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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 -
EuroIntervention : Journal of EuroPCR... May 2013The contribution of sympathetic activation in the development of hypertension is supported by early experimental evidence based on surgical denervation of sino-aortic... (Review)
Review
The contribution of sympathetic activation in the development of hypertension is supported by early experimental evidence based on surgical denervation of sino-aortic baroreceptors or lesions of the central relay station of the baroreflex, the nucleus tractus solitarii. Disruption of this area of the brain was associated with an immediate increase in blood pressure. Sympathetic overactivity can also be triggered by impairment of the inhibitory function physiologically exerted by reflexogenic areas (arterial baroreceptors, cardiopulmonary receptors, and chemoreceptors) on adrenergic drive. Metabolic and humoral mechanisms are also thought to be involved in the development and progression of hypertension-related sympathetic overdrive.
Topics: Animals; Antihypertensive Agents; Baroreflex; Blood Pressure; Drug Resistance; Electric Stimulation Therapy; Humans; Hypertension; Pressoreceptors; Treatment Outcome
PubMed: 23732146
DOI: 10.4244/EIJV9SRA23 -
Hypertension (Dallas, Tex. : 1979) May 2011Recent technical advances have renewed interest in device-based therapy for the treatment of drug-resistant hypertension. Findings from recent clinical trials regarding... (Review)
Review
Recent technical advances have renewed interest in device-based therapy for the treatment of drug-resistant hypertension. Findings from recent clinical trials regarding the efficacy of electric stimulation of the carotid sinus for the treatment of resistant hypertension are reviewed here. The main goal of this article, however, is to summarize the preclinical studies that have provided insight into the mechanisms that account for the chronic blood pressure-lowering effects of carotid baroreflex activation. Some of the mechanisms identified were predictable and confirmed by experimentation. Others have been surprising and controversial, and resolution will require further investigation. Although feasibility studies have been promising, firm conclusions regarding the value of this device-based therapy for the treatment of resistant hypertension awaits the results of current multicenter trials.
Topics: Baroreflex; Blood Pressure; Carotid Sinus; Humans; Hypertension; Kidney; Pressoreceptors
PubMed: 21357283
DOI: 10.1161/HYPERTENSIONAHA.108.119859 -
Autonomic Neuroscience : Basic &... Apr 2013Second order neurons in the nucleus tractus solitarius (NTS) process and integrate the afferent information from arterial baroreceptors with high fidelity and precise... (Review)
Review
Second order neurons in the nucleus tractus solitarius (NTS) process and integrate the afferent information from arterial baroreceptors with high fidelity and precise timing synaptic transmission. Since 2nd-order NTS neurons receiving baroreceptors inputs are relatively well characterized, their electrophysiological profile has been accepted as a general characteristic for all 2nd-order NTS neurons involved with the processing of different sensorial inputs. On the other hand, the synaptic properties of other afferent systems in NTS, such as the peripheral chemoreceptors, are not yet well understood. In this context, in previous studies we demonstrated that in response to repetitive afferents stimulation, the chemoreceptors 2nd-order NTS neurons also presented high fidelity of synaptic transmission, but with a large variability in the latency of evoked responses. This finding is different in relation to the precise timing transmission for baroreceptor 2nd-order NTS neurons, which was accepted as a general characteristic profile for all 2nd order neurons in the NTS. In this brief review we discuss this new concept as an index of complexity of the sensorial inputs to NTS with focus on the synaptic processing of baro- and chemoreceptor afferents.
Topics: Animals; Chemoreceptor Cells; Excitatory Postsynaptic Potentials; Humans; Neurons; Pressoreceptors; Solitary Nucleus; Synaptic Transmission
PubMed: 23305891
DOI: 10.1016/j.autneu.2012.12.002 -
Digestion 2020Transient receptor potential vanilloid 4 (TRPV4) is activated by stretch (mechanical), warm temperature, some epoxyeicosatrienoic acids, and lipopolysaccharide. TRPV4 is... (Review)
Review
Transient Receptor Potential Vanilloid 4 Regulation of Adenosine Triphosphate Release by the Adenosine Triphosphate Transporter Vesicular Nucleotide Transporter, a Novel Therapeutic Target for Gastrointestinal Baroreception and Chronic Inflammation.
