Increased Vagal Activity Research Articles

Dopamine in the nucleus accumbens shell controls systemic glucose metabolism via the lateral hypothalamus and hepatic vagal innervation in rodents

BackgroundGrowing evidence demonstrates the role of the striatal dopamine system in the regulation of glucose metabolism. Treatment with dopamine antagonists is associated with insulin resistance and hyperglycemia, while dopamine agonists are used in treatment of type 2 diabetes. The mechanism underlying striatal dopamine effects in glucose metabolism, however is not fully understood. Here, we provide mechanistic insights into the role of nucleus accumbens shell (sNAc) dopaminergic signaling in systemic glucose metabolism. MethodsEndogenous glucose production (EGP), blood glucose and mRNA expression in the lateral hypothalamic area (LHA) in male Wistar rats were measured following infusion of vanoxerine (VNX, dopamine reuptake inhibitor) in the sNAc. Thereafter, we analyzed projections from sNAc Drd1-expressing neurons to LHA using D1-Cre male Long-Evans rats, Cre-dependent viral tracers and fluorescence immunohistochemistry. Brain slice electrophysiology in adult mice was used to study spontaneous excitatory postsynaptic currents of sNAc Drd1-expressing neurons following VNX application. Finally, we assessed whether GABAergic LHA activity and hepatic vagal innervation were required for the effect of sNAc-VNX on glucose metabolism by combining infusion of sNAc-VNX with LHA-bicuculline, performing vagal recordings and combining infusion of sNAc-VNX with hepatic vagal denervation. ResultsVNX infusion in the sNAc strongly decreased endogenous glucose production, prevented glucose increases over time, reduced Slc17A6 and Hcrt mRNA in LHA, and increased vagal activity. Furthermore, sNAc Drd1-expressing neurons increased spontaneous firing following VNX application, and viral tracing of sNAc Drd1-expressing neurons revealed direct projections to LHA with on average 67 % of orexin cells directly targeted by sNAc Drd1-expressing neurons. Importantly, the sNAc-VNX-induced effect on glucose metabolism was dependent on GABAergic signaling in the LHA and on intact hepatic vagal innervation. ConclusionsWe show that sNAc dopaminergic signaling modulates hepatic glucose metabolism through GABAergic inputs to glutamatergic LHA cells and hepatic vagal innervation. This demonstrates that striatal control of glucose metabolism involves a dopaminergic sNAc-LHA-liver axis and provides a potential explanation for the effects of dopamine agonists and antagonists on glucose metabolism.

Characteristics of deceleration capacity and deceleration runs in vasovagal syncope.

Increased vagal activity plays a prominent role in vasovagal syncope (VVS). The aim of this study was to characterize vagal function in VVS by evaluating the heart rate (HR) deceleration capacity (DC) and the HR deceleration runs (DRs) in patients with VVS between attacks. A total of 188 consecutive VVS patients were enrolled in the study, of whom 129 had positive head-up tilt test (HUTT); 132 healthy participants were enrolled as controls. DC, DRs (DR2, i.e., episodes of 2 consecutive beat-to-beat HR decelerations), and the sum of DR8-10 (very long DR [VLDR]) were calculated using 24-h electrograms. Clinical characteristics, DC, and DRs were compared among syncope groups and controls. Patients with VVS had higher DC (10.63 ± 2.1 vs. 6.58 ± 1.7ms; P < 0.001) and lower minimum HR and DR6-10 than controls. No significant differences in DC or DR6-10 were found between the patients with positive and those with negative HUTT results. In multivariate logistic regression analysis, minimum HR ≥ 40bpm (odds ratio [OR] 0.408, 95% confidence interval [CI] 0.167-0.989; P = 0.048), daytime DC ≥ 7.37ms (OR 3.040, 95% CI 1.220-7.576; P = 0.013), and VLDR ≥ 0.046% (OR 0.306, 95% CI 0.138-0.679; P = 0.004) were demonstrated to be risk factors significantly associated with VVS. Compared to healthy controls, patients with VVS demonstrated distinct HR deceleration profiles between attacks, including overall higher DC and lower DR6-10.

