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Science (New York, N.Y.) Feb 2024The transmission of the heartbeat through the cerebral vascular system causes intracranial pressure pulsations. We discovered that arterial pressure pulsations can...
The transmission of the heartbeat through the cerebral vascular system causes intracranial pressure pulsations. We discovered that arterial pressure pulsations can directly modulate central neuronal activity. In a semi-intact rat brain preparation, vascular pressure pulsations elicited correlated local field oscillations in the olfactory bulb mitral cell layer. These oscillations did not require synaptic transmission but reflected baroreceptive transduction in mitral cells. This transduction was mediated by a fast excitatory mechanosensitive ion channel and modulated neuronal spiking activity. In awake animals, the heartbeat entrained the activity of a subset of olfactory bulb neurons within ~20 milliseconds. Thus, we propose that this fast, intrinsic interoceptive mechanism can modulate perception-for example, during arousal-within the olfactory bulb and possibly across various other brain areas.
Topics: Animals; Rats; Blood Pressure; Ion Channels; Neurons; Olfactory Bulb; Synaptic Transmission; Mechanotransduction, Cellular; Pressoreceptors; Rats, Wistar; Male; Mice; Mice, Inbred C57BL; Heart Rate; Pulse; Brain; Intracranial Pressure; Female
PubMed: 38301001
DOI: 10.1126/science.adk8511 -
Hypertension (Dallas, Tex. : 1979) Jan 2022
Topics: Baroreflex; Blood Pressure; Pressoreceptors
PubMed: 34878899
DOI: 10.1161/HYPERTENSIONAHA.121.18372 -
Current Cardiology Reports Sep 2019Sympathetic overactivity plays an important role in the progression of pulmonary arterial hypertension (PAH). The purpose of this review is to illustrate localization of... (Review)
Review
PURPOSE OF REVIEW
Sympathetic overactivity plays an important role in the progression of pulmonary arterial hypertension (PAH). The purpose of this review is to illustrate localization of pulmonary arterial sympathetic nerves, the key steps of pulmonary artery denervation (PADN) procedure, and to highlight clinical outcomes.
RECENT FINDINGS
Sympathetic nerves mostly occurred in the posterior region of the bifurcation and pulmonary trunk. Emerging preclinical data provided the potential of PADN for PAH. PADN, produced at bifurcation area, improved a profound reduction of pulmonary arterial pressure and ameliorated clinical outcomes with an exclusive ablation catheter. The application of PADN in the patients of PAH or combined pre-capillary and post-capillary PH (CpcPH) improved the hemodynamic parameters and increased 6MWD. Sympathetic overactivity aggravates PAH. PADN is a promising interventional treatment for PAH and CpcPH. Additional clinical trials are warranted to confirm the efficacy of PADN.
Topics: Denervation; Hemodynamics; Humans; Hypertension, Pulmonary; Pressoreceptors; Pulmonary Arterial Hypertension; Pulmonary Artery; Sympathectomy; Sympathetic Nervous System; Treatment Outcome
PubMed: 31486924
DOI: 10.1007/s11886-019-1203-z -
JACC. Clinical Electrophysiology Feb 2022This study sought to evaluate the role of cardiac afferent reflexes in atrial fibrillation (AF).
OBJECTIVES
This study sought to evaluate the role of cardiac afferent reflexes in atrial fibrillation (AF).
BACKGROUND
Efferent autonomic tone is not associated with atrial remodeling and AF persistence. However, the role of cardiac afferents is unknown.
METHODS
Individuals with nonpermanent AF (n = 48) were prospectively studied (23 in the in-AF group and 25 in sinus rhythm [SR]) with 12 matched control subjects. We performed: 1) low-level lower body negative pressure (LBNP), which decreases cardiac volume, offloading predominantly cardiac afferent (volume-sensitive) low-pressure baroreceptors; 2) Valsalva reflex (predominantly arterial high-pressure baroreceptors); and 3) isometric handgrip reflex (both baroreceptors). We measured beat-to-beat mean arterial pressure (MAP) and heart rate (HR). LBNP elicits reflex vasoconstriction, estimated using venous occlusion plethysmography-derived forearm blood flow (∝1/vascular resistance), maintaining MAP. To assess reversibility, we repeated LBNP (same day) after 1-hour low-level tragus stimulation (in n = 5 in the in-AF group and n = 10 in the in-SR group) and >6 weeks post-cardioversion (n = 7).
