Electroacupuncture decreases the susceptibility to ventricular tachycardia in conscious rats by reducing cardiac metabolic demand

Median nerve stimulation elevates ventricular fibrillation threshold via the cholinergic anti-inflammatory pathway in myocardial infarction canine model

Background

Median nerve stimulation (MNS) diminishes regional myocardial ischemia and ventricular arrhythmia; however, the underlying mechanism has not been elucidated.

Methods

In this study, we randomly categorized 22 adult mongrel dogs into a control group, MNS group 1, and MNS group 2. After a 4-week experimental myocardial infarction (MI), ventricular electrophysiology was measured in the MNS group 1 before and after 30 min of MNS. The same measurements were performed in the MNS group 2 dogs via bilateral vagotomy. Venous blood and ventricular tissue were collected to detect molecular indicators related to inflammation and cholinergic pathways by enzyme-linked immunosorbent assay (ELISA), immunohistochemistry (IHC), and Western blot (WB).

Results

No significant changes were reported in the ventricular effective refractory period (ERP) in the MNS group 1 and MNS group 2 dogs before and after MNS. The ventricular fibrillation threshold (VFT) in the MNS group 1 was significantly higher than that in the MNS group 2 (20.3 ± 3.7 V vs. 8.7 ± 2.9 V, P < 0.01). The levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and nuclear transcription factor-κB (NF-κB) were lower (P < 0.01), whereas the levels of Ach were higher in the peri-infarct zone tissues in the MNS group 1 dogs than those in the MNS group 2 dogs (P < 0.01).

Conclusion

This study demonstrated that MNS increases VFT in a canine model with MI. The effects of MNS on VFT are potentially associated with the cholinergic anti-inflammatory pathway.

Effects of post-treatment electroacupuncture on ventricular monophasic action potential and cardiac function in a rat model of ischemia/reperfusion injury

BACKGROUND

To determine the effects of post-treatment electroacupuncture (EA) on the electrophysiological properties of ventricular muscle in rats with ischemia/reperfusion (IR) injury.

METHODS

Male Sprague-Dawley (SD) rats were randomly assigned into sham-operated (SH), IR and IR + EA groups (n = 8 each). The IR model was generated by ligation of the left anterior descending (LAD) coronary artery for 30 min. After establishing the IR model, EA was administered at PC6 for 30 min while opening the coronary artery and allowing reperfusion for 30 min. Heart rate (HR), mean arterial pressure and monophasic action potential (MAP) of cardiac muscle in the outer membrane of the antetheca of the left ventricle before coronary artery ligation (T₀), after coronary artery ligation for 30 min (T₁) and after reperfusion for 30 min (T₂) were recorded. At the same time, ventricular electrophysiological parameters including ventricular effective refractory period (ERP), conduction velocity (CV) and ventricular fibrillation threshold (VFT) were measured. Then, the cardiac function and the levels of creatine kinase-muscle/brain (CK-MB) and cardiac troponin I (cTnI) were monitored. Based on these data, monophasic action potential amplitude (MAPA), the maximum depolarization velocity (V_max) and the MAP durations at 50% and 90% repolarization (MAPD₅₀ and MAPD₉₀) were calculated to determine the incidence of arrhythmia during reperfusion.

RESULTS

Compared with the SH group, the IR group showed an obviously decreased HR as well as reduced mean arterial pressure, V_max, CV, ERP and MAPA. All indices of cardiac function except left ventricular end-diastolic pressure (LVEDP) decreased (i.e. ventricular systolic pressure (LVSP), left ventricular ejection fraction (LVEF), fractional shortening (FS) and rate of the ventricular pressure rise/drop (±dp/dt)). Furthermore, the MAPD₅₀ and MAPD₉₀ were prolonged, and the levels of CK-MB and cTnI increased (p < 0.05). In comparison to the IR group, HR and the mean arterial pressure were increased. All indices of cardiac function except LVEDP increased (LVSP, LVEF, FS and ±dp/dt). V_max, CV, ERP and MAPA were also increased in the IR + EA group. However, MAPD₅₀ and MAPD₉₀ were distinctly shortened, and the levels of CK-MB and cTnI decreased (p < 0.05). There were no statistically significant differences in VFT between the three groups (p > 0.05).

