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Cardiovascular Toxicology Jan 2015The body responds to environmental stressors by triggering autonomic reflexes in the pulmonary receptors, baroreceptors, and chemoreceptors to maintain homeostasis.... (Review)
Review
The body responds to environmental stressors by triggering autonomic reflexes in the pulmonary receptors, baroreceptors, and chemoreceptors to maintain homeostasis. Numerous studies have shown that exposure to various gases and airborne particles can alter the functional outcome of these reflexes, particularly with respect to the cardiovascular system. Modulation of autonomic neural input to the heart and vasculature following direct activation of sensory nerves in the respiratory system, elicitation of oxidative stress and inflammation, or through other mechanisms is one of the primary ways that exposure to air pollution affects normal cardiovascular function. Any homeostatic process that utilizes the autonomic nervous system to regulate organ function might be affected. Thus, air pollution and other inhaled environmental irritants have the potential to alter both local airway function and baro- and chemoreflex responses, which modulate autonomic control of blood pressure and detect concentrations of key gases in the body. While each of these reflex pathways causes distinct responses, the systems are heavily integrated and communicate through overlapping regions of the brainstem to cause global effects. This short review summarizes the function of major pulmonary sensory receptors, baroreceptors, and carotid body chemoreceptors and discusses the impacts of air pollution exposure on these systems.
Topics: Air Pollution; Autonomic Nervous System; Cardiovascular System; Chemoreceptor Cells; Heart Rate; Humans; Lung; Pressoreceptors; Respiratory Physiological Phenomena; Sensory Receptor Cells
PubMed: 25123706
DOI: 10.1007/s12012-014-9272-0 -
Autonomic Neuroscience : Basic &... Sep 2022A reciprocal relationship between the baroreflex and cerebral autoregulation (CA) has been demonstrated at rest and in response to acute hypotension. We hypothesized... (Review)
Review
A reciprocal relationship between the baroreflex and cerebral autoregulation (CA) has been demonstrated at rest and in response to acute hypotension. We hypothesized that the reciprocal relationship between cardiac baroreflex sensitivity (BRS) and CA would be maintained during sustained central hypovolemia induced by lower body negative pressure (LBNP), and that the strength of this relationship would be greater in subjects with higher tolerance to this stress. Healthy young adults (n = 51; 23F/28M) completed a LBNP protocol to presyncope. Subjects were classified as high tolerant (HT; completion of -60 mmHg LBNP stage, ≥20-min) or low tolerant (LT; did not complete -60 mmHg LBNP stage, <20-min). R-R intervals (RRI), systolic arterial pressure (SAP), mean arterial pressure (MAP), and middle cerebral artery velocity (MCAv) were measured continuously. Cardiac BRS was calculated in the time domain (ΔHR/ΔSAP) and frequency domain (RRI-SAP low frequency (LF) transfer function gain), and CA was calculated in the time domain (ΔMCAv/ΔMAP) and frequency domain (MAP-mean MCAv LF transfer function gain). There was a moderate relationship between cardiac BRS and CA for the group of 51 subjects in both the time (R = -0.54, P < 0.0001) and frequency (R = 0.61, P < 0.001) domains; there was a stronger relationship in the HT group (R = 0.73) compared to the LT group (R = 0.31) in the frequency domain (P = 0.08), but no difference between groups in the time domain (HT: R = -0.73 vs. LT: R = -0.63; P = 0.27). These findings suggest that an interaction between BRS and CA may be an important compensatory mechanism that contributes to tolerance to simulated hemorrhage in young healthy adults.
Topics: Blood Pressure; Heart Rate; Hemorrhage; Homeostasis; Humans; Lower Body Negative Pressure; Pressoreceptors; Young Adult
PubMed: 35716525
DOI: 10.1016/j.autneu.2022.103007 -
Circulation Research Jul 2021
Topics: Blood Pressure; Kidney; Pressoreceptors; Renin
PubMed: 34236885
DOI: 10.1161/CIRCRESAHA.121.319559 -
Physiology (Bethesda, Md.) Mar 2015Because of resetting, a role for baroreflexes in long-term control of arterial pressure has been commonly dismissed in the past. However, in recent years, this... (Review)
Review
Because of resetting, a role for baroreflexes in long-term control of arterial pressure has been commonly dismissed in the past. However, in recent years, this perspective has changed. Novel approaches for determining chronic neurohormonal and cardiovascular responses to natural variations in baroreceptor activity and to electrical stimulation of the carotid baroreflex indicate incomplete resetting and sustained responses that lead to long-term alterations in sympathetic activity and arterial pressure.
