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Circulation Research Aug 2016
Topics: Baroreflex; Blood Pressure; Heart Rate; Pressoreceptors
PubMed: 27539969
DOI: 10.1161/CIRCRESAHA.116.309392 -
Comprehensive Physiology Feb 2021Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain cardiovascular homeostasis by coordinating the responses to external and...
Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain cardiovascular homeostasis by coordinating the responses to external and internal environmental stressors. While it is well known that carotid and cardiopulmonary baroreceptors modulate sympathetic vasomotor and parasympathetic cardiac neural autonomic drive, to avoid excessive fluctuations in vascular tone and maintain intravascular volume, there is increasing recognition that baroreceptors also modulate a wide range of non-cardiovascular physiological responses via projections from the nucleus of the solitary tract to regions of the central nervous system, including the spinal cord. These projections regulate pain perception, sleep, consciousness, and cognition. In this article, we summarize the physiology of baroreceptor pathways and responses to baroreceptor activation with an emphasis on the mechanisms influencing cardiovascular function, pain perception, consciousness, and cognition. Understanding baroreceptor-mediated effects on cardiac and extra-cardiac autonomic activities will further our understanding of the pathophysiology of multiple common clinical conditions, such as chronic pain, disorders of consciousness (e.g., abnormalities in sleep-wake), and cognitive impairment, which may result in the identification and implementation of novel treatment modalities. © 2021 American Physiological Society. Compr Physiol 11:1373-1423, 2021.
Topics: Consciousness; Heart; Humans; Pain; Parasympathetic Nervous System; Pressoreceptors; Sympathetic Nervous System
PubMed: 33577130
DOI: 10.1002/cphy.c190038 -
Scientific Reports Jul 2022Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits, but neuromodulation of aortic baroreceptor afferents remains unexplored for...
Carotid baroreceptor stimulation has been clinically explored for antihypertensive benefits, but neuromodulation of aortic baroreceptor afferents remains unexplored for potential translation into the clinic. Published studies have used supramaximal stimulations, which are unphysiological and energy inefficient. The objective of the present study was to identify optimal low-charge nerve stimulation parameters that would provide a clinically-relevant (20-30 mmHg) decrease in mean arterial pressure (MAP) in anesthetized spontaneously hypertensive rats. Stimulations of 20 s were delivered to the left aortic depressor nerve (ADN) of these rats using low ranges of pulse amplitudes (≤ 0.6 mA), widths (≤ 0.5 ms) and frequencies (≤ 5 Hz). We also assessed the effects of continuous (20 s) versus intermittent (5 s ON/3 s OFF and 5 s ON/3 s OFF for 20 s) stimulation on MAP, heart rate (HR), mesenteric (MVR) and femoral (FVR) vascular resistance using low (5 Hz) and high (15 Hz) frequencies. Lower pulse amplitudes (0.2 mA) produced 9 ± 2 to 18 ± 2 mmHg decreases in MAP. Higher pulse amplitudes (0.4 mA) produced a median MAP reduction of 28 ± 4 mmHg at 0.2 ms and 5 Hz, with no added benefit seen above 0.4 mA. Continuous and intermittent low frequency stimulation at 0.4 mA and 0.2 ms produced similar sustained decreases in MAP, HR, MVR and FVR. Continuous high frequency stimulation at 0.4 mA and 0.2 ms produced larger reductions in MAP, HR, MVR and FVR compared with all low frequency and/or intermittent high frequency stimulations. We conclude from these findings that "low intensity intermittent" electrical stimulation is an effective alternate way for neuromodulation of the aortic baroreceptor afferents and to evoke a required restoration of MAP levels in spontaneously hypertensive rats. This approach enables low energy consumption and markedly lowers the excessive decreases in MAP and hemodynamic disturbances elicited by continuous high-charge injection protocols.
Topics: Animals; Aorta; Blood Pressure; Electric Stimulation; Heart Rate; Hypertension; Pressoreceptors; Rats; Rats, Inbred SHR
PubMed: 35851099
DOI: 10.1038/s41598-022-15761-y -
Experimental Physiology Sep 2019What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and...
NEW FINDINGS
What is the central question of this study? The traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation, which does not permit their individual study in different situations. What is the main finding and its importance? We have described a new surgical approach capable of selective denervation of the arterial (aortic and carotid) baroreceptors, keeping the carotid bodies (chemoreceptors) intact. It is understood that this technique might be a useful tool for investigating the relative role of the baro- and chemoreceptors in several physiological and pathophysiological conditions.