BACKGROUND
Transient receptor potential vanilloid 4 (TRPV4) is activated by stretch (mechanical), warm temperature, some epoxyeicosatrienoic acids, and lipopolysaccharide. TRPV4 is expressed throughout the gastrointestinal epithelia and its activation induces adenosine triphosphate (ATP) exocytosis that is involved in visceral hypersensitivity. As an ATP transporter, vesicular nucleotide transporter (VNUT) mediates ATP storage in secretory vesicles and ATP release via exocytosis upon stimulation.
SUMMARY
TRPV4 is sensitized under inflammatory conditions by a variety of factors, including proteases and serotonin, whereas methylation-dependent silencing of TRPV4 expression is associated with various pathophysiological conditions. Gastrointestinal epithelia also release ATP in response to hypo-osmolality or acid through molecular mechanisms that remain unclear. These synergistically released ATP could be involved in visceral hypersensitivity. Low concentrations of the first generation bisphosphate, clodronate, were recently reported to inhibit VNUT activity and thus clodronate may be a safe and potent therapeutic option to treat visceral pain. Key Messages: This review focuses on: (1) ATP and TRPV4 activities in gastrointestinal epithelia; (2) factors that could modulate TRPV4 activity in gastrointestinal epithelia; and (3) the inhibition of VNUT as a potential novel therapeutic strategy for functional gastrointestinal disorders.
Topics: Abdominal Pain; Adenosine Triphosphate; Analgesics; Animals; Chronic Disease; Clodronic Acid; Gastrointestinal Tract; Humans; Inflammation; Mice; Mucous Membrane; Nucleotide Transport Proteins; Pressoreceptors; Receptors, Purinergic P2; TRPV Cation Channels
PubMed: 31770754
DOI: 10.1159/000504021 -
Journal of Neurophysiology Sep 2019Baroreceptors play a pivotal role in the regulation of blood pressure through moment to moment sensing of arterial blood pressure and providing information to the...
Baroreceptors play a pivotal role in the regulation of blood pressure through moment to moment sensing of arterial blood pressure and providing information to the central nervous system to make autonomic adjustments to maintain appropriate tissue perfusion. A recent publication by Zeng and colleagues (Zeng WZ, Marshall KL, Min S, Daou I, Chapleau MW, Abboud FM, Liberles SD, 362: 464-467, 2018) suggests the mechanosensitive ion channels Piezo1 and Piezo2 represent the cellular mechanism by which baroreceptor nerve endings sense changes in arterial blood pressure. However, before Piezo1 and Piezo2 are accepted as the sensor of baroreceptors, the question must be asked of what criteria are necessary to establish this and how well the report of Zeng and colleagues (Zeng WZ, Marshall KL, Min S, Daou I, Chapleau MW, Abboud FM, Liberles SD, 362: 464-467, 2018) satisfies these criteria. We briefly review baroreceptor function, outline criteria that a putative neuronal sensor of blood pressure must satisfy, and discuss whether the recent findings of Zeng and colleagues suitably meet these criteria. Despite the provocative hypothesis, there are significant concerns regarding the evidence supporting a role of Piezo1/Piezo2 in arterial baroreceptor function.
Topics: Animals; Autonomic Nervous System; Baroreflex; Blood Pressure; Humans; Ion Channels; Pressoreceptors
PubMed: 31314636
DOI: 10.1152/jn.00315.2019 -
Experimental Physiology May 2021Cardio-ventilatory coupling refers to the onset of inspiration occurring at a preferential latency following the last heartbeat (HB) in expiration. According to the...
