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Applied Physiology, Nutrition, and... Oct 2020Numerous studies have examined heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) variables during recovery both acutely (under 3 h) and long-term... (Randomized Controlled Trial)
Randomized Controlled Trial
Numerous studies have examined heart rate variability (HRV) and cardiac baroreceptor sensitivity (BRS) variables during recovery both acutely (under 3 h) and long-term (24, 48, and 72 h) postexercise. However, there is little literature examining HRV and BRS measures between these timepoints. Spontaneous short-term HRV and cardiac BRS measures were collected in 9 participants before and at zero, 1, 2, 4, 6, and 8 h after 3 separate conditions: moderate-intensity continuous exercise (MICE; 45 min at 50% heart rate reserve), high-intensity interval exercise (HIIE; 25 min including ten 1-min intervals at 85% heart rate reserve), and control (30 min quiet rest). HRV measures in the time domain were only affected immediately following HIIE and MICE at hour zero (all < 0.043), whereas frequency-domain metrics were unaltered (all > 0.102). These measures were highly consistent across the control day (all > 0.420). Cardiac BRS was assessed via low-frequency (LF) gain, and revealed reductions following HIIE at hour zero ( < 0.012). Cardiac BRS LF gain remained consistent following MICE and control interventions (all > 0.280). The common practice of waiting 12 to 24 h is overly conservative as the current findings demonstrate measures return to baseline at ∼60 min after exercise. Moreover, these metrics demonstrated high levels of within- and between-day reliability. Previously a 12-h minimum restriction from exercise was required before participation in HRV/BRS studies. Recovery from moderate-intensity exercise for HRV and BRS metrics was <60 min; whereas, high-intensity intervals led to alterations for approximately 60 min. Spontaneous HRV and cardiac BRS demonstrated high levels of within-day reproducibility.
Topics: Adult; Baroreflex; Cohort Studies; Cross-Over Studies; Female; Heart Rate; High-Intensity Interval Training; Humans; Male; Pressoreceptors; Reproducibility of Results; Time
PubMed: 32343909
DOI: 10.1139/apnm-2019-0810 -
Hypertension (Dallas, Tex. : 1979) Jun 2020Nighttime blood pressure (BP) generally dips by 10% to 20% of the daytime values, and abnormal BP dipping may affect vascular health independently of BP level. The...
Nighttime blood pressure (BP) generally dips by 10% to 20% of the daytime values, and abnormal BP dipping may affect vascular health independently of BP level. The regulation of BP dipping involves arterial baroreflex, whose receptors mainly reside in carotid sinuses and aortic arch. Atherosclerosis in these baroreceptor-resident arteries (BRAs) is frequent among patients with ischemic stroke (IS) and might impair their BP-regulating capacity. We aimed to examine associations between atherosclerosis of BRA and BP dipping in patients with IS. BP dipping ratio was measured by 24-hour ambulatory blood pressure monitoring on the sixth day after IS. With computed tomography angiography, atherosclerosis conditions in 10 segments of carotid sinuses and aortic arch were scored and summed as total atherosclerosis burden of BRA. Among the 245 patients with IS, 78.0% had atherosclerosis in BRA. The total AS burden of BRA was negatively correlated with systolic BP dipping ratio (=-0.331; <0.001) and diastolic BP dipping ratio (=-0.225; <0.001). After adjusting for age, sex, vascular risk factors, 24-hour BP means, cervical and intracranial atherosclerosis scores, the negative correlations still existed (adjusted β, -0.259 [95% CI, -0.416 to -0.102] and adjusted β, -0.178 [95% CI, -0.346 to -0.010], respectively). In conclusion, higher total atherosclerosis burden of BRA was independently indicative of more blunted dipping of systolic BP and diastolic BP in IS. The total atherosclerosis burden of BRA might be important for predicting and managing BP dipping in patients with IS.
