreceptors; Carotid Arteries; Sympathetic Nervous System; Homeostasis; Heart Rate
PubMed: 37031381
DOI: 10.1113/EP089686 -
Journal of Hypertension Jul 2023The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously...
BACKGROUND
The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously demonstrated functional differences in the central processing of the left versus right aortic baroreceptor afferent input. However, it is unknown if lateralization in aortic baroreflex function remains evident during hypertension.
METHOD
We therefore, investigated the effects of laterality on the expression of baroreflex-driven cardiovascular reflexes in a genetic model of essential hypertension, the spontaneously hypertensive rat (SHR). Anesthetized male SHRs (total n = 9) were instrumented for left, right, and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, and 0.4 mA for 20 s) and measurement of mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR), and femoral vascular resistance (FVR).
RESULTS
Left right, and bilateral ADN stimulation evoked frequency-dependent decreases in MAP, HR, MVR, and FVR. Left and bilateral ADN stimulation evoked greater reflex reductions in MAP, HR, MVR, and FVR compared with right-sided stimulation. Reflex bradycardia to bilateral stimulation was larger relative to both left-sided and right-sided stimulation. Reflex depressor and vascular resistance responses to bilateral stimulation mimicked those of the left-sided stimulation. These data indicate a left-side dominance in the central integration of aortic baroreceptor afferent input. Furthermore, reflex summation due to bilateral stimulation is only evident on the reflex bradycardic response, and does not drive further reductions in BP, suggesting that reflex depressor responses in the SHRs are primarily driven by changes in vascular resistance.
CONCLUSION
Together, these results indicate that lateralization in aortic baroreflex function is not only evident under normotensive conditions but also extends to hypertensive conditions.
Topics: Rats; Animals; Male; Rats, Inbred SHR; Pressoreceptors; Electric Stimulation; Blood Pressure; Baroreflex; Hypertension; Heart Rate; Aorta
PubMed: 37074354
DOI: 10.1097/HJH.0000000000003448 -
The Journal of Maternal-fetal &... Dec 2023Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on...
OBJECTIVE
Baroreflex is a regulatory mechanism that slows the fetal heart rate. This study aimed to investigate the effects of lipopolysaccharide (LPS)-induced endotoxemia on fetal baroreceptor sensitivity in preterm fetal sheep.
METHODS
The changes in fetal baroreceptor sensitivity were measured in seven chronically instrumented preterm fetal sheep. Fetal baroreceptor sensitivity was measured in three phases: (A) control phase, defined as the 24 h before the first injection of LPS; (B) acute phase, defined as the 24 h between the first and second injections of LPS; and (C) fetal acidosis phase, defined as the time from the second LPS injection until intrauterine fetal death. Histological examinations of the fetal membrane and umbilical cord were also conducted.
RESULTS
Each fetus developed metabolic acidosis after the second injection of LPS. The fetuses died 24.7 (SD = 6.1) hours after the second injection of LPS. Both the umbilical cord and fetal membranes showed histological evidence of severe inflammation. In total, 163 fetal baroreceptor measurements were performed in this experiment (A, = 77 times; B, = 60 times; C, = 26 times). Fetal baroreceptor sensitivity showed significant differences in all three phases (A: 2.7 [SD = 0.2]; B: 2.5 [SD = 0.2]; and C: 1.5 [SD = 0.2]). Post hoc tests showed that baroreceptor sensitivity in the acidosis phase had decreased significantly compared to that in the control and acute phases (<.001 and =.002, respectively).
CONCLUSIONS
Fetal baroreceptor sensitivity decreased during fetal acidosis induced by LPSs.
Topics: Pregnancy; Female; Humans; Sheep; Animals; Lipopolysaccharides; Pressoreceptors; Fetus; Inflammation; Fetal Diseases; Acidosis; Heart Rate, Fetal
PubMed: 36443245
DOI: 10.1080/14767058.2022.2150392 -
The Journal of Physiological Sciences :... Jun 2023This study investigated effects of experimental baroreceptor stimulation on bilateral blood flow velocities in the anterior and middle cerebral arteries (ACA and MCA)...