NEW FINDINGS
Cardio-ventilatory coupling refers to the onset of inspiration occurring at a preferential latency following the last heartbeat (HB) in expiration. According to the cardiac-trigger hypothesis, the pulse pressure initiates an inspiration via baroreceptor activation. However, the central neural substrate mediating this coupling remains undefined. Using a combination of animal data, human data and mathematical modelling, this study tests the hypothesis that the HB, by way of pulsatile baroreflex activation, controls the initiation of inspiration that occurs through a rapid neural activation loop from the carotid baroreceptors to Bötzinger complex expiratory neurons.
ABSTRACT
Cardio-ventilatory coupling refers to a heartbeat (HB) occurring at a preferred latency prior to the next breath. We hypothesized that the pressure pulse generated by a HB activates baroreceptors that modulate brainstem expiratory neuronal activity and delay the initiation of inspiration. In supine male subjects, we recorded ventilation, electrocardiogram and blood pressure during 20-min epochs of baseline, slow-deep breathing and recovery. In in situ rodent preparations, we recorded brainstem activity in response to pulses of perfusion pressure. We applied a well-established respiratory network model to interpret these data. In humans, the latency between a HB and onset of inspiration was consistent across different breathing patterns. In in situ preparations, a transient pressure pulse during expiration activated a subpopulation of expiratory neurons normally active during post-inspiration, thus delaying the next inspiration. In the model, baroreceptor input to post-inspiratory neurons accounted for the effect. These studies are consistent with baroreflex activation modulating respiration through a pauci-synaptic circuit from baroreceptors to onset of inspiration.
Topics: Animals; Baroreflex; Blood Pressure; Heart Rate; Humans; Male; Pressoreceptors; Respiration
PubMed: 33749038
DOI: 10.1113/EP089365 -
Journal of Negative Results in... May 2006Aortic baroreceptors (BRs) comprise a class of cranial afferents arising from major arteries closest to the heart whose axons form the aortic depressor nerve. BRs are...
BACKGROUND
Aortic baroreceptors (BRs) comprise a class of cranial afferents arising from major arteries closest to the heart whose axons form the aortic depressor nerve. BRs are mechanoreceptors that are largely devoted to cardiovascular autonomic reflexes. Such cranial afferents have either lightly myelinated (A-type) or non-myelinated (C-type) axons and share remarkable cellular similarities to spinal primary afferent neurons. Our goal was to test whether vanilloid receptor (TRPV1) agonists, capsaicin (CAP) and resiniferatoxin (RTX), altered the pressure-discharge properties of peripheral aortic BRs.
RESULTS
Periaxonal application of 1 microM CAP decreased the amplitude of the C-wave in the compound action potential conducting at <1 m/sec along the aortic depressor nerve. 10 microM CAP eliminated the C-wave while leaving intact the A-wave conducting in the A-delta range (<12 m/sec). These whole nerve results suggest that TRPV1 receptors are expressed along the axons of C- but not A-conducting BR axons. In an aortic arch--aortic nerve preparation, intralumenal perfusion with 1 microM CAP had no effect on the pressure-discharge relations of regularly discharging, single fiber BRs (A-type)--including the pressure threshold, sensitivity, frequency at threshold, or maximum discharge frequency (n = 8, p > 0.50) but completely inhibited discharge of an irregularly discharging BR (C-type). CAP at high concentrations (10-100 microM) depressed BR sensitivity in regularly discharging BRs, an effect attributed to non-specific actions. RTX (< or = 10 microM) did not affect the discharge properties of regularly discharging BRs (n = 7, p > 0.18). A CAP-sensitive BR had significantly lower discharge regularity expressed as the coefficient of variation than the CAP-resistant fibers (p < 0.002).