Topics: Aged; Aorta, Thoracic; Atherosclerosis; Blood Pressure Monitoring, Ambulatory; Carotid Sinus; Computed Tomography Angiography; Correlation of Data; Female; Heart Disease Risk Factors; Humans; Hypotension; Ischemic Stroke; Male; Pressoreceptors; Severity of Illness Index
PubMed: 32336234
DOI: 10.1161/HYPERTENSIONAHA.120.15036 -
BMJ Case Reports Dec 2021We present a case of a 77-year-old man who reported 5 months of syncopal episodes. He was found to have diffuse large B-cell lymphoma encasing the left internal...
We present a case of a 77-year-old man who reported 5 months of syncopal episodes. He was found to have diffuse large B-cell lymphoma encasing the left internal carotid artery but not impeding blood flow. The syncopal episodes resolved after his first cycle of chemotherapy. Recurrent syncope in non-cardiac lymphomas and other head and neck masses is exceedingly rare and may be due to reflex syncope prompted by carotid baroreceptor activation. There are 11 previously described cases of recurrent syncope associated with non-cardiac lymphoma. In all cases, lymphadenopathy abutting the carotid artery was present and the syncopal episodes resolved with treatment. Our case illustrates that malignancy should be considered in patients with unexplained recurrent syncope.
Topics: Aged; Carotid Artery, Internal; Humans; Lymphoma, Large B-Cell, Diffuse; Male; Neoplasm Recurrence, Local; Pressoreceptors; Syncope
PubMed: 34969790
DOI: 10.1136/bcr-2021-244881 -
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 -
International Journal of Environmental... Oct 2021This paper presents data from a transcutaneous vagus nerve stimulation experiment that point towards a blunted cardiac baroreceptor sensitivity (cBRS) in young males...
Men Show Reduced Cardiac Baroreceptor Sensitivity during Modestly Painful Electrical Stimulation of the Forearm: Exploratory Results from a Sham-Controlled Crossover Vagus Nerve Stimulation Study.
This paper presents data from a transcutaneous vagus nerve stimulation experiment that point towards a blunted cardiac baroreceptor sensitivity (cBRS) in young males compared to females during electrical stimulation of the forearm and a rhythmic breathing task. Continuous electrocardiography, impedance cardiography and continuous blood-pressure recordings were assessed in a sex-matched cohort of twenty young healthy subjects. Electrical stimulation of the median nerve was conducted by using a threshold-tracking method combined with two rhythmic breathing tasks (0.1 and 0.2 Hz) before, during and after active or sham transcutaneous vagus nerve stimulation. Autonomic and hemodynamic parameters were calculated, and differences were analyzed by using linear mixed models and post hoc F-tests. None of the autonomic and hemodynamic parameters differed between the sham and active conditions. However, compared to females, male participants had an overall lower total cBRS independent of stimulation condition during nerve stimulation (females: 14.96 ± 5.67 ms/mmHg, males: 11.89 ± 3.24 ms/mmHg, = 0.031) and rhythmic breathing at 0.2 Hz (females: 21.49 ± 8.47 ms/mmHg, males: 15.12 ± 5.70 ms/mmHg, = 0.004). Whereas vagus nerve stimulation at the left inner tragus did not affect the efferent vagal control of the heart, we found similar patterns of baroreceptor sensitivity activation over the stimulation period in both sexes, which, however, significantly differed in their magnitude, with females showing an overall higher cBRS.
Topics: Cross-Over Studies; Electric Stimulation; Female; Forearm; Heart Rate; Humans; Male; Pressoreceptors; Vagus Nerve; Vagus Nerve Stimulation
PubMed: 34769711
DOI: 10.3390/ijerph182111193 -
Bioelectromagnetics Oct 2022Mounting evidence suggests enhanced blood pressure (BP) variability (BPV) independent role in cardiovascular (CV) damage. The goal was to estimate the effect of the...