ABSTRACT
Studies have demonstrated that the traditional surgical approach for sino-aortic denervation in rats leads to simultaneous carotid baroreceptor and chemoreceptor deactivation. The present study reports a new surgical approach to denervate the aortic and the carotid baroreceptors selectively, keeping the carotid bodies (peripheral chemoreceptors) intact. Wistar rats were subjected to specific aortic and carotid baroreceptor denervation (BAROS-X) or sham surgery (SHAM). Baroreflex activation was achieved by i.v. administration of phenylephrine, whereas peripheral chemoreflex activation was produced by i.v. administration of potassium cyanide. The SHAM and BAROS-X rats displayed significant hypertensive responses to phenylephrine administration. However, the reflex bradycardia following the hypertensive response caused by phenylephrine was remarkable in SHAM, but not significant in the BAROS-X animals, confirming the efficacy of the surgical procedure to abolish the baroreflex. In addition, the baroreflex activation elicited by phenylephrine increased carotid sinus nerve activity only in SHAM, but not in the BAROS-X animals, providing support to the notion that the baroreceptor afferents were absent. Instead, the classical peripheral chemoreflex hypertensive and bradycardic responses to potassium cyanide were similar in both groups, suggesting that the carotid body chemoreceptors were preserved after BAROS-X. In summary, we describe a new surgical approach in which only the baroreceptors are eliminated, while the carotid chemoreceptors are preserved. Therefore, it is understood that this procedure is potentially a useful tool for examining the relative roles of the arterial baroreceptors versus the chemoreceptors in several pathophysiological conditions, for instance, arterial hypertension and heart failure.
Topics: Animals; Aorta; Arteries; Baroreflex; Blood Pressure; Carotid Body; Chemoreceptor Cells; Denervation; Heart Rate; Hypertension; Male; Phenylephrine; Pressoreceptors; Rats; Rats, Wistar
PubMed: 31161612
DOI: 10.1113/EP087764 -
Neuroscience Bulletin Oct 2021Mechanosensitive ion channels (MSCs) are key molecules in the mechano-electrical transduction of arterial baroreceptors. Among them, acid-sensing ion channel 2 (ASIC2)...
Mechanosensitive ion channels (MSCs) are key molecules in the mechano-electrical transduction of arterial baroreceptors. Among them, acid-sensing ion channel 2 (ASIC2) and transient receptor potential vanilloid subfamily member 1 (TRPV1) have been studied extensively and documented to play important roles. In this study, experiments using aortic arch-aortic nerve preparations isolated from rats revealed that both ASIC2 and TRPV1 are functionally necessary, as blocking either abrogated nearly all pressure-dependent neural discharge. However, whether ASIC2 and TRPV1 work in coordination remained unclear. So we carried out cell-attached patch-clamp recordings in HEK293T cells co-expressing ASIC2 and TRPV1 and found that inhibition of ASIC2 completely blocked stretch-activated currents while inhibition of TRPV1 only partially blocked these currents. Immunofluorescence staining of aortic arch-aortic adventitia from rats showed that ASIC2 and TRPV1 are co-localized in the aortic nerve endings, and co-immunoprecipitation assays confirmed that the two proteins form a compact complex in HEK293T cells and in baroreceptors. Moreover, protein modeling analysis, exogenous co-immunoprecipitation assays, and biotin pull-down assays indicated that ASIC2 and TRPV1 interact directly. In summary, our research suggests that ASIC2 and TRPV1 form a compact complex and function synergistically in the mechano-electrical transduction of arterial baroreceptors. The model of synergism between MSCs may have important biological significance beyond ASIC2 and TRPV1.
Topics: Acid Sensing Ion Channels; Animals; HEK293 Cells; Humans; Pressoreceptors; Rats; TRPV Cation Channels
PubMed: 34215968
DOI: 10.1007/s12264-021-00737-1 -
American Journal of Physiology. Heart... Nov 2018Two powerful reflexes controlling cardiovascular function during exercise are the muscle metaboreflex and arterial baroreflex. In heart failure (HF), the strength and...