This study investigated effects of experimental baroreceptor stimulation on bilateral blood flow velocities in the anterior and middle cerebral arteries (ACA and MCA) using functional transcranial Doppler sonography. Carotid baroreceptors were stimulated by neck suction in 33 healthy participants. Therefore, negative pressure (- 50 mmHg) was applied; neck pressure (+ 10 mmHg) was used as a control condition. Heart rate (HR) and blood pressure (BP) were also continuously recorded. Neck suction led to reductions in bilateral ACA and MCA blood flow velocities, which accompanied the expected HR and BP decreases; HR and BP decreases correlated positively with the ACA flow velocity decline. The observations suggest reduction of blood flow in the perfusion territories of the ACA and MCA during baroreceptor stimulation. Baroreceptor-related HR and BP decreases may contribute to the cerebral blood flow decline. The findings underline the interaction between peripheral and cerebral hemodynamic regulation in autoregulatory control of cerebral perfusion.
Topics: Humans; Blood Flow Velocity; Pressoreceptors; Middle Cerebral Artery; Blood Pressure; Heart Rate
PubMed: 37312034
DOI: 10.1186/s12576-023-00871-7 -
Journal of Atherosclerosis and... Apr 2024The carotid sinuses and aortic arch are baroreceptor-resident arteries (BRAs) and atherosclerosis-susceptible sites of brain-supplying arteries, which would impair...
Evaluating Total Atherosclerosis Burden of Baroreceptor-Resident Arteries after Ischemic Cerebrovascular Disease for Identifying Patients with Heavy Coronary Atherosclerosis Burden.
AIM
The carotid sinuses and aortic arch are baroreceptor-resident arteries (BRAs) and atherosclerosis-susceptible sites of brain-supplying arteries, which would impair baroreflex-mediated blood pressure (BP) regulation and prompt coronary atherosclerosis. We sought to determine the relationship between total atherosclerosis burden (TAB) of BRAs and coronary atherosclerosis burden (AB) in patients with ischemic cerebrovascular disease (ICVD) and explore the potential contribution of BP profiles to this relationship.
METHODS
In this cross-sectional analysis of patients with ICVD who simultaneously undertook computed tomography angiography and 24-hour ambulatory BP monitoring, TAB of BRAs was scored based on the atherosclerotic vessel circumference ratio of the carotid sinuses and aortic arch, while the ABs of the intracranial, cervical, aortic, and coronary arteries were scored based on stenosis severity and plaque complexity as routine.
RESULTS
Among the 230 patients analyzed, coronary AB was significantly correlated with TAB of BRAs, independently of, and more tightly than the ABs of the intracranial, cervical, and aortic arteries, and the stenosis- and complexity-based AB of BRA-located arteries (bilateral common and extracranial internal carotid arteries and aortic arch). Both coronary AB and TAB of BRAs were negatively associated with the night-to-day BP dipping ratios, which was quite different from the relationship between intracranial AB and 24-hour BP characteristics. These findings were also true for patients with ICVD without a history of coronary artery disease.
CONCLUSION
Evaluating TAB of BRAs might provide a new link between atherosclerosis of brain- and heart-supplying arteries, connected partially by BP circadian rhythm. It might facilitate identifying patients with ICVD with heavy coronary AB and comprehensively managing vascular risk.
Topics: Humans; Coronary Artery Disease; Stroke; Constriction, Pathologic; Pressoreceptors; Cross-Sectional Studies; Risk Factors; Atherosclerosis; Arteries
PubMed: 37866928
DOI: 10.5551/jat.64457 -
The Journal of Physiological Sciences :... Mar 2024The purpose of this study was to clarify sex differences in the inhibition of sympathetic vasomotor outflow which is caused by the loading of cardiopulmonary...
The purpose of this study was to clarify sex differences in the inhibition of sympathetic vasomotor outflow which is caused by the loading of cardiopulmonary baroreceptors. Ten young males and ten age-matched females participated. The participants underwent a passive leg raising (PLR) test wherein they were positioned supine (baseline, 0º), and their lower limbs were lifted passively at 10º, 20º, 30º, and 40º. Each angle lasted for 3 min. Muscle sympathetic nerve activity (MSNA) was recorded via microneurography of the left radial nerve. Baseline MSNA was lower in females compared to males. MSNA burst frequency was decreased during the PLR in both males (- 6.2 ± 0.4 bursts/min at 40º) and females (- 6.5 ± 0.4 bursts/min at 40º), but no significant difference was detected between the two groups (P = 0.61). These results suggest that sex has minimal influence on the inhibition of sympathetic vasomotor outflow during the loading of cardiopulmonary baroreceptors in young individuals.
Topics: Humans; Male; Female; Leg; Muscle, Skeletal; Sympathetic Nervous System; Pressoreceptors; Lower Extremity; Blood Pressure; Baroreflex; Heart Rate
PubMed: 38500058
DOI: 10.1186/s12576-024-00909-4