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PloS One 2020Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb,...
Ectotherms may experience large body temperature (Tb) variations. Higher Tb have been reported to increase baroreflex sensitivity in ectotherm tetrapods. At lower Tb, pulse interval (PI) increases and diastolic pressure decays for longer, possibly resulting in lower end-diastolic pressures and mean arterial pressures (Pm). Additionally, compensatory baroreflex-related heart rate modulation (i.e. the cardiac branch of the baroreflex response) is delayed due to increased PI. Thus, low Tb is potentially detrimental, leading to cardiovascular malfunctioning. This raises the question on how Pm is regulated in such an adverse condition. We investigated the baroreflex compensations that enables tegu lizards, Salvator merianae, to maintain blood pressure homeostasis in a wide Tb range. Lizards had their femoral artery cannulated and pressure signals recorded at 15°C, 25°C and 35°C. We used the sequence method to analyse the heart rate baroreflex-related corrections to spontaneous pressure fluctuations at each temperature. Vascular adjustments (i.e. the peripheral branch) were assessed by calculating the time constant for arterial pressure decay (τ)-resultant from the action of both vascular resistance and compliance-by fitting the diastolic pressure descent to the two-element Windkessel equation. We observed that at lower Tb, lizards increased baroreflex gain at the operating point (Gop) and τ, indicating that the diastolic pressure decays at a slower rate. Gop normalized to Pm and PI, as well as the ratio τ/PI, did not change, indicating that both baroreflex gain and rate of pressure decay are adjusted according to PI lengthening. Consequently, pressure parameters and the oscillatory power fraction (an index of wasted cardiac energy) were unaltered by Tb, indicating that both Gop and τ modulation are crucial for cardiovascular homeostasis.
Topics: Animals; Baroreflex; Blood Pressure; Body Temperature; Body Temperature Regulation; Heart Rate; Lizards; Pressoreceptors
PubMed: 33227002
DOI: 10.1371/journal.pone.0242346 -
JCI Insight Oct 2020The spontaneously hypertensive rat (SHR) is a genetic model of primary hypertension with an etiology that includes sympathetic overdrive. To elucidate the neurogenic...
The spontaneously hypertensive rat (SHR) is a genetic model of primary hypertension with an etiology that includes sympathetic overdrive. To elucidate the neurogenic mechanisms underlying the pathophysiology of this model, we analyzed the dynamic baroreflex response to spontaneous fluctuations in arterial pressure in conscious SHRs, as well as in the Wistar-Kyoto (WKY), the Dahl salt-sensitive, the Dahl salt-resistant, and the Sprague-Dawley rat. Observations revealed the existence of long intermittent periods (lasting up to several minutes) of engagement and disengagement of baroreflex control of heart rate. Analysis of these intermittent periods revealed a predictive relationship between increased mean arterial pressure and progressive baroreflex disengagement that was present in the SHR and WKY strains but absent in others. This relationship yielded the hypothesis that a lower proportion of engagement versus disengagement of the baroreflex in SHR compared with WKY contributes to the hypertension (or increased blood pressure) in SHR compared with WKY. Results of experiments using sinoaortic baroreceptor denervation were consistent with the hypothesis that dysfunction of the baroreflex contributes to the etiology of hypertension in the SHR. Thus, this study provides experimental evidence for the roles of the baroreflex in long-term arterial pressure regulation and in the etiology of primary hypertension in this animal model.
Topics: Animals; Baroreflex; Blood Pressure; Female; Heart Rate; Hypertension; Male; Pressoreceptors; Rats; Rats, Inbred Dahl; Rats, Inbred SHR; Rats, Inbred WKY; Rats, Sprague-Dawley; Sodium Chloride, Dietary
PubMed: 33004690
DOI: 10.1172/jci.insight.139789 -
FASEB Journal : Official Publication of... Nov 2020This study was designed to clarify whether the irradiation of carotid baroreceptor (CB) with low-intensity pulsed ultrasound (LIPUS) protects against obesity by...
Irradiation of carotid baroreceptor with low-intensity pulsed ultrasound exerts different metabolic protection in perirenal, epididymal white adipose tissue and interscapular brown adipose tissue of obese rats.