Two powerful reflexes controlling cardiovascular function during exercise are the muscle metaboreflex and arterial baroreflex. In heart failure (HF), the strength and mechanisms of these reflexes are altered. Muscle metaboreflex activation (MMA) in normal subjects increases mean arterial pressure (MAP) primarily via increases in cardiac output (CO), whereas in HF the mechanism shifts to peripheral vasoconstriction. Baroreceptor unloading increases MAP via peripheral vasoconstriction, and this pressor response is blunted in HF. Baroreceptor unloading during MMA in normal animals elicits an enormous pressor response via combined increases in CO and peripheral vasoconstriction. The mode of interaction between these reflexes is intimately dependent on the parameter (e.g., MAP and CO) being investigated. The interaction between the two reflexes when activated simultaneously during dynamic exercise in HF is unknown. We activated the muscle metaboreflex in chronically instrumented dogs during mild exercise (via graded reductions in hindlimb blood flow) followed by baroreceptor unloading [via bilateral carotid occlusion (BCO)] before and after induction of HF. We hypothesized that BCO during MMA in HF would cause a smaller increase in MAP and a larger vasoconstriction of ischemic hindlimb vasculature, which would attenuate the restoration of blood flow to ischemic muscle observed in normal dogs. We observed that BCO during MMA in HF increases MAP by substantial vasoconstriction of all vascular beds, including ischemic active muscle, and that all cardiovascular responses, except ventricular function, exhibit occlusive interaction. We conclude that vasoconstriction of ischemic active skeletal muscle in response to baroreceptor unloading during MMA attenuates restoration of hindlimb blood flow. NEW & NOTEWORTHY We found that baroreceptor unloading during the muscle metaboreflex in heart failure results in occlusive interaction (except for ventricular function) with significant vasoconstriction of all vascular beds. In addition, restoration of blood flow to ischemic active muscle, via preferentially larger vasoconstriction of nonischemic beds, is significantly attenuated in heart failure.
Topics: Adaptation, Physiological; Animals; Arterial Pressure; Baroreflex; Cardiac Output; Chemoreceptor Cells; Disease Models, Animal; Dogs; Energy Metabolism; Female; Heart Failure; Hindlimb; Male; Muscle Contraction; Muscle, Skeletal; Pressoreceptors; Regional Blood Flow; Time Factors; Vasoconstriction
PubMed: 30074841
DOI: 10.1152/ajpheart.00338.2018 -
BMJ Case Reports Oct 2017Orthostatic hypotension has a vast differential that has been previously described throughout the literature. However, baroreceptor failure as a sequela of head and neck...
Orthostatic hypotension has a vast differential that has been previously described throughout the literature. However, baroreceptor failure as a sequela of head and neck radiation is not often recognised as an important cause of dramatic haemodynamic variability. As a result, individuals suffering from baroreceptor failure likely have been undertreated. Herein, we report a case of a patient with a history of radiation to the neck for squamous cell carcinoma of the tongue and resultant baroreceptor failure resulting in syncope.
Topics: Aged; Carcinoma, Squamous Cell; Humans; Hypotension, Orthostatic; Male; Pressoreceptors; Radiotherapy, Intensity-Modulated; Syncope; Tongue Neoplasms; Treatment Outcome
PubMed: 29025783
DOI: 10.1136/bcr-2017-221925 -
Scientific Reports Nov 2021Arterial baroreceptors (BRs) play a vital role in the regulation of the cardiopulmonary system. What is known about how these sensors operate at the subcellular level is...
Arterial baroreceptors (BRs) play a vital role in the regulation of the cardiopulmonary system. What is known about how these sensors operate at the subcellular level is limited, however. Until recently, one afferent axon was considered to be connected to a single baroreceptor (one-sensor theory). However, in the lung, a single airway mechanosensory unit is now known to house many sensors (multiple-sensor theory). Here we tested the hypothesis that multiple-sensor theory also operates in BR units, using both morphological and electrophysiological approaches in rabbit aortic arch (in whole mount) labeled with Na/K-ATPase, as well as myelin basic protein antibodies, and examined microscopically. Sensory structures presented in compact clusters, similar to bunches of grapes. Sensory terminals, like those in the airways, formed leaf-like or knob-like expansions. That is, a single myelinated axon connected with multiple sensors forming a network. We also recorded single-unit activities from aortic baroreceptors in the depressor nerve in anesthetized rabbits and examined the unit response to a bolus intravenous injection of phenylephrine. Unit activity increased progressively as blood pressure (BP) increased. Five of eleven units abruptly changed their discharge pattern to a lower activity level after BP attained a plateau for a minute or two (when BP was maintained at the high level). These findings clearly show that the high discharge baroreceptor deactivates after over-excitation and unit activity falls to a low discharge sensor. In conclusion, our morphological and physiological data support the hypothesis that multiple-sensory theory can be applied to BR units.