RESULTS
The 3 groups were well matched for age (59 ± 12 years, 83% male), body mass index, and risk factors (P = NS). The in-AF group had higher left atrial volume (P < 0.001) and resting HR (P = 0.01) but similar MAP (P = 0.7). The normal LBNP vasoconstriction (-49 ± 5%) maintaining MAP (control subjects) was attenuated in the in-SR group (-12 ± 9%; P = 0.005) and dysfunctional in the in-AF group (+11 ± 6%; P < 0.001), in which MAP decreased and HR was unchanged. Valsalva was normal throughout. Handgrip MAP response was lowest in the in-AF group (P = 0.01). Interestingly, low-level tragus stimulation and cardioversion improved LBNP vasoconstriction (-48 ± 15%; P = 0.04; and -32 ± 9%; P = 0.02, respectively).
CONCLUSIONS
Cardiac afferent (volume-sensitive) reflexes are abnormal in AF patients during SR and dysfunctional during AF. This could contribute to AF progression, thus explaining "AF begets AF." (Characterisation of Autonomic function in Atrial Fibrillation [AF-AF Study]; ACTRN12619000186156).
Topics: Aged; Atrial Fibrillation; Female; Hand Strength; Heart Atria; Humans; Lower Body Negative Pressure; Male; Middle Aged; Pressoreceptors
PubMed: 35210071
DOI: 10.1016/j.jacep.2021.10.010 -
Nutrients Feb 2022For normal maintenance of blood pressure and blood volume a well-balanced renin-angiotensin-aldosterone system (RAS) is necessary. For this purpose, renin is secreted as... (Review)
Review
For normal maintenance of blood pressure and blood volume a well-balanced renin-angiotensin-aldosterone system (RAS) is necessary. For this purpose, renin is secreted as the situation demands by the juxtaglomerular cells (also called as granular cells) that are in the walls of the afferent arterioles. Juxtaglomerular cells can sense minute changes in the blood pressure and blood volume and accordingly synthesize, store, and secrete appropriate amounts of renin. Thus, when the blood pressure and blood volume are decreased JGA cells synthesize and secrete higher amounts of renin and when the blood pressure and blood volume is increased the synthesis and secretion of renin is decreased such that homeostasis is restored. To decipher this important function, JGA cells (renin cells) need to sense and transmit the extracellular physical forces to their chromatin to control renin gene expression for appropriate renin synthesis. The changes in perfusion pressure are sensed by Integrin β1 that is transmitted to the renin cell's nucleus via lamin A/C that produces changes in the architecture of the chromatin. This results in an alteration (either increase or decrease) in renin gene expression. Cell membrane is situated in an unique location since all stimuli need to be transmitted to the cell nucleus and messages from the DNA to the cell external environment can be conveyed only through it. This implies that cell membrane structure and integrity is essential for all cellular functions. Cell membrane is composed to proteins and lipids. The lipid components of the cell membrane regulate its (cell membrane) fluidity and the way the messages are transmitted between the cell and its environment. Of all the lipids present in the membrane, arachidonic acid (AA) forms an important constituent. In response to pressure and other stimuli, cellular and nuclear shape changes occur that render nucleus to act as an elastic mechanotransducer that produces not only changes in cell shape but also in its dynamic behavior. Cell shape changes in response to external pressure(s) result(s) in the activation of cPLA2 (cytosolic phospholipase 2)-AA pathway that stretches to recruit myosin II which produces actin-myosin cytoskeleton contractility. Released AA can undergo peroxidation and peroxidized AA binds to DNA to regulate the expression of several genes. Alterations in the perfusion pressure in the afferent arterioles produces parallel changes in the renin cell membrane leading to changes in renin release. AA and its metabolic products regulate not only the release of renin but also changes in the vanilloid type 1 (TRPV1) expression in renal sensory nerves. Thus, AA and its metabolites function as intermediate/mediator molecules in transducing changes in perfusion and mechanical pressures that involves nuclear mechanotransduction mechanism. This mechanotransducer function of AA has relevance to the synthesis and release of insulin, neurotransmitters, and other soluble mediators release by specialized and non-specialized cells. Thus, AA plays a critical role in diseases such as diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, sepsis, lupus, rheumatoid arthritis, and cancer.
Topics: Arachidonic Acid; Juxtaglomerular Apparatus; Mechanotransduction, Cellular; Pressoreceptors; Renin
PubMed: 35215399
DOI: 10.3390/nu14040749 -
Autonomic Neuroscience : Basic &... Nov 2019Autonomic nervous system (ANS) has been extensively explored in obstructive sleep apnea (OSA). Autonomic alterations in these patients have been described by means of... (Review)
Review
Autonomic nervous system (ANS) has been extensively explored in obstructive sleep apnea (OSA). Autonomic alterations in these patients have been described by means of several methods, evaluating ANS function both directly with microneurography and indirectly through baroreflex sensitivity (BRS, by the sequence method or the cross-spectral approach), heart rate variability analysis (HRV, both in the time and frequency domain) during sleep and wake, or conventional laboratory tests, including cold pressor test, hand grip test or measurement of urinary cathecolamine excretion. Several studies in OSA patients have shown ANS alterations, in particular sympathetic overactivity, both acutely during apnea events and chronically during the daytime, being both also involved in cardiovascular consequences of sleep disordered breathing. The association between OSA and sympathetic dysregulation suggests a dose response relationship between OSA severity and the degree of sympathetic overactivity and this association seems to be reversible as the treatment of OSA is implemented. Additionally ANS is involved in regulating visceral and humoral functions to maintain the body homeostasis and in reaction and adaptation to external and internal stressor stimuli. However, the vast majority of studies have focussed on cardiovascular alterations, which are easier to measure, somewhat neglecting the other functions regulated by ANS. More evidence is therefore needed to better characterize the impact that sleep disorder breathing may have on ANS both in the short and long term.