Exponential modelling of heart rate recovery after a maximal exercise

Objectives: Heart rate recovery (HRR) after exercise is clinically important as a predictor of mortality. In addition, HRR is an indicator of cardiac autonomic activity, since increased vagal activity and diminished sympathetic activity return the heart rate to resting conditions after exercise. The previous attempts to model HRR using polynomial, first-order and second-order modelling have produced mixed results. In this study, we hypothesised that the double-exponential fit would model the HRR more accurately than the single-exponential fit as it would capture the activity of both autonomic arms responsible for heart rate decay and investigated the outcome of these two models on the HRR data following a maximal exercise. Materials and Methods: Exponential curve fitting was done on a set of previously published data from our laboratory. The HRR data were acquired from 40 male participants (19–38 years) after a maximal treadmill exercise. The normalised HRR data from a 5-min time window from maximal heart rate were fitted using single and double-exponential curves, to obtain, respectively, the time constants Tau and, Tau 1 and Tau 2. The goodness-of-fit of the model was assessed with Chi-square values computed for each participant data set with both models. Considering that Chi-square of zero is a perfect fit, and therefore, smaller Chi-square values indicate a better fit than larger values, we computed the difference in the Chi-square values (Δχ2) between the models by subtracting the Chi-square value of the double-exponential fit from the Chi-square value of the single-exponential fit. This was based on the premise that if the calculated Δχ2 is positive, it would indicate a better fit with double-exponential than single-exponential decay model. The data are presented as mean ± standard deviation. Comparisons were made with Student’s t-test. Results: Data from four participants were excluded for technical reasons. The Tau of the single-exponential fit was 65.50 ± 12.13 s, while Tau 1 and Tau 2 of the double-exponential fit were 43.75 ± 18.96 s and 120.30 ± 91.32 s, respectively, the Tau 1 value being significantly lower than the Tau 2 value (P &lt; 0.0001). Remarkably among the 36 participants, the difference in the Chi-square value was positive (127.2 ± 171.04) in 22 subjects and zero or marginally negative (−0.17 ± 0.31) in 14 subjects. Conclusion: Our results indicate that the double-exponential model fitted the HRR data better than the single-exponential model in almost two-thirds (61%) of our study population. In the remaining participants, the goodness-of-fit was nearly equivalent for both fits with no evidence of superior modelling with the single-exponential fit. Our data show that while the single-exponential fit is sufficient for modelling the HRR of 14 subjects, it was less efficient for fitting the data of most participants. In comparison, the double-exponential curve fit effectively modelled 100% of our study population. Given our findings, we conclude that the double-exponential model is more inclusive and better represented the HRR data of our study population than the single-exponential model.

Induced Relaxation Enhances the Cardiorespiratory Dynamics in COVID-19 Survivors.

Most COVID-19 survivors report experiencing at least one persistent symptom after recovery, including sympathovagal imbalance. Relaxation techniques based on slow-paced breathing have proven to be beneficial for cardiovascular and respiratory dynamics in healthy subjects and patients with various diseases. Therefore, the present study aimed to explore the cardiorespiratory dynamics by linear and nonlinear analysis of photoplethysmographic and respiratory time series on COVID-19 survivors under a psychophysiological assessment that includes slow-paced breathing. We analyzed photoplethysmographic and respiratory signals of 49 COVID-19 survivors to assess breathing rate variability (BRV), pulse rate variability (PRV), and pulse-respiration quotient (PRQ) during a psychophysiological assessment. Additionally, a comorbidity-based analysis was conducted to evaluate group changes. Our results indicate that all BRV indices significantly differed when performing slow-paced breathing. Nonlinear parameters of PRV were more appropriate for identifying changes in breathing patterns than linear indices. Furthermore, the mean and standard deviation of PRQ exhibited a significant increase while sample and fuzzy entropies decreased during diaphragmatic breathing. Thus, our findings suggest that slow-paced breathing may improve the cardiorespiratory dynamics of COVID-19 survivors in the short term by enhancing cardiorespiratory coupling via increased vagal activity.

PO-01-126 SEXUAL DIMORPHISM AND CARDIAC ARRHYTHMIAS IN A MOUSE MODEL OF FRIEDREICH'S ATAXIA: WHAT DO WE KNOW?