This study was designed to clarify whether the irradiation of carotid baroreceptor (CB) with low-intensity pulsed ultrasound (LIPUS) protects against obesity by rebalancing the autonomic nervous system (ANS). Obesity was induced using a high-fat diet (HFD) for 8 weeks in Sprague-Dawley rats. Irradiation with LIPUS was daily (20 minutes a day) applied to the right CB. In our study, LIPUS significantly ameliorated metabolic disorders in obese rats. LIPUS partly restored norepinephrine (NE) and acetylcholine (ACH) levels in the perirenal white adipose tissue (PWAT), epididymal white adipose tissue (EWAT), interscapular brown adipose tissue (IBAT), and plasma of obese rats. LIPUS partially rectified the dysregulated AMP-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor (PPAR) α/ɣ pathway in the PWAT, EWAT, and IBAT of obese rats. PPARγ and PPARγ target genes respond more sensitively to HFD and LIPUS in PWAT and EWAT than in IBAT. NE, ACH, uncoupling protein-1, phosphorylated AMPK, PPARα, and PPARα target genes respond more sensitively to HFD and LIPUS in IBAT than in PWAT and EWAT. Conclusion: LIPUS irradiation of CB exerts different metabolic protection in PWAT, EWAT, and IBAT by rebalancing the ANS and rectifying the AMPK/PPARα/ɣ pathway in obese rats.
Topics: Adipose Tissue, Brown; Adipose Tissue, White; Animals; Carotid Sinus; Diet, High-Fat; Epididymis; Male; Metabolic Diseases; Obesity; Pressoreceptors; Rats; Rats, Sprague-Dawley; Ultrasonic Waves
PubMed: 32954572
DOI: 10.1096/fj.202001550R -
Seminars in Neurology Oct 2020Head and neck tumors can affect afferent baroreceptor neurons and either interrupt or intermittently increase their signaling, causing blood pressure to become erratic....
Head and neck tumors can affect afferent baroreceptor neurons and either interrupt or intermittently increase their signaling, causing blood pressure to become erratic. When the afferent fibers of the baroreflex are injured by surgery or radiotherapy or fail to develop as in familial dysautonomia, their sensory information is no longer present to regulate arterial blood pressure, resulting in afferent baroreflex failure. When the baroreflex afferents are abnormally activated, such as by paragangliomas in the neck, presumably by direct compression, they trigger acute hypotension and bradycardia and frequently syncope, by a mechanism similar to the carotid sinus syndrome. We describe our observations in a large series of 23 patients with afferent baroreflex dysfunction and the cardiovascular autonomic features that arise when the sensory baroreceptor neurons are injured or compressed. The management of afferent baroreceptor dysfunction is limited, but pharmacological strategies can mitigate blood pressure swings, improve symptoms, and may reduce hypertensive organ damage. Although rare, the prevalence of afferent baroreflex dysfunction appears to be increasing in middle-aged men due to human papillomavirus related oropharyngeal cancer.
Topics: Autonomic Nervous System Diseases; Baroreflex; Cardiovascular Diseases; Head and Neck Neoplasms; Humans; Male; Middle Aged; Neurons, Afferent; Phenotype; Pressoreceptors; Signal Transduction
PubMed: 32906172
DOI: 10.1055/s-0040-1713892 -
Nutrients Aug 2020Studies suggest that migraine pain has a vascular component. The prevailing dogma is that peripheral vasoconstriction activates baroreceptors in central, large arteries.... (Review)
Review
Studies suggest that migraine pain has a vascular component. The prevailing dogma is that peripheral vasoconstriction activates baroreceptors in central, large arteries. Dilatation of central vessels stimulates nociceptors and induces cortical spreading depression. Studies investigating nitric oxide (NO) donors support the indicated hypothesis that pain is amplified when acutely administered. In this review, we provide an alternate hypothesis which, if substantiated, may provide therapeutic opportunities for attenuating migraine frequency and severity. We suggest that in migraines, heightened sympathetic tone results in progressive central microvascular constriction. Suboptimal parenchymal blood flow, we suggest, activates nociceptors and triggers headache pain onset. Administration of NO donors could paradoxically promote constriction of the microvasculature as a consequence of larger upstream central artery vasodilatation. Inhibitors of NO production are reported to alleviate migraine pain. We describe how constriction of larger upstream arteries, induced by NO synthesis inhibitors, may result in a compensatory dilatory response of the microvasculature. The restoration of central capillary blood flow may be the primary mechanism for pain relief. Attenuating the propensity for central capillary constriction and promoting a more dilatory phenotype may reduce frequency and severity of migraines. Here, we propose consideration of two dietary nutraceuticals for reducing migraine risk: L-arginine and aged garlic extracts.