CONCLUSION

EA post-treatment can relieve prolongation of repolarization and slowed depolarization of ventricular muscle during IR, thus decreasing the rate of incidence of reperfusion arrhythmia.

Electroacupuncture Pretreatment Mitigates Myocardial Ischemia/Reperfusion Injury via XBP1/GRP78/Akt Pathway

Myocardial ischemia/reperfusion injury is a common clinical problem and can result in severe cardiac dysfunction. Previous studies have demonstrated the protection of electroacupuncture against myocardial ischemia/reperfusion injury. However, the role of X-box binding protein I (XBP1) signaling pathway in the protection of electroacupuncture was still elusive. Thus, we designed this study and demonstrated that electroacupuncture significantly improved cardiac function during myocardial ischemia/reperfusion injury and reduced cardiac infarct size. Electroacupuncture treatment further inhibited cardiac injury manifested by the decrease of the activities of serum lactate dehydrogenase and creatine kinase-MB. The results also revealed that electroacupuncture elevated the expressions of XBP1, glucose-regulated protein 78 (GRP78), Akt, and Bcl-2 and decreased the Bax and cleaved Caspase 3 expressions. By using the inhibitor of XBP1 in vitro, the results revealed that suppression of XBP1 expression could markedly increase the activities of lactate dehydrogenase and creatine kinase-MB and cell apoptosis, thus exacerbating stimulated ischemia/reperfusion-induced H9c2 cell injury. Compared with stimulated ischemia/reperfusion group, inhibition of XBP1 inhibited the downstream GRP78 and Akt expressions during stimulated ischemia/reperfusion injury. Collectively, our data demonstrated that electroacupuncture treatment activated XBP1/GRP78/Akt signaling to protect hearts from myocardial ischemia/reperfusion injury. These findings revealed the underlying mechanisms of electroacupuncture protection against myocardial ischemia/reperfusion injury and may provide novel therapeutic targets for the clinical treatment of myocardial ischemia/reperfusion injury.

Electroacupuncture improves cardiac function and reduces infarct size by modulating cardiac autonomic remodeling in a mouse model of myocardial ischemia

BACKGROUND

Sympathetic and parasympathetic nerve remodeling play an important role in cardiac function after myocardial ischemia (MI) injury. Increasing evidence indicates that electroacupuncture (EA) can regulate cardiac function by modulating the autonomic nervous system (ANS), but little is known about its effectiveness on neural remodeling post-MI.

OBJECTIVES

To investigate the role of EA in ANS remodeling post-MI.

METHODS

Adult male C57/BL6 mice were equally divided into the Control (Ctrl), MI and EA groups after generating the MI model by ligating the left anterior descending (LAD) coronary artery. Echocardiography and 2,3,5-triphenyltetrazolium (TTC) staining were employed to evaluate cardiac function and infarct size after EA treatment for five consecutive days. Serum norepinephrine (NE) levels were measured by ELISA to quantify sympathetic activation. Then, ANS remodeling was detected by immunohistochemistry (IHC), RT-qPCR, and Western blotting.

RESULTS

Our preliminary findings showed that EA increased ejection fraction and fractional shortening and reduced infarct area after MI injury. Serum NE levels in the EA group were significantly decreased compared with those in the MI group. IHC staining results demonstrated that the density of growth associated protein (GAP)43 and tyrosine hydroxylase (TH) positive nerve fibers in the EA group were decreased with increased choline acetyltransferase (CHAT) and vesicular acetylcholine transporter (VACHT). Meanwhile, the results verified that mRNA and protein expression of GAP43 and TH were significantly inhibited by EA treatment in the MI mice, accompanied by elevated CHAT and VACHT.

CONCLUSIONS

EA treatment could improve cardiac function and reduce infarct size by modulating sympathetic and parasympathetic nerve remodeling post-MI, thus helping the cardiac ANS reach a new balance to try to protect the heart from further possible injury.

Electroacupuncture preconditioning attenuates acute myocardial ischemia injury through inhibiting NLRP3 inflammasome activation in mice

AIMS

Electro-acupuncture pretreatment (EAP) plays a protective role in myocardial ischemia (MI) injury. However, the underlying mechanism remains unclear. A growing body of evidence suggests postinfarction inflammatory response directly affects the remodeling of ventricular function. The purpose of this study was to investigate whether EAP alleviates MI through NLRP3 inflammasome inhibition.