Friedreich ataxia (FA) is a monogenic recessive disorder caused by the reduction of the mitochondrial protein, frataxin (FXN). Despite neurological deficits place patients with FA in the wheelchairs, most patients die from lethal cardiomyopathy in their 40s. FA patients develop progressive cardiac disease with characteristics similar to primary hypertrophic cardiomyopathy but with more progressive cardiac fibrosis, both diastolic and systolic dysfunction, and arrhythmias. However, the mechanisms leading to cardiomyopathy and arrhythmias in FA patients are poorly understood. To characterize electrical signal propagation and cardiac function in a mouse model which imitates the late-stage cardiomyopathy in FA patients. Cardiac-specific McK-Cre FXN knockout (FXN cKO) mice were used as a model of severe cardiomyopathy which is characteristic for the late-stage of FA. Due to premature death, animals of either sex at 8-weeks of age were used to assess cardiac function in-vivo by echocardiography and surface electrocardiogram (ECG). We found that FXN cKO mice developed idiosyncratic arrhythmias with varying time durations for beat-to-beat (RR) intervals and heart rate variability (HRV) parameters such as root mean squared successive differences (RMSSD, p<0.0358), revealing increased vagal activity. Mice presented extended P-wave (p<0.0113) and QTc intervals (>150 ms, p<0.0015), suggesting impaired atrial and left-ventricular function, resembling human patients. HRV frequency parameters showed increased low-frequency (0.023), high-frequency (p<0.264) and total (p<0.0326) power. Non-linear parameters showed varying short-term variation (SD1, p<0.019), increased long-term variation (SD2, p<0.0017) and ellipse area values (S, p<0.0074). Poincare plots of FXN cKO males included multiple clustering of RR and RR+1 identities while females generally sustained a single clustered ellipse (area, p<0.028). Similarly, QTc intervals were increased mostly in FXN cKO males. Contractile dysfunction was also more severe in FXN cKO males as evident by reduction in left ventricular fractional shortening, ejection fraction, stroke volume and cardiac output. Our study revealed sexual dimorphism and significant impairment in electrical and contractile function in FXN cKO males compared to females. A detailed characterization of impaired electrical signals in FA hearts will build a platform for drug testing to treat lethal cardiomyopathy in FA.

Massage stimulation’s effect on melatonin levels in preterm infants via vagal activity

Massage stimulation has been suggested to be used to promote the growth and development of preterm and low birth weight (LBW) infants. Some experts believe that infant massage can help develop the central nervous system, which increases vagal activity, improves hormone secretion, triggers the release of melatonin, and increases its production. Rhythmic endogenous melatonin secretion appears in term infants around 2-3 months of age, whereas preterm infants have delayed melatonin secretion, which persists after correction for 8 to 9 months of gestation. Massage stimulation increases vagal activity, which causes an increase in melatonin. Vagal activity then modulates pineal and extrapineal activity, resulting in melatonin production. Based on scientific evidence, current reviews suggest that massage stimulation can provide health benefits to newborns, particularly preterm infants. This article aims to review that massage stimulation can increase melatonin levels by activating vagal mechanisms.

Automatic Detection and Characterization of Autonomic Dysreflexia Using Multi-Modal Non-Invasive Sensing and Neural Networks.

Autonomic dysreflexia (AD) frequently occurs in persons with spinal cord injuries (SCIs) above the T6 level triggered by different stimuli below the level of injury. If improperly managed, AD can have severe clinical consequences, even possibly leading to death. Existing techniques for AD detection are time-consuming, obtrusive, lack automated detection capabilities, and have low temporal resolution. Therefore, a non-invasive, multi-modal wearable diagnostic tool was developed to quantitatively characterize and distinguish unique signatures of AD. Electrocardiography and novel skin nerve activity (skNA) sensors with neural networks were used to detect temporal changes in the sympathetic and vagal systems in rats with SCI. Clinically established metrics of AD were used to verify the onset of AD. Five physiological features reflecting different metrics of sympathetic and vagal activity were used to characterize signatures of AD. An increase in sympathetic activity, followed by a lagged increase in vagal activity during the onset of AD, was observed after inducing AD. This unique signature response was used to train a neural network to detect the onset of AD with an accuracy of 93.4%. The model also had a 79% accuracy in distinguishing between sympathetic hyperactivity reactions attributable to different sympathetic stressors above and below the level of injury. These neural networks have not been used in previous work to detect the onset of AD. The system could serve as a complementary non-invasive tool to the clinically accepted gold standard, allowing an improved management of AD in persons with SCI.