CONCLUSION
We conclude that functional TRPV1 channels are present in C-type but not A-type (A-delta) myelinated aortic arch BRs. CAP has nonspecific inhibitory actions that are unlikely to be related to TRV1 binding since such effects were absent with the highly specific TRPV1 agonist RTX. Thus, CAP must be used with caution at very high concentrations.
Topics: Action Potentials; Animals; Aorta, Thoracic; Capsaicin; Diterpenes; Drug Resistance; Male; Nerve Fibers, Unmyelinated; Osmolar Concentration; Pressoreceptors; Rats; Rats, Sprague-Dawley; TRPV Cation Channels
PubMed: 16709252
DOI: 10.1186/1477-5751-5-6 -
The Yale Journal of Biology and Medicine 1986Arguments in favor of the importance of non-thermal factors in the control of skin circulation are presented. Such factors include exercise, posture, water and... (Review)
Review
Arguments in favor of the importance of non-thermal factors in the control of skin circulation are presented. Such factors include exercise, posture, water and electrolyte balance, state of training, and acclimatization. The first three factors probably elicit their effects via high- and low-pressure baroreceptors, while the mechanisms involved for the remainder are unknown.
Topics: Cardiovascular Physiological Phenomena; Humans; Ions; Neuromuscular Junction; Osmolar Concentration; Physical Exertion; Pressoreceptors; Reflex; Regional Blood Flow; Skin
PubMed: 3529655
DOI: No ID Found -
Experimental Physiology Jan 2019What is the central question of this study? After sino-aortic denervation (SAD), rats present normal levels of mean arterial pressure (MAP), high MAP variability and...
NEW FINDINGS
What is the central question of this study? After sino-aortic denervation (SAD), rats present normal levels of mean arterial pressure (MAP), high MAP variability and changes in breathing. However, mechanisms involved in SAD-induced respiratory changes and their impact on the modulation of sympathetic activity remain unclear. Herein, we characterized the firing frequency of medullary respiratory neurons after SAD. What is the main finding and its importance? Sino-aortic denervation-induced prolonged inspiration was associated with a reduced interburst frequency of pre-inspiratory/inspiratory neurons and an increased long-term variability of late inspiratory neurons, but no changes were observed in the ramp-inspiratory and post-inspiratory neurons. This imbalance in the respiratory network might contribute to the modulation of sympathetic activity after SAD.
ABSTRACT
In previous studies, we documented that after sino-aortic denervation (SAD) in rats there are significant changes in the breathing pattern, but no significant changes in sympathetic activity and mean arterial pressure compared with sham-operated rats. However, the neural mechanisms involved in the respiratory changes after SAD and the extent to which they might contribute to the observed normal sympathetic activity and mean arterial pressure remain unclear. Here, we hypothesized that after SAD, rats present with changes in the firing frequency of the ventral medullary inspiratory and post-inspiratory neurons. To test this hypothesis, male Wistar rats underwent SAD or sham surgery and 3 days later were surgically prepared for an in situ experiment. The duration of inspiration significantly increased in SAD rats. During inspiration, the total firing frequency of ramp-inspiratory, pre-inspiratory/inspiratory and late-inspiratory neurons was not different between groups. During post-inspiration, the total firing frequency of post-inspiratory neurons was also not different between groups. Furthermore, the data demonstrate a reduced interburst frequency of pre-inspiratory/inspiratory neurons and an increased long-term variability of late-inspiratory neurons in SAD compared with sham-operated rats. These findings indicate that the SAD-induced prolongation of inspiration was not accompanied by alterations in the total firing frequency of the ventral medullary respiratory neurons, but it was associated with changes in the long-term variability of late-inspiratory neurons. We suggest that the timing imbalance in the respiratory network in SAD rats might contribute to the modulation of presympathetic neurons after removal of baroreceptor afferents.
Topics: Animals; Aorta; Arterial Pressure; Hypertension; Male; Neurons; Pressoreceptors; Rats, Wistar; Respiration; Sympathetic Nervous System
PubMed: 30427561
DOI: 10.1113/EP087150