MATERIALS AND METHODS

We constructed an AMI model by ligating the left anterior descending (LAD) coronary artery after 3 days of EAP with C57BL/6 mice. Echocardiography and TTC staining were employed to evaluate cardiac function and infarct size after 24 h of ischemia. HE staining and immunohistochemistry were employed to determine inflammatory level. Then, inflammasome activation was detected by western blotting, and macrophage polarization and neutrophil infiltration were observed by flow cytometry.

KEY FINDINGS

Our preliminary findings showed that EAP reduced the infarct area and increased fractional shortening (FS) and ejection fraction (EF) and decreased the degree of inflammation after AMI injury. Meanwhile, EAP inhibited the expression of NLRP3, cleaved caspase-1 and IL-1β in ischemia myocardial tissue, companied by inhibiting the expression of F4/80⁺, CD11b⁺, CD206^low macrophages and activated M2 macrophage, and decreasing Ly-6G⁺CD11b⁺ neutrophils in ischemia myocardial and spleen tissue.

SIGNIFICANCE

EAP inhibits the activation of NLRP3 inflammasome, promotes M2 polarization of macrophages and reduces the recruitment of neutrophils in damaged myocardium, thereby decreases the infarct size and improves the cardiac function.

Electroacupuncture enhances antioxidative signal pathway and attenuates neuropathic pain induced by chemotherapeutic paclitaxel

One of the significant limiting complications of paclitaxel is painful peripheral neuropathy during its therapy for several types of cancers. Our recent study showed that impairment of Nrf2-antioxidant response element (Nrf2-ARE) and upregulation of oxidative signals in the dorsal root ganglion (DRG) of rats with treatment of paclitaxel result in neuropathic pain. The purpose of this study was to examine the beneficial role played by electroacupuncture (EA) in modifying neuropathic pain evoked by paclitaxel via Nrf2-ARE and oxidative mechanisms. Behavioral test was performed to determine mechanical and thermal sensitivity in rats. Western Blot analysis and ELISA were used to examine expression of Nrf2-ARE and superoxide dismutases (SOD); and the levels of products of oxidative stress in the DRG. Our data showed that paclitaxel increased mechanical and thermal sensitivity and this was accompanied with impaired Nrf2-ARE and SOD in the DRG and amplified products of oxidative stress (i.e. 8-isoprostaglandin F2alpha and 8-hydroxy-2'-deoxyguanosine). EA treatment largely restored the levels of Nrf2-ARE/SOD and inhibited products of oxidative stress and thereby attenuated mechanical and thermal hypersensitivity induced by paclitaxel. In conclusion, we revealed specific signaling pathways leading to paclitaxel-evoked neuropathic pain, including impairment of Nrf2-ARE and heightened oxidative signals. We further provided evidence for the role of EA in alleviating paclitaxel-neuropathic pain via these molecular mediators.

Median nerve stimulation prevents atrial electrical remodelling and inflammation in a canine model with rapid atrial pacing

Aims

Studies have shown that stellate ganglion nerve activity has association with atrial electrical remodelling and atrial fibrillation (AF) inducibility, while median nerve stimulation (MNS) decreases cardiac sympathetic drive. In this study, we tested the hypothesis that MNS suppresses atrial electrical remodelling and AF vulnerability.

Methods and results

The atrial effective refractory period (AERP) and AF inducibility at baseline and after 3 h of rapid atrial pacing were determined in dogs undergoing MNS (n = 7), MNS+ application of methyllycaconitine (n = 7) or sham procedure (n = 6). Then, the levels of tumour necrosis factor-alpha (TNF-a), interleukin-6 (IL-6), and acetylcholine (Ach) in the plasma and atrial tissues were measured. The control dogs (n = 4) were assigned to measure atrial inflammation cytokines. Short-term rapid atrial pacing induced shortening of the AERP, an increase in AERP dispersion, and an increase AF vulnerability in the sham dogs, which were all suppressed by MNS. Levels of TNF-a and IL-6 were higher, and Ach levels were lower in the left and the right atrium in the sham dogs than in the MNS dogs. Methyllycaconitine blunted the effects of MNS on the AERP, AERP dispersion, the AF vulnerability, and TNF-a and IL-6 levels in the atrium, but had no impact on the levels of Ach.