Topics: Arginine; Cerebral Arteries; Dietary Supplements; Garlic; Humans; Microvessels; Migraine Disorders; Nitric Oxide; Nitric Oxide Donors; Nociceptors; Plant Extracts; Pressoreceptors; Severity of Illness Index; Vasoconstriction; Vasodilation
PubMed: 32824835
DOI: 10.3390/nu12082487 -
Diabetes & Metabolic Syndrome 2020The present study compared cardiovascular autonomic activity and reactivity during fasting (FS) and hyperglycemia (HS) states in young healthy females. (Comparative Study)
Comparative Study
BACKGROUND AND AIM
The present study compared cardiovascular autonomic activity and reactivity during fasting (FS) and hyperglycemia (HS) states in young healthy females.
METHODS
This case crossover study was conducted on 30 females recruited by convenient sampling. Blood glucose levels were measured in FS and after oral glucose load i.e., HS. Finger arterial blood pressure (BP) and ECG were recorded constantly to monitor baroreceptor sensitivity (BRS) and heart rate variability (HRV). Autonomic reactivity was tested with deep breathing (DB), Valsalva manoeuvre (VM), and head-up-tilt (HUT) test under FS and HS. HRV parameters not normally distributed were natural log (ln) transformed.
RESULTS
Significantly reduced Valsalva ratio and higher heart rate and BP were observed in HS that continued during HUT (P < 0.05). The lnSDNN (standard deviation of normal-to-normal intervals) and lnRMSSD (root mean square of successive differences) were significantly lower (p < 0.05) in HS during HUT. After HUT, lnRMSSD remained lower (P = 0.031), whereas lnLF/HF (low frequency/high frequency power) ratio (P = 0.042) and LFnu (normalized units) (P = 0.024) were higher in HS. BRS was significantly lower in supine position in HS compared to FS and further reduced in HUT position in both FS and HS (P < 0.05).
CONCLUSION
Compared to FS, the HS exhibited heightened sympathetic activity with attenuation of parasympathetic activity and this phenomenon was further accentuated by HUT. BRS was more sensitive indicator of autonomic effects of hyperglycemia in resting state. In addition to standard tests, autonomic reactivity in vulnerable young subjects could be useful to detect autonomic imbalance at an early stage.
Topics: Adult; Autonomic Nervous System; Biomarkers; Blood Pressure; Cardiovascular System; Cross-Over Studies; Fasting; Female; Follow-Up Studies; Heart Rate; Humans; Hyperglycemia; Pressoreceptors; Prognosis; Young Adult
PubMed: 32795743
DOI: 10.1016/j.dsx.2020.07.035 -
Neuroscience Aug 2020Large conductance of Ca-activated K channel (KCa1.1) plays an inhibitory role in neuroexcitation. However, the expression of KCNMB4/β4-subunit in the nodose ganglia...
Large conductance of Ca-activated K channel (KCa1.1) plays an inhibitory role in neuroexcitation. However, the expression of KCNMB4/β4-subunit in the nodose ganglia (NG) and nucleus tractus solitarius (NTS), and its effect and regulation on baroreflex afferent function at post-transcriptional level of female rats remains unknown. Here, we demonstrated that the expression of β4-subunit encoded by KCNMB4 was significantly lower in females vs. males and ovariectomized (OVX) rats in the NG. Although all baroreceptor neurons (BRNs) expressed β4-subunit, altered discharge characteristics were only observed in Ah-type neurons after ovariectomy. Notably, the decreased excitability of Ah-types was restored by paxilline and further enhanced by iberiotoxin. The consistent changes were observed in excitatory post-synaptic currents. The level of miR-504 was higher in females, which was predicted to bind to the 3'UTR of KCNMB4. In consistent, an inverse expression pattern between miR-504 and KCNMB4 was observed in baroreflex afferents. The paxilline-sensitive β4-subunits is less in Ah-types and up-regulated by ovariectomy. These data indicated that KCa1.1 β4-subunit is the key regulator in neuroexcitation of Ah-types and sexual-dimorphism in baroreflex afferent function through estrogen-dependent inhibition of KCNMB4 expression via miR-504.