Transcutaneous Electrical Acustimulation Improves Irritable Bowel Syndrome With Constipation by Accelerating Colon Transit and Reducing Rectal Sensation Using Autonomic Mechanisms.

Slow colon transit and visceral hypersensitivity are recognized as major pathophysiological mechanisms in irritable bowel syndrome with constipation (IBS-C). However, there is a lack of therapies targeting both abdominal pain and colonic motility. This study was designed to investigate the long-term effects and possible mechanisms of transcutaneous electrical acustimulation (TEA) in patients with IBS-C. Fifty-two patients with IBS-C were randomized into 2 groups: daily TEA for 4 weeks (n = 26) and daily sham-TEA for 4 weeks (n = 26). The number of complete spontaneous bowel movements per week (CSBMs/week, primary outcome), Irritable Bowel Syndrome Severity Scoring System, Patient Assessment of Constipation Quality of Life, visual analog scale (VAS) pain score, colonic transit time, and anorectal physiology were evaluated before treatment and at the end of the treatment. Colonic transit was assessed with radiopaque markers. Electrocardiograms were recorded for assessing autonomic functions. (i) TEA improved constipation and abdominal pain. After the treatment, the number of CSBMs/week during the last week in the TEA group was higher than that in the sham-TEA group (3.5 ± 1.6 vs 2.3 ± 0.6, P = 0.002). Similar effects were also noted in the visual analog scale pain score ( P = 0.002) and Irritable Bowel Syndrome Severity Scoring System score ( P = 0.025). In addition, there was a significant improvement in the quality of life of patients with constipation. The Patient Assessment of Constipation Quality of Life total score was significantly decreased in the TEA group ( P = 0.004). (ii) Compared with sham-TEA, TEA improved colon transit ( P = 0.002) and increased the threshold of rectal sensation (desire to defecate, P = 0.004; maximum tolerability, P &lt; 0.001). (iii) TEA increased vagal activity, compared with sham-TEA ( P &lt; 0.05); at the end of the treatment, the vagal activity was significantly correlated with colon transit and the CSBMs/week. TEA improves constipation and symptoms of IBS by accelerating colon transit and reducing rectal sensation, possibly mediated by using the autonomic mechanisms.

A Comprehensive Study of Yoga for Major Depressive Illness

Traditional antidepressant pharmacotherapies or psychotherapies have been related to low remission rates or poor treatment adherence. Even though there is extensive study on the issue, yoga might have been an alternate therapeutic approach. This randomized controlled study utilised confused outcome assessors to look at an 8-week hatha yoga meditation program as a monotherapy for mild to moderate suffering. This article examines recent research on the effects of yoga postures on mental concerns like stress and sadness, psychological disorders, immune system, cardiovascular, or immunological illnesses, and pregnancy. Yoga's physiological benefits, such as reduced heart rate and blood pressure, as well as its physical consequences, such as weight reduction and improved muscular strength, are also discussed. Finally, possible underlying processes are suggested, such as pressure receptor activation leading to increased vagal activity and lower cortisol. Cortisol decrease may lead to beneficial outcomes like improved immunological function and a reduced incidence of preterm.

Stress, the autonomic nervous system, and sudden death

The existence of an important relationship between stress, the autonomic nervous system, and sudden cardiac death (SCD) has been long recognized. In the present essay we review the large number of conditions, acting at individual or at population level, that have been causally associated to SCD and discuss the mechanistic and translational value of the studies exploring such associations. These conditions include external stressors (earthquakes, wars) and internal stressors (anger, fear, loss of a loved one) and emotions of even opposite sign. Most situations confirm the time-honored view that increases in sympathetic activity are proarrhythmic whereas increases in vagal activity are protective; however, we will also show and discuss a condition in which the culprit appears to be the excess of vagal activity. The physiologic rationale underlying the most typical situations is on one hand the profibrillatory effect of the increase in the heterogeneity of repolarization secondary to the release of norepinephrine, and on the other the combined effect of acetylcholine to lower heart rate and to antagonize the cardiac effects of norepinephrine at ventricular level. An interesting facet of this potentially lethal relationship is that the elements involved are by no means always exceptional, and they can actually represent part of our everyday life.