Mounting evidence suggests enhanced blood pressure (BP) variability (BPV) independent role in cardiovascular (CV) damage. The goal was to estimate the effect of the carotid baroreceptor (CB) magnetic stimulation on sudden high BP elevation. Mean femoral arterial BP (MAP), heart rate (HR), baroreflex sensitivity (BRS), and ear lobe skin microcirculatory blood flow, by microphotoelectric plethysmography (MPPG), were simultaneously recorded in conscious rabbits sedated by pentobarbital intravenous (i.v.) infusion (5 mg/kg/h) after 40 min CB exposure to 350 mT static magnetic field (SMF), by Nd -Fe -B magnets (n = 14), or sham magnets exposure (n = 14). BRS was assessed from HR and MAP responses to abrupt hypotension induced by i.v. bolus injections of nitroprusside (Ni) and abrupt MAP elevation (MAP ) by i.v. bolus of phenylephrine (Ph). Beat-to-beat BPV was estimated by MAP standard deviation. SMF CB exposure significantly increased BRS (74.5 ± 17.8%, P < 0.001) and microcirculation (23.8% ± 11.0%, P = 0.039); decreased MAP (-5.7 ± 1.7%, P < 0.014) and phenylephrine-induced MAP (-19.1%, P = 0.043). MAP positively correlated with resting MAP (r = 0.342, P = 0.0383) and MAP SD (r = 0.383, P = 0.0194), and inversely with BRS (r = -0.47, P = 0.0156). SMF CB exposure enhanced the nitroprusside, which acts by releasing nitric oxide (NO), vasodilatory effect. This indicates arterial baroreflex to improve vessel sensitivity to NO, which is a new physiology with BP buffering effect. A positive correlation of MAP SD to phenylephrine BP ramps suggests a causal relationship and BPV prognostic significance to forecast abrupt BP elevation. Mechano/baroreceptor magneto-sensing property proposed to be the basic physiology by which SMFs boost CV autonomic regulation with potential implementation in high CV risk labile arterial hypertensive disease. © 2022 Bioelectromagnetics Society.
Topics: Animals; Rabbits; Pressoreceptors; Blood Pressure; Microcirculation; Nitroprusside; Hypertension; Phenylephrine; Magnetic Fields
PubMed: 36403257
DOI: 10.1002/bem.22425 -
Acta Pharmacologica Sinica Dec 2021Female-specific subpopulation of myelinated Ah-type baroreceptor neurons (BRNs) in nodose ganglia is the neuroanatomical base of sexual-dimorphic autonomic control of...
Female-specific subpopulation of myelinated Ah-type baroreceptor neurons (BRNs) in nodose ganglia is the neuroanatomical base of sexual-dimorphic autonomic control of blood pressure regulation, and KCa1.1 is a key player in modulating the neuroexcitation in nodose ganglia. In this study we investigated the exact mechanisms underlying KCa1.1-mediated neuroexcitation of myelinated Ah-type BRNs in the presence or absence of estrogen. BRNs were isolated from adult ovary intact (OVI) or ovariectomized (OVX) female rats, and identified electrophysiologically and fluorescently. Action potential (AP) and potassium currents were recorded using whole-cell recording. Consistently, myelinated Ah-type BRNs displayed a characteristic discharge pattern and significantly reduced excitability after OVX with narrowed AP duration and faster repolarization largely due to an upregulated iberiotoxin (IbTX)-sensitive component; the changes in AP waveform and repetitive discharge of Ah-types from OVX female rats were reversed by G1 (a selective agonist for estrogen membrane receptor GPR30, 100 nM) and/or IbTX (100 nM). In addition, the effect of G1 on repetitive discharge could be completely blocked by G15 (a selective antagonist for estrogen membrane receptor GPR30, 3 μM). These data suggest that estrogen deficiency by removing ovaries upregulates KCa1.1 channel protein in Ah-type BRNs, and subsequently increases AP repolarization and blunts neuroexcitation through estrogen membrane receptor signaling. Intriguingly, this upregulated KCa1.1 predicted electrophysiologically was confirmed by increased mean fluorescent intensity that was abolished by estrogen treatment. These electrophysiological findings combined with immunostaining and pharmacological manipulations reveal the crucial role of KCa1.1 in modulation of neuroexcitation especially in female-specific subpopulation of myelinated Ah-type BRNs and extend our current understanding of sexual dimorphism of neurocontrol of BP regulation.