Topics: Afferent Pathways; Animals; Baroreflex; Estrogens; Female; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Large-Conductance Calcium-Activated Potassium Channel beta Subunits; Male; MicroRNAs; Nerve Tissue Proteins; Pressoreceptors; Rats
PubMed: 32653540
DOI: 10.1016/j.neuroscience.2020.07.003 -
American Journal of Physiology. Heart... Aug 2020Changes in the arterial baroreflex arc contribute to elevated sympathetic outflow and altered reflex control of blood pressure with human aging. Using ultrasound and... (Comparative Study)
Comparative Study
Changes in the arterial baroreflex arc contribute to elevated sympathetic outflow and altered reflex control of blood pressure with human aging. Using ultrasound and sympathetic microneurography (muscle sympathetic nerve activity, MSNA) we investigated the relationships between aortic and carotid artery wall tension (indices of baroreceptor activation) and the vascular sympathetic baroreflex operating point (OP; MSNA burst incidence) in healthy, normotensive young ( = 27, 23 ± 3 yr) and middle-aged men ( = 22, 55 ± 4 yr). In young men, the OP was positively related to the magnitude and rate of unloading and time spent unloaded in the aortic artery ( = 0.56, 0.65, and 0.51, = 0.02, 0.003, and 0.03), but not related to the magnitude or rate of unloading or time spent unloaded in the carotid artery ( = -0.32, -0.07, and 0.06, = 0.25, 0.81, and 0.85). In contrast, in middle-aged men, the OP was not related to either the magnitude or rate of unloading or time spent unloaded in the aortic ( = 0.22, 0.21, and 0.27, = 0.41, 0.43, and 0.31) or carotid artery ( = 0.06, 0.28, and -0.01; = 0.48, 0.25, and 0.98). In conclusion, in young men, aortic unloading mechanics may play a role in determining the vascular sympathetic baroreflex OP. In contrast, in middle-aged men, barosensory vessel unloading mechanics do not appear to determine the vascular sympathetic baroreflex OP and, therefore, do not contribute to age-related arterial baroreflex resetting and increased resting MSNA. We assessed the influence of barosensory vessel mechanics (magnitude and rate of unloading and time spent unloaded) as a surrogate for baroreceptor unloading. In young men, aortic unloading mechanics are important in regulating the operating point of the vascular sympathetic baroreflex, whereas in middle-aged men, these arterial mechanics do not influence this operating point. The age-related increase in resting muscle sympathetic nerve activity does not appear to be driven by altered baroreceptor input from stiffer barosensory vessels.
Topics: Adult; Age Factors; Aging; Aorta; Arterial Pressure; Baroreflex; Carotid Arteries; Heart Rate; Homeostasis; Humans; Male; Middle Aged; Muscle, Skeletal; Pressoreceptors; Time Factors; Ultrasonography; Young Adult
PubMed: 32648822
DOI: 10.1152/ajpheart.00265.2020 -
The Journal of Clinical Investigation Jul 2020The baroreceptor reflex is a powerful neural feedback that regulates arterial pressure (AP). Mechanosensitive channels transduce pulsatile AP to electrical signals in...
The baroreceptor reflex is a powerful neural feedback that regulates arterial pressure (AP). Mechanosensitive channels transduce pulsatile AP to electrical signals in baroreceptors. Here we show that tentonin 3 (TTN3/TMEM150C), a cation channel activated by mechanical strokes, is essential for detecting AP changes in the aortic arch. TTN3 was expressed in nerve terminals in the aortic arch and nodose ganglion (NG) neurons. Genetic ablation of Ttn3 induced ambient hypertension, tachycardia, AP fluctuations, and impaired baroreflex sensitivity. Chemogenetic silencing or activation of Ttn3+ neurons in the NG resulted in an increase in AP and heart rate, or vice versa. More important, overexpression of Ttn3 in the NG of Ttn3-/- mice reversed the cardiovascular changes observed in Ttn3-/- mice. We conclude that TTN3 is a molecular component contributing to the sensing of dynamic AP changes in baroreceptors.
Topics: Animals; Aorta, Thoracic; Blood Pressure; HEK293 Cells; Humans; Hypertension; Membrane Proteins; Mice; Mice, Knockout; Neurons; Nodose Ganglion; Pressoreceptors; Tachycardia
PubMed: 32484458
DOI: 10.1172/JCI133798 -
The Journal of Clinical Investigation Jul 2020Mechanical stretch of baroreceptors in the wall of the aortic arch and carotid sinus initiates autonomic reflexes to change heart rate and blood pressure for...
Mechanical stretch of baroreceptors in the wall of the aortic arch and carotid sinus initiates autonomic reflexes to change heart rate and blood pressure for cardiovascular homeostasis. In this issue of the JCI, Lu et al. show that tentonin 3 (TTN3), a recently identified stretch-sensitive ion channel, was present at the vagus afferent nerve endings innervating the aortic arch to function as a baroreceptor. This study expands the molecular profiles of baroreceptors and provides new insights into molecular mechanisms underlying the regulation of cardiovascular functions through baroreceptor function.
Topics: Aorta, Thoracic; Blood Pressure; Carotid Sinus; Ion Channels; Pressoreceptors
PubMed: 32484454
DOI: 10.1172/JCI138120