Topics: Animals; Antibodies; Aorta; Aorta, Thoracic; Axons; Blood Pressure; Electrophysiology; Lung; Male; Models, Neurological; Myelin Basic Protein; Phenylephrine; Pressoreceptors; Rabbits; Sodium-Potassium-Exchanging ATPase
PubMed: 34848803
DOI: 10.1038/s41598-021-02563-x -
Journal of Lipid Research Jul 2019The sympathetic nervous system (SNS) regulates the functions of white adipose tissue (WAT) and brown adipose tissue (BAT) tightly. Carotid baroreceptor stimulation (CBS)...
The sympathetic nervous system (SNS) regulates the functions of white adipose tissue (WAT) and brown adipose tissue (BAT) tightly. Carotid baroreceptor stimulation (CBS) efficiently inhibits SNS activation. We hypothesized that CBS would protect against obesity. We administered CBS to obese rats and measured sympathetic and AMP-activated protein kinase (AMPK)/ PPAR pathway responses as well as changes in perirenal WAT (PWAT), epididymal WAT (EWAT), and interscapular BAT (IBAT). CBS alleviated obesity-related metabolic changes, improving insulin resistance; reducing adipocyte hypertrophy, body weight, and adipose tissue weights; and decreasing norepinephrine but increasing acetylcholine in plasma, PWAT, EWAT, and IBAT. CBS also downregulated fatty acid translocase (CD36), fatty acid transport protein (FATP), phosphorylated and total hormone sensitive lipase, phosphorylated and total protein kinase A, and PPARγ in obese rats. Simultaneously, CBS upregulated phosphorylated adipose triglyceride lipase, phosphorylated and total AMPK, and PPARα in PWAT, EWAT, and IBAT. However, BAT and WAT responses differed; although many responses were more sensitive in IBAT, responses of CD36, FATP, and PPARγ were more sensitive in PWAT and EWAT. Overall, CBS decreased chronically activated SNS and ameliorated obesity-related metabolic disorders by regulating the AMPK/PPARα/γ pathway.
Topics: Adipose Tissue, Brown; Adipose Tissue, White; Animals; Carotid Sinus; Electric Stimulation Therapy; Glucose Tolerance Test; Male; Obesity; Pressoreceptors; Rats; Rats, Sprague-Dawley; Sympathetic Nervous System
PubMed: 31126973
DOI: 10.1194/jlr.M091256 -
PloS One 2018To explore noninvasively the complex interactions of the maternal hemodynamic system throughout pregnancy and the resulting after-effect six weeks postpartum.
OBJECTIVE
To explore noninvasively the complex interactions of the maternal hemodynamic system throughout pregnancy and the resulting after-effect six weeks postpartum.
METHODS
Eighteen women were tested beginning at the 12th week of gestation at six time-points throughout pregnancy and six weeks postpartum. Heart rate, heart rate variability, blood pressure, pulse transit time (PTT), respiration, and baroreceptor sensitivity were analyzed in resting conditions. Additionally, hemoglobin, asymmetric and symmetric dimethylarginine and Endothelin (ET-1) were obtained.
RESULTS
Heart rate and sympathovagal balance favoring sympathetic drive increased, the vagal tone and the baroreflex sensitivity decreased during pregnancy. Relative sympathetic drive (sympathovagal balance) reached a maximum at 6 weeks postpartum whereas the other variables did not differ compared to first trimester levels. Postpartum diastolic blood pressure was higher compared to first and second trimester. Pulse transit time and endothelial markers showed no difference throughout gestation. However, opposing variables PTT and asymmetric dimethylarginine (ADMA) were both higher six weeks postpartum.
CONCLUSIONS
The sympathetic up regulation throughout pregnancy goes hand in hand with a decreased baroreflex sensitivity. In the postpartum period, the autonomic nervous system, biochemical endothelial reactions and PTT show significant and opposing changes compared to pregnancy findings, indicating the complex aftermath of the increase of blood volume, the changes in perfusion strategies and blood pressure regulation that occur in pregnancy.
Topics: Adult; Arginine; Baroreflex; Blood Pressure; Cardiovascular Physiological Phenomena; Endothelin-1; Endothelium; Female; Heart Rate; Hemodynamics; Hemoglobins; Humans; Postpartum Period; Pregnancy; Pregnancy Trimesters; Pressoreceptors; Prospective Studies
PubMed: 29782509
DOI: 10.1371/journal.pone.0197748