Topics: Animals; Estrogens; Female; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; Neurons; Nodose Ganglion; Ovariectomy; Ovary; Pressoreceptors; Quinolines; Rats, Sprague-Dawley; Rats
PubMed: 34267344
DOI: 10.1038/s41401-021-00722-4 -
Acta Pharmacologica Sinica Sep 2022Recent studies suggest that melatonin (Mel) plays an important role in the regulation of blood pressure (BP) via the aortic baroreflex pathway. In this study, we...
Recent studies suggest that melatonin (Mel) plays an important role in the regulation of blood pressure (BP) via the aortic baroreflex pathway. In this study, we investigated the interaction between the baroreflex afferent pathway and Mel-mediated BP regulation in rats under physiological and hypertensive conditions. Mel (0.1, 0.3, and 1.0 mg/mL) was microinjected into the nodose ganglia (NG) of rats. We showed that Mel-induced reduction of mean arterial pressure in female rats was significantly greater than that in male and in ovariectomized rats under physiological condition. Consistently, the expression of Mel receptors (MTNRs) in the NG of female rats was significantly higher than that of males. In L-NAME-induced hypertensive and spontaneously hypertensive rat models, MTNRs were upregulated in males but downregulated in female models. Interestingly, Mel-induced BP reduction was found in male hypertensive models. In whole-cell recording from identified baroreceptor neurons (BRNs) in female rats, we found that Mel (0.1 μM) significantly increased the excitability of a female-specific subpopulation of Ah-type BRNs by increasing the Na1.9 current density via a PKC-mediated pathway. Similar results were observed in baroreceptive neurons of the nucleus tractus solitarius, showing the facilitation of spontaneous and evoked excitatory post-synaptic currents in Ah-type neurons. Collectively, this study reveals the estrogen-dependent effect of Mel/MTNRs under physiological and hypertensive conditions is mainly mediated by Ah-type BRNs, which may provide new theoretical basis and strategies for the gender-specific anti-hypertensive treatment in clinical practice.
Topics: Animals; Baroreflex; Blood Pressure; Estrogens; Female; Hypertension; Male; Melatonin; Pressoreceptors; Rats; Rats, Inbred SHR; Rats, Sprague-Dawley
PubMed: 35132193
DOI: 10.1038/s41401-022-00867-w -
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 -
The Journal of Physiological Sciences :... Jun 2023This study investigated effects of experimental baroreceptor stimulation on bilateral blood flow velocities in the anterior and middle cerebral arteries (ACA and MCA)...
This study investigated effects of experimental baroreceptor stimulation on bilateral blood flow velocities in the anterior and middle cerebral arteries (ACA and MCA) using functional transcranial Doppler sonography. Carotid baroreceptors were stimulated by neck suction in 33 healthy participants. Therefore, negative pressure (- 50 mmHg) was applied; neck pressure (+ 10 mmHg) was used as a control condition. Heart rate (HR) and blood pressure (BP) were also continuously recorded. Neck suction led to reductions in bilateral ACA and MCA blood flow velocities, which accompanied the expected HR and BP decreases; HR and BP decreases correlated positively with the ACA flow velocity decline. The observations suggest reduction of blood flow in the perfusion territories of the ACA and MCA during baroreceptor stimulation. Baroreceptor-related HR and BP decreases may contribute to the cerebral blood flow decline. The findings underline the interaction between peripheral and cerebral hemodynamic regulation in autoregulatory control of cerebral perfusion.
Topics: Humans; Blood Flow Velocity; Pressoreceptors; Middle Cerebral Artery; Blood Pressure; Heart Rate
PubMed: 37312034
DOI: 10.1186/s12576-023-00871-7