Conclusions

The effects of MNS on atrial electrical remodelling and AF inducibility might be associated with the cholinergic anti-inflammatory pathway.

Attenuation of hypertension by C-fiber stimulation of the human median nerve and the concept-based novel device

High blood pressure (BP) is a highly controllable risk factor for cardiovascular diseases; however, awareness of this condition and the rates of controlled hypertension are low. Experimental animal studies have shown that stimulation of the median nerve or PC6 acupoint over the wrist has effects on cardiovascular activities, including reductions in systolic and diastolic BPs. A proof-of-concept study was conducted in humans to investigate whether stimulation of median nerve near PC6 acupoint decreased high BP, identify the optimal stimulation parameters for the BP-lowering effects of median nerve stimulation, and determine the specific peripheral nerves or types of afferent fibers mediating the BP-lowering effects. Median nerve stimulation was carried out bilaterally or unilaterally with different stimulation parameters, and the BP and heart rate were monitored. The afferent mechanisms underlying the effects of median nerve stimulation on hypertension were investigated via microneurography, A-fiber blocking experiments, and localized chemical or electrical stimulation. Bilateral median nerve stimulation at either low or high frequencies produced profound but transient reductions in systolic BP, which were elicited when median nerve stimulation was unilaterally applied at interelectrode distances of 2 and 4 cm. Systolic BP was also reduced by electrical stimulation of the thumb on the palm side. Although microneurographic recordings revealed the excitation of both A- and C-fibers following median nerve stimulation, the median nerve-mediated reductions in BP were not affected by A-fiber blockade, and they were mimicked by the activation of C-fibers with capsaicin. The present results indicate that activation of C-fibers in the median nerve generates BP-lowering effects in humans. Based on our clinical study, an optimized median nerve stimulator was built and combined with a wrist BP monitor for simultaneous BP measurements and median nerve stimulation.

Chronic median nerve modulation reduces ventricular arrhythmia and improves ventricular function in a postmyocardial infarction rabbit model

AIM

Median nerve stimulation (MNS) is a novel neuromodulation approach for treatment of ventricular arrhythmia, but little is known about its chronic effects. The aim of this study was to investigate the effects of chronic MNS on ventricular arrhythmia and ventricular dysfunction postmyocardial infarction (MI).

METHOD

Two weeks after MI, 12 rabbits were randomly divided into control and MNS groups, and chronic MNS was performed in MNS group for 2 weeks. Ventricular function and arrhythmias; sympathetic innervation and activity; and interleukin-1 β (IL-1 β) and norepinephrine (NE) levels were analyzed.

RESULTS

Both the total number of premature ventricular complex and episodes of ventricular tachycardia were lower in MNS group than in control group (20 560 ± 10 314 beats vs 70 079 ± 37 184 beats, P = .021, and 115 ± 63 episodes vs 307 ± 164 episodes, P = .034, respectively). Compared with control group, MNS decreased the cardiac sympathetic nerve density and level of circulating NE in MNS group (1798.42 ± 644.07 μm² /mm² vs 1003.79 ± 453.00 μm² /mm²_, P = .041, and 20.86 ± 4.54 pg/mL vs 11.07 ± 1.43 pg/mL, P = .002, respectively). MNS also improved the left ventricular ejection fraction (59.07 ± 1.91% vs 49.77 ± 3.47%, P = .003) and inhibited the level of IL-1 β in serum (69.19 ± 4.71 pg/mL vs 85.93 ± 12.80 pg/mL, P = .013).

CONCLUSION

Chronic MNS appears to protect against ventricular arrhythmia and improves ventricular function post-MI, which may be mediated by suppressing cardiac sympathetic activity and anti-inflammatory effects.

Median nerve stimulation reduces ventricular arrhythmias induced by dorsomedial hypothalamic stimulation

BACKGROUND

This study tested the hypothesis that median nerve stimulation (MNS) prevents ventricular arrhythmias (VAs) induced by dorsomedial hypothalamus stimulation (DMHS) and investigated the electrophysiological mechanisms underlying the anti-arrhythmic effects of MNS by recording left stellate ganglion activity (LSGA).