Randomized Pilot Trial Using External Yarrow Liver Compress Applications With Metastatic Cancer Patients Suffering From Fatigue: Evaluation of Sympathetic Modulation by Heart Rate Variability Analysis.

Background:Liver compresses are commonly applied in complementary medicine during cancer treatment and are believed to have an energizing effect. We conducted a pilot study to investigate the influence of external application of yarrow liver compresses on the autonomous nervous system by analyzing the heart rate variability (HRV) in metastatic cancer patients undergoing radiation therapy and suffering from cancer-related fatigue (CRF).Methods:A randomized pilot trial was undertaken with patients suffering from CRF receiving palliative radiation therapy for bone or brain metastasis over 2 weeks. CRF patients were randomized into an intervention group receiving yarrow liver compresses and a control group receiving no external application. HRV was analyzed at the beginning (T1) and end (T2) period of the study during daytime (d) and nighttime (n) in both groups and quantified using time-, frequency-, and nonlinear dynamics domains.Results:A total of 39 patients were randomized between September 2017 and August 2019 and a total of 20 patients (10 per group) were available for analysis. For both groups, significant differences in HRV analyses were found in the comparison over the timeline between the first and second measurement (T1d→T2d) during daytime. Specifically, the intervention group showed decreased HRV and complexity of heart rate regulation, indicating increased sympathetic activity at time T2d, whereas the control group showed increased HRV and complexity of heart rate regulation, indicating increased vagal activity at time T2d. Furthermore, the observed HRV analyses showed almost no significant differences between the 2 groups in a direct comparison at the beginning and the end of the study (exception: T2d).Conclusions:Yarrow liver compresses led to increased sympathetic activity during daytime in the intervention group, whereas in the control group, which did not receive any external application, increased parasympathetic activity was observed.

Atrial fibrillation secondary to ephedrine administration and responsive to lidocaine in a Shiloh shepherd dog

AbstractA 6‐year‐old, 43 kg, male Shiloh shepherd dog was anaesthetised for computed tomography to investigate the source of respiratory distress, lethargy and decreased appetite. Arterial hypotension during anaesthesia was treated with an infusion of phenylephrine and a bolus of ephedrine, 0.05 mg/kg intravenously (IV). Ephedrine resulted in increased blood pressure and reflexive bradycardia; atrial fibrillation developed immediately after. Approximately 10 minutes later, a bolus of lidocaine 2 mg/kg IV was administered, and normal sinus rhythm was restored within 1 minute. Lone atrial fibrillation may be triggered by agents or disease processes that increase vagal activity. While lidocaine has historically been used only to treat unstable ventricular dysrhythmias, it is effective for terminating this particular type of atrial fibrillation.

Correlation of Heart Rate Variability with Carotid Intima Media Thickness after 6 Month of Yoga Intervention in Prediabetics.

Introduction:Atherosclerotic carotid intimamedia thickness (CIMT) may be associated with alterations in the autonomic functions. The aim of this study was to investigate the effect of 6-month yoga intervention on heart rate variability (HRV) and CIMT in elderly subjects and the correlation between HRV and CIMT.Methodology:This was a randomized controlled study, in which a total of 250 subjects were enrolled. Randomization and allocation in yoga and control groups were performed using computer-generated random numbers. The CIMT was determined by B-mode ultrasonography, and cardiac autonomic function was determined through frequency domain parameter of HRV measures at baseline and after 6 months of yoga intervention.Results:Participants had a mean age of 45.4 ± 6.4 years, and a mean CIMT in control (0.70 ± 0.05) and study group (0.69 ± 0.073), and low frequency/high frequency (LF/HF) ratio in control (2.20 ± 1.05) and study group (0.57 ± 0.54). Yoga group had evidence of increased vagal activity in the frequency domain (HF and LF/HF ratio, P < 0.001) with respect to control group. Moreover, a study group showed lower intimamedia thickness (IMT) than control subjects (P < 0.01). In the whole population, LF/HF ratio positively and significantly correlated (r = 0.665, P < 0.01) to IMT.Conclusion:This study demonstrated that, after yoga intervention, LF/HF ratio is positively correlated with CIMT, a putative index of atherosclerosis, confirming cardiac autonomic neuropathy as a part of the pathophysiological pathway for atherosclerosis. It confirms that the regular yoga represents a valuable strategy to counter impairments of cardiac autonomic activity and artery structural changes.