Topics: Adaptation, Physiological; Autonomic Nervous System; Autonomic Nervous System Diseases; Baroreflex; Cardiovascular Diseases; Catecholamines; Continuous Positive Airway Pressure; Female; Gastrointestinal Diseases; Heart Rate; Humans; Male; Polysomnography; Pressoreceptors; Reflex, Abnormal; Sexual Dysfunction, Physiological; Sleep Apnea, Obstructive; Sleepiness; Urination Disorders
PubMed: 31445406
DOI: 10.1016/j.autneu.2019.102563 -
Respiratory Physiology & Neurobiology Sep 2022Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms... (Review)
Review
Cough, the main airway defensive process, is modulated by multiple sensory inputs from the respiratory system and outside of it. This modulation is one of the mechanisms that contributes to the sensitization of cough pathways at the peripheral and/or central level via neuroplasticity and it manifests most often as augmented coughing. Cardiorespiratory coupling is an important mechanism responsible for a match between oxygenation and cardiac output and bidirectional relationships exist between respiration and cardiovascular function. While the impact of cough with the robust swings of the intrathoracic pressure on haemodynamic parameters and heart electrophysiology are well characterized, little is known about the modulation of cough by haemodynamic parameters - mainly the blood pressure. Some circumstantial findings from older animal studies and more recent sophisticated analysis confirm that baroreceptor stimulation and unloading alters coughing evoked in experiments. Clinical relevance of such findings is not presently known.
Topics: Animals; Baroreflex; Blood Pressure; Cardiac Output; Cough; Heart Rate; Pressoreceptors; Respiration
PubMed: 35595217
DOI: 10.1016/j.resp.2022.103921 -
Hypertension (Dallas, Tex. : 1979) May 2023
Topics: Humans; Baroreflex; COVID-19; Pressoreceptors; Sympathetic Nervous System; Blood Pressure; Afferent Pathways
PubMed: 36802914
DOI: 10.1161/HYPERTENSIONAHA.123.20316 -
Expert Review of Medical Devices Dec 2019: Resistant hypertension is characterized by an hyperadrenergic tone and by a neurohumoral activation. In this condition drug therapies are unable to obtain a good... (Review)
Review
: Resistant hypertension is characterized by an hyperadrenergic tone and by a neurohumoral activation. In this condition drug therapies are unable to obtain a good control of blood pressure and therefore need a contribution from non-pharmachological approach. To this aim it has been hypothesized that to lower blood pressure this could be obtained through stimulation of carotid baroreceptors and modulation of the adrenergic tone.: several studies and trials have evaluated the safety and efficacy of two devices-based therapies and this review will discuss the research obtained mainly in resistant hypertensive subjects.: the studies performed have clearly shown the safety and efficacy of these approaches. The stimulation of carotid baroreceptors induces a significant reduction in blood pressure values associated with a reduction in adrenergic tone. The two systems have same limitations. While baroreflex activation therapy has been upgraded to a more simple system, an upgrade of endovascular baroreflex amplification will be able to reduce the side effects. Due to the fact that neurohumoral activation and hyperadrenergic tone are present in several pathophysiological conditions it is possible to assume a wider use of these systems in the future.
Topics: Baroreflex; Electric Stimulation Therapy; Humans; Hypertension; Pressoreceptors; Sympathetic Nervous System
PubMed: 31774336
DOI: 10.1080/17434440.2019.1697230 -
Advances in Physiology Education Jun 2022While the effects of changing heart rate and systemic vascular resistance have been generally understood and appreciated, the effects of changes in left ventricular... (Review)
Review
While the effects of changing heart rate and systemic vascular resistance have been generally understood and appreciated, the effects of changes in left ventricular contractility on end-systolic volume may have been less understood and appreciated and the effects of changes in venous capacitance on end-diastolic volume may have been unknown to many readers. Herein, we have provided a brief review for the medical student and beginning graduate student highlighting these sometimes-complex relationships.
Topics: Blood Pressure; Heart Rate; Heart Ventricles; Humans; Pressoreceptors; Vascular Resistance
PubMed: 35201919
DOI: 10.1152/advan.00160.2021