Topics: Animals; Antihypertensive Agents; Arterial Pressure; Baroreflex; Cardiovascular System; Homeostasis; Humans; Hypertension; Mechanotransduction, Cellular; Models, Cardiovascular; Obesity; Pressoreceptors; Renin-Angiotensin System; Time Factors
PubMed: 25729060
DOI: 10.1152/physiol.00035.2014 -
Kidney360 Dec 2022Heart failure is the most common cardiovascular complication of chronic kidney disease (CKD) and foreshadows a high morbidity and mortality rate. Baroreflex impairment...
BACKGROUND
Heart failure is the most common cardiovascular complication of chronic kidney disease (CKD) and foreshadows a high morbidity and mortality rate. Baroreflex impairment likely contributes to cardiovascular mortality. We aimed to study the associations between CKD, heart failure, and baroreflex sensitivity (BRS) and their association with cardiovascular outcomes.
METHODS
We retrospectively analyzed data from a cohort of 247 individuals with moderate to severe HF. All subjects underwent BRS measurements after intravenous phenylephrine along with electrocardiography, echocardiography, and laboratory measurements. We used logistic regression models to assess the association of CKD (estimated glomerular filtration rate <60 ml/min per 1.73 m) with BRS using iterative models. Cox proportional hazards models were used to assess associations of binary BRS and subgroups according to categorizations of CKD and BRS with cardiovascular mortality.
RESULTS
Median eGFR among individuals with CKD was 52 (IQR 44-56) ml/min per 1.73 m. eGFR was lower in those with depressed BRS (65 [IQR 54-76] ml/min per 1.73 m) compared with those with preserved BRS (73 [IQR 64-87] ml/min per 1.73 m; ≤0.001). The majority of individuals with CKD had depressed BRS compared with those without CKD (60% versus 29%; =0.05). In regression models, CKD and BRS were independently associated. Cardiovascular mortality was significantly increased in individuals with or without CKD and depressed BRS compared with those with preserved BRS and CKD.
CONCLUSIONS
Cardiac BRS is depressed in patients with mild to moderate CKD and HF and associated with cardiovascular mortality. Additional study to confirm its contribution to cardiovascular mortality, particularly in advanced CKD, is warranted.
Topics: Humans; Pressoreceptors; Retrospective Studies; Heart Failure; Kidney; Renal Insufficiency, Chronic
PubMed: 36591344
DOI: 10.34067/KID.0004812022 -
Neurological Sciences : Official... Jan 2021Initial cardiovascular fingolimod effects might compromise baroreflex responses to rapid blood pressure (BP) changes during common Valsalva-like maneuvers. This study...
BACKGROUND AND PURPOSE
Initial cardiovascular fingolimod effects might compromise baroreflex responses to rapid blood pressure (BP) changes during common Valsalva-like maneuvers. This study evaluated cardiovascular responses to Valsalva maneuver (VM)-induced baroreceptor unloading and loading upon fingolimod initiation.
PATIENTS AND METHODS
Twenty-one patients with relapsing-remitting multiple sclerosis performed VMs before and 0.5, 1, 2, 3, 4, 5, and 6 hours after fingolimod initiation. We recorded heart rate (HR) as RR intervals (RRI), systolic and diastolic BP (BPsys, BPdia) during VM phase 1, VM phase 2 early, VM phase 2 late, and VM phase 4. Using linear regression analysis between decreasing BPsys and RRI values during VM phase 2 early, we determined baroreflex gain (BRG) reflecting vagal withdrawal and sympathetic activation upon baroreceptor unloading. To assess cardiovagal activation upon baroreceptor loading, we calculated Valsalva ratios (VR) between maximal and minimal RRIs after strain release. Analysis of variance or Friedman tests with post hoc analysis compared corresponding parameters at the eight time points (significance: p < 0.05).
RESULTS
RRIs at VM phase 1, VM phase 2 early, and VM phase 2 late were higher after than before fingolimod initiation, and maximal after 4 hours. Fingolimod did not affect the longest RRIs upon strain release, but after 3, 5, and 6 hours lowered the highest BPsys values during overshoot and all BPdia values, and thus reduced VRs. BRG was slightly higher after 3 and 5 hours, and significantly higher after 4 hours than before fingolimod initiation.
CONCLUSIONS
VR-decreases 3-6 hours after fingolimod initiation are physiologic results of fingolimod-associated attenuations of BP and HR increases at the end of strain and do not suggest impaired cardiovagal activation upon baroreceptor loading. Stable and at the time of HR nadir significantly increased BRGs indicate improved responses to baroreceptor unloading. Thus, cardiovascular fingolimod effects do not impair autonomic responses to sudden baroreceptor loading or unloading but seem to be mitigated by baroreflex resetting.
Topics: Baroreflex; Blood Pressure; Fingolimod Hydrochloride; Heart Rate; Humans; Pressoreceptors; Valsalva Maneuver
PubMed: 33443674
DOI: 10.1007/s10072-020-05004-1 -
Journal of the American Society of... Jun 2019
Review
Topics: Animals; Humans; Ion Channels; Mechanotransduction, Cellular; Mice; Pressoreceptors; Sensitivity and Specificity
PubMed: 31043433
DOI: 10.1681/ASN.2019020160 -
Cell Reports Nov 2019Soohong et al. (2019) reveal a class of vagal afferents-defined by Piezo2 expression-that innervate the aorta and function to sense blood pressure fluctuations. Their...