Immediate changes in cardiac autonomic tone and stroke volume during microgravity simulation using head-down tilt

Objectives: Gravity plays an important role in the day-to-day functioning of the cardiovascular system (CVS) in the human body. The absence of gravity severely affects CVS functioning. Out of existing simulation models of microgravity, the 6° head-down tilt (HDT) is frequently used analog to replicate the physiological effects of microgravity on earth. Materials and Methods: The present study has been designed to determine the specificity of 6° HDT usage as a microgravity simulation. The heart rate variability (HRV), blood pressure (BP), cardiac output (CO), and stroke volume (SV) responses to 5 min exposures were investigated for 4°, 6°, and 8° HDT. It was hypothesized that the graded HDT around 6° will demonstrate reversal of autonomic parameters. The study was conducted on 28 male subjects aged 20–30 years. Results: The study reveals that there was a significant rise in diastolic and mean BP at 6° and 8° HDT as compared to baseline. It was also observed that the high-frequency power in HRV was increased at 6° HDT (P = 0.026), with a concomitant reduction in the low-frequency power (P = 0.03) of HRV. The CO was increased at 6° and 8° HDT as compared to baseline (P = 0.037 and 0.021, respectively). There were no significant changes observed in any of the recorded parameters at 4° HDT. The cardiopulmonary volume receptors might have sensed the blood volume change in HDT as in microgravity simulation the blood passively shifts to cephalad. To overcome the low blood volume problem, the heart tried to pump extra blood through increased CO. At 8° HDT, it was observed that the cardiac sympathetic activity and CO were increased, which is not observed during microgravity exposures. Conclusion: The study suggests that 6° head-down-tilt is the best tilt level for producing microgravity on earth to study immediate cardiovascular parameters as it is a balanced compromise of increased vagal activity and CO without activation of cardiac sympathetic activity. Therefore, our data provide physiological evidence in support of 6° HDT microgravity simulation for the study of immediate cardiovascular responses.

Optimized Tibial Nerve Stimulation Partially Reduces Visceral Hypersensitivity in Rats Mediated via Autonomic and Opioid Mechanisms

The aim of this study was to investigate the therapeutic effect and possible mechanisms of tibial nerve stimulation (TNS) on visceral hypersensitivity in rats. 1) The effects of TNS with five sets of parameters on visceral sensitivity in normal rats were evaluated by the assessment of abdominal electromyogram (EMG) and abdominal withdrawal reflex (AWR). 2) The effects and mechanisms of TNS with a special set of parameters (14Hz, 330 μsec, and 40% motor threshold) were evaluated in acute visceral hypersensitivity rats induced by restraint stress and colonic hypersensitized rats induced by acetic acid during the neonatal stage assessed by the EMG, AWR, and the spectral analysis of heart rate variability derived from the electrocardiogram. 1) In normal rats, TNS did not show any effect on the visceromotor reflex. 2) In rats with restraint stress-induced hypersensitivity, TNS with the special set of parameters reduced AWR scores and EMG responses to rectal distention at a pressure of 20-60 mmHg (p < 0.05, vs. baseline for both AWR and EMG). Concurrently, TNS increased vagal activity and decreased sympathetic activity (p < 0.03 for both). 3) Similar effects were noted on the EMG (p < 0.05, vs. baseline) and AWR (p < 0.05 vs. baseline) with acute and chronic TNS in rats with chronic colonic hypersensitivity and the effects were blocked by naloxone. TNS with parameters of 14Hz, 330 μsec, and 40% motor threshold is effective in improving visceral hypersensitivity in rodent models of colonic hypersensitivity via the modulation of autonomic and opioid mechanisms.