METHODS

Eighteen rabbits were anesthetized, the median nerve was anchored by stimulating electrodes, and a bipolar electrode was implanted into the LSG to record nerve activity. The DMH was stimulated to induce arrhythmia. All animals underwent six repetitions of DMHS (30 s). The 18 rabbits were divided into the following 3 groups: a control group, which underwent only DMHS (n = 6); an MNS group, which underwent MNS during both the third and fourth DMHS repetitions (n = 6); and an LSGA-recording group, for which LSGA was recorded at baseline, immediately following DMHS and again immediately following MNS and DMHS (n = 6).

RESULTS

Repeated DMHS-induced multiple VAs, in the rabbits. Compared with the DMHS-only group, the concurrent administration of MNS during DMHS significantly reduced the incidence of VAs (7 ± 3 and 9 ± 2 beats for the third and fourth DMHS + MNS repetitions vs. 29 ± 8 and 27 ± 9 beats for the first two DMHS repetitions, p < 0.05). The total duration of the abnormal discharges of the LSG (ADLSG) following MNS and DMHS was significantly reduced compared with that of the DMHS-only group (40 ± 18 vs. 14 ± 6 s, p < 0.05).

CONCLUSION

MNS reduced VAs induced by DMHS, which is thought to be mediated through suppressing of ADLSG.

NEW AND NOTEWORTHY

Median nerve electrical stimulation prevented ventricular arrhythmias induced by DMHS through the mechanism of suppressing abnormal discharges of left stellate ganglion.

Cardioprotective Effect of Electroacupuncture Pretreatment on Myocardial Ischemia/Reperfusion Injury via Antiapoptotic Signaling

Objectives. Our previous study has used RNA-seq technology to show that apoptotic molecules were involved in the myocardial protection of electroacupuncture pretreatment (EAP) on the ischemia/reperfusion (I/R) animal model. Therefore, this study was designed to investigate how EAP protects myocardium against myocardial I/R injury through antiapoptotic mechanism. Methods. By using rats with myocardial I/R, we ligated the left anterior descending artery (LAD) for 30 minutes followed by 4 hr of reperfusion after EAP at the Neiguan (PC6) acupoint for 12 days; we employed arrhythmia scores, serum myocardial enzymes, and cardiac troponin T (cTnT) to evaluate the cardioprotective effect. Heart tissues were harvested for western blot analyses for the expressions of pro- and antiapoptotic signaling molecules. Results. Our preliminary findings showed that EAP increased the survival of the animals along with declined arrhythmia scores and decreased CK, LDH, CK-Mb, and cTnT levels. Further analyses with the heart tissues detected reduced myocardial fiber damage, decreased number of apoptotic cells and the protein expressions of Cyt c and cleaved caspase 3, and the elevated level of Endo G and AIF after EAP intervention. At the same time, the protein expressions of antiapoptotic molecules, including Xiap, BclxL, and Bcl2, were obviously increased. Conclusions. The present study suggested that EAP protected the myocardium from I/R injury at least partially through the activation of endogenous antiapoptotic signaling.

Vagal modulation of high mobility group box-1 protein mediates electroacupuncture-induced cardioprotection in ischemia-reperfusion injury

Excessive release of high mobility group box-1 (HMGB1) protein from ischemic cardiomyocytes activates inflammatory cascades and enhances myocardial injury after reperfusion. Here we report evidence that electroacupuncture of mice at Neiguan acupoints can inhibit the up-regulation of cardiac HMGB1 following myocardial ischemia and attenuate the associated inflammatory responses and myocardial injury during reperfusion. These benefits of electroacupuncture were partially reversed by administering recombinant HMGB1 to the mice, and further potentiated by administering anti-HMGB1 antibody. Electroacupuncture-induced inhibition of HMGB1 release was markedly reduced by unilateral vagotomy or administration of nicotinic receptor antagonist, but not by chemical sympathectomy. The cholinesterase inhibitor neostigmine mimicked the effects of electroacupuncture on HMGB1 release and myocardial ischemia reperfusion injury. Culture experiments with isolated neonatal cardiomyocytes showed that acetylcholine, but not noradrenaline, inhibited hypoxia-induced release of HMGB1 via a α7nAchR-dependent pathway. These results suggest that electroacupuncture acts via the vagal nerve and its nicotinic receptor-mediated signaling to inhibit HMGB1 release from ischemic cardiomyocytes. This helps attenuate pro-inflammatory responses and myocardial injury during reperfusion.