Soohong et al. (2019) reveal a class of vagal afferents-defined by Piezo2 expression-that innervate the aorta and function to sense blood pressure fluctuations. Their study describes the morphologies and role of these neurons in vascular regulation.
Topics: Animals; Aorta; Baroreflex; Blood Pressure; Hoof and Claw; Pressoreceptors
PubMed: 31747586
DOI: 10.1016/j.celrep.2019.11.031 -
Circulation. Arrhythmia and... Apr 2021Symptomatic heart failure (HF) patients despite optimal medical therapy and advances such as invasive hemodynamic monitoring remain challenging to manage. While cardiac... (Review)
Review
Symptomatic heart failure (HF) patients despite optimal medical therapy and advances such as invasive hemodynamic monitoring remain challenging to manage. While cardiac resynchronization therapy remains a highly effective therapy for a subset of HF patients with wide QRS, a majority of symptomatic HF patients are poor candidates for such. Recently, cardiac contractility modulation, neuromodulation based on carotid baroreceptor stimulation, and phrenic nerve stimulation have been approved by the US Food and Drug Administration and are emerging as therapeutic options for symptomatic HF patients. This state-of-the-art review examines the role of these evolving electrical therapies in advanced HF.
Topics: Animals; Autonomic Nervous System; Cardiac Pacing, Artificial; Electric Stimulation Therapy; Heart; Heart Failure; Humans; Myocardial Contraction; Pacemaker, Artificial; Prevalence; Recovery of Function; Spinal Cord Stimulation; Stroke Volume; Treatment Outcome; Vagus Nerve Stimulation; Ventricular Function, Left
PubMed: 33858178
DOI: 10.1161/CIRCEP.120.009668 -
Experimental Physiology Jun 2018What is the central question of this study? Whether anaphylaxis affects sympathetic outflows to the brown adipose tissue (BAT) and adrenal gland and whether anaphylaxis...
NEW FINDINGS
What is the central question of this study? Whether anaphylaxis affects sympathetic outflows to the brown adipose tissue (BAT) and adrenal gland and whether anaphylaxis affects some brain areas in association with sympathetic regulation. What is the main finding and its importance? Sympathoexcitatory responses to anaphylaxis occurred regionally in the kidney and adrenal gland, but not in the thermogenesis-related BAT. Further, anaphylactic hypotension also caused increase in c-fos immunoreactivity in the hypothalamic and medullary areas. Moreover, catecholaminergic neurons of the brainstem cause adrenal sympathoexcitation in a baroreceptor-independent manner.
ABSTRACT
We previously reported that sympathetic nerve activity (SNA) to the kidney and the hindlimb increases during anaphylactic hypotension in anaesthetized rats. Based on this evidence, we examined effects of anaphylactic hypotension on SNA to the brown adipose tissue (BAT), and the adrenal gland and kidney in anaesthetized rats. We demonstrated that adrenal and renal SNA, but not BAT-SNA, were stimulated. In addition, the effects of anaphylaxis on neural activities of the hypothalamic and medullary nuclei, which are candidates for relaying efferent SNA to the peripheral organs, were investigated via immunohistochemical staining of c-fos. Anaphylaxis increased c-fos expression in the neurons of the paraventricular nucleus (PVN) of the hypothalamus and in those of the nucleus tractus solitarii (NTS) and rostral ventrolateral medulla (RVLM) of the medulla oblongata; c-fos was expressed in γ-aminobutyric acid (GABA)-ergic neurons of the NTS and in the catecholaminergic neurons of the RVLM. In addition, c-fos expression in the rostral NTS and mid NTS during anaphylaxis was reduced by sinoaortic baroreceptor denervation; however, increased c-fos expression in the caudal NTS and RVLM or adrenal sympathoexcitation were not affected by sinoaortic baroreceptor denervation. These results indicated that anaphylactic hypotension activates the hypothalamic PVN and the medullary NTS and RVLM independently of the baroreflex pathway. Further, it stimulated efferent SNA to the adrenal gland and kidney to restore blood pressure.
Topics: Adipose Tissue, Brown; Anaphylaxis; Animals; Baroreflex; Blood Pressure; Denervation; Hypotension; Kidney; Male; Neurons; Paraventricular Hypothalamic Nucleus; Pressoreceptors; Proto-Oncogene Proteins c-fos; Rats; Rats, Sprague-Dawley; Solitary Nucleus; Sympathetic Nervous System; Thermogenesis
PubMed: 29524326
DOI: 10.1113/EP086809