Greater muscle strength is associated with reduced autonomic reactivity

We aimed to investigate the autonomic responses to cold pressor test (CPT) in individual with different levels of muscle strength. 57 male subjects participated in the study. Volunteers were divided in tertiles according to their level of relative handgrip strength as Low (LS), Medium (MS) and High (HS). For the CPT the volunteers remained seated in resting for 15 minutes and inserted the right hand in cold water for two minutes. Blood pressure (BP) measurements were taken at rest, during CPT and during recovery. HRV was continuously recorded during the entire protocol. All three groups had similar BP variation, with the values of systolic blood pressure (SBP) increasing during CPT and diminishing during recovery until the third minute. At the first CPT minute LS group showed a substantial increase in low-frequency (LF) activity and a diminished high frequency (HF). LS also presented higher and lower values of LF and HF, respectively, than MS group at the first CPT minute. HS showed an increased vagal activity during recovery. In conclusion, individuals from LS presented similar BP responses to CPT than MS and HS groups but with higher sympathetic activation. HS individuals presented an elevated vagal activity during recovery.

Evidence that Young Normotensive South Asians Show Early Signs of Disturbed Arterial Blood Pressure (ABP) Regulation of in Acute Mental Stress Relative to White Europeans

The risk of cardiovascular disease (CVD) including hypertension is higher in South Asians (SAs) than White Europeans (WEs). But, whether disturbances in autonomic control of the cardiovascular system are present in early adulthood in SAs has not been tested. Thus, we performed studies on young 20 WEs and 21 SAs aged (21.9±0.36, 20.7±0.41 respectively, equal numbers of men and women in each group) in whom arterial blood pressure (ABP), electrocardiogram (ECG), heart rate (HR) and respiration were recorded at rest, during mental stress (3 min Colour Stroop test) and during 5 min slow breathing (6 breaths/min). Stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were computed from the pulse contour. Baroreflex sensitivity (BRS) was calculated by the sequence method as change in R-R interval evoked by spontaneous up and down sequences in systolic pressure (SP) at rest and during mental stress and as the relationship between R-R interval and the fall in SP evoked by standing from a squat before and at 0, 3, 6 min following the stress test. HRV was computed in time-domain during mental stress and slow breathing. Comparisons within and between WEs and SAs were done by paired and un-paired t-tests respectively. At rest, WEs and SAs had similar mean ABP (mABP, 86.9±1.42 vs 87.1±1.77mmHg), HR (71.1±2.45 vs 76.2±3.56 beats/min), CO (4.8±0.21 vs 5.2±0.21L/min), SV (76.5±3.86 vs 81.5±2.97ml), TPR (1.14±0.06 vs 1.01±0.04 resistance units), and BRS (up-sequence: 1.2±0.05, down-sequence: 1.2±0.05 vs 1.0±0.09 and 1.2±0.09ms/mmHg). Further, mental stress evoked similar increases in mABP and HR in WEs and SAs but was accompanied by an increase CO in WEs and by an increase in TPR in SAs. Concomitantly, vagal indices of HRV were depressed during mental stress in SAs only (RMSSD: 66.2±7.8 to56.2±11.4 and 67.6±8.7 to 50.0±6.5*ms, *: P<0.05 within WE or SAs). Further during up-sequences in SP, BRS was depressed in both SAs and WEs during mental stress, but during down-sequences, BRS was depressed in WE only (to 0.59±0.10 vs 0.96±0.08*ms/mmHg). Also, following mental stress, BRS during squat to stand, an index of vagosympathetic activity, was depressed in WEs only (0.5±0.04 at rest to 0.3±0.04* vs 0.5±0.06 to 0.5±0.06ms/mmHg). On the other hand, slow breathing, tended to decrease ABP in both WEs and SAs (82.1±1.8 to 79.2±2.1mmHg: P<0.05; 79.4±2.0 to 77.4±2.0mmHg: P=0.09 respectively) and increased vagal indices of HRV in both WEs and SAs (66.3±8.6 to 86.0±13.2*ms; 67.6±8.7 to 86.48.8*ms). These results suggest that during and after mental stress, young normotensive SAs show greater sympathetic vasoconstriction than WEs, and attenuated respiratory modulation of HR, while their ability to evoke baroreflex tachycardia by vagal inhibition and sympathetic activation is preserved relative to young WEs. Such disturbances in would be expected to increase the risk of future CVD and hypertension in SAs, particularly in those with high levels of daily stress. The finding that slow breathing increased vagal activity in young SAs raises the possibility that regular slow breathing may help to normalize autonomic regulation of ABP in SAs and limit future CVD.

Tone it down: Vagal nerve activity is associated with pro-inflammatory and anti-viral factors in breast cancer – An exploratory study

In response to adverse social-environmental conditions, leukocytes gene expression profile is altered in a pattern recognized as the conserved transcriptional response to adversity (CTRA). This entails the up-regulated expression of pro-inflammatory genes and down-regulated expression of genes involved in type-I interferon (IFN) related anti-viral immunity. In contrast, vagal nerve activity is recognized as a significant anti-inflammatory modulator. In this work, we investigated the association between CTRA and vagal activity indicated by the standard deviation of all NN interval (SDNN), a measure of heart-rate variability, in breast cancer patients awaiting surgery (n = 16). This association was tested both at the molecular leukocyte transcription factor activity level, as well as at the cytokines serum levels. We found an association between higher SDNN and increased interferon (IFN) related anti-viral pathways, both on the leukocyte transcription factor level and serum protein level. Unexpectedly, we also found a positive correlation between higher SDNN and pro-inflammatory transcription factor activity and cytokine serum level, potentially suggesting that increased vagal activity was induced by increased inflammation, in the context of pre-surgical stress and the presence of malignant tissue. Transcription origin analysis (TOA) suggests a role for monocyte and B-cells in the anti-inflammatory and anti-metastatic effects induced by vagal nerve signaling. Larger prospective studies are needed to verify and elaborate on the results from this small cross-sectional study.

The effects of six-week slow, controlled breathing exercises on heart rate variability in physically active, healthy individuals

Background and Study Aim: Heart rate variability (HRV) provides information about sympathetic-parasympathetic balance. The effects of different types of physical exercises on HRV have been investigated so far. The purpose of the current study was to evaluate the chronic effects of six-week slow and controlled breathing exercise on HRV in physically active, healthy adults.&#x0D; Material and Methods: A total of 22 individuals (11 female, 11 male) participated in the study voluntarily. The experimental group (EG) attended to the breathing exercises for 15 minutes per day, three days a week for six weeks. Neither the EG nor the control group (CG) did join in any regular physical activity program during the study. Both groups participated in the HRV measurements before and after the six-week of process.&#x0D; Results: Only the EG showed statistically significant changes in some HRV parameters. The alterations observed in LF:HF ratio, HFnu, and LFnu parameters were to reflect the increase in parasympathetic activity. Although the changes in the other parameters of HRV such as SDNN, SDSD, RMSSD, TP, HF, LF, and VLF were also related to increased vagal activity, these alterations were not significant. However, no significant change was found in the CG.&#x0D; Conclusions: These results show that only the slow, controlled breathing exercises for six weeks could be used to improve parasympathetic activity in physically active individuals. A study could be designed where the duration is kept over 8 weeks, and the effects of physical exercises only, breathing exercises only, and physical + breathing exercises together on HRV are examined.

The effects of six-week slow, controlled breathing exercises on heart rate variability in physically active, healthy individuals

Background and Study Aim: Heart rate variability (HRV) provides information about sympathetic-parasympathetic balance. The effects of different types of physical exercises on HRV have been investigated so far. The purpose of the current study was to evaluate the chronic effects of six-week slow and controlled breathing exercise on HRV in physically active, healthy adults.&#x0D; Material and Methods: A total of 22 individuals (11 female, 11 male) participated in the study voluntarily. The experimental group (EG) attended to the breathing exercises for 15 minutes per day, three days a week for six weeks. Neither the EG nor the control group (CG) did join in any regular physical activity program during the study. Both groups participated in the HRV measurements before and after the six-week of process.&#x0D; Results: Only the EG showed statistically significant changes in some HRV parameters. The alterations observed in LF:HF ratio, HFnu, and LFnu parameters were to reflect the increase in parasympathetic activity. Although the changes in the other parameters of HRV such as SDNN, SDSD, RMSSD, TP, HF, LF, and VLF were also related to increased vagal activity, these alterations were not significant. However, no significant change was found in the CG.&#x0D; Conclusions: These results show that only the slow, controlled breathing exercises for six weeks could be used to improve parasympathetic activity in physically active individuals. A study could be designed where the duration is kept over 8 weeks, and the effects of physical exercises only, breathing exercises only, and physical + breathing exercises together on HRV are examined.