Protein and RNA expression of acid-sensing ion channels 2 and 3 in myocardial ischemia rats induced by isoproterenol

OBJECTIVE

To investigate the impact of electro-acupuncture at the Neiguan (PC 6) acupoint on protein and RNA expression of acid-sensing ion channel 2 (ASIC2) and ASIC3 in myocardial ischemia rats.

METHODS

Fifty male Sprague-Dawley rats were used, weighing (230 ± 50) g. The rats were randomized into a normal group A, model group B, Neiguan (PC 6) group C, Lieque (LU 7) group D, and A-shi points group E. There were 10 rats in each group. Rats were continuously administered 85 mg/ kg intravenous isoproterenol daily to establish the model. Successfully modeled rats in groups C, D, and E were given electro-acupuncture treatment. Each group of rats was sacrificed with chloral hydrate (1 mL/100 g) intraperitoneal injection. The left ventricular myocardium was extracted and placed at -70 °C until use. Western blot analysis and real-time PCR were performed to assay protein and RNA expressions of ASIC2 and ASIC3, respectively. Fold changes in RNA expression were quantified with the 2^ (-ΔΔCt) method. Blood samples were drawn from the aorta abdominalis and tested for creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) levels using enzyme-linked immunosorbent assay.

RESULTS

Myocardial ischemia rats given electro-acupuncture at the Neiguan (PC 6) acupoint had significantly lower protein and RNA expression of ASIC2 and ASIC3, and CK-MB and LDH levels, compared with model rats (P < 0.01).

CONCLUSION

Electro-acupuncture at the Neiguan (PC 6) acupoint can not only decrease the protein and RNA expression of ASIC2 and ASIC3, but also inhibit the opening of ASICs and reduce the cardiomyocyte damage in myocardial ischemia rats.

Acupuncture antiarrhythmic effects on drug refractory persistent atrial fibrillation: study protocol for a randomized, controlled trial

Background. Atrial fibrillation (AF) is the most common form of arrhythmia. Several trials have suggested that acupuncture may prevent AF. However, the efficacy of acupuncture for AF prevention has not been well investigated. Therefore, we designed a prospective, two-parallel-armed, participant and assessor blinded, randomized, sham-controlled clinical trial to investigate acupuncture in persistent AF (ACU-AF). Methods. A total of 80 participants will be randomly assigned to active acupuncture or sham acupuncture groups in a 1 : 1 ratio. Both groups will take the same antiarrhythmic medication during the study period. Patients will receive 10 sessions of acupuncture treatment once a week for 10 weeks. The primary endpoint is AF recurrence rate. Secondary endpoints are left atrium (LA) and left atrial appendage (LAA) changes in function and volume, and inflammatory biomarker changes. Ethics. This study protocol was approved by the institutional review boards (IRBs) of Kyung Hee University Hospital (number 1335-04). This trial is registered with clinicaltrials.gov NCT02110537.

Anti-arrhythmic effect of acupuncture pretreatment in the rats subjected to simulative global ischemia and reperfusion--involvement of intracellular Ca2+ and connexin 43

BACKGROUND

The previous study showed that the cardiac arrhythmias induced by myocardial ischemia and reperfusion were attenuated by the pretreatment of acupuncture; however, the related mechanism is not understood. The present study was therefore designed to determine whether intracellular Ca(2+) ([Ca(2+)]i) and connexin 43 (Cx43) are involved in the mediation of the anti-arrhythmic effect of electro-acupuncture (EA) pretreatment in the rats subjected to simulative global ischemia and reperfusion (SGIR).

METHODS

SGIR was made in the isolated heart by a low flow perfusion followed by a flow restoration. Four groups of animals are involved in the present study, including normal control group, SGIR group, EA group and EA plus 18 beta-glycyrrhetinic acid (EAG) group. For EA pretreatment, bilateral Neiguan acupoints (PC6) of the rats were stimulated for 30 min once a day in 3 consecutive days. Cx43 antagonist was given to the rats in EAG group 30 minutes before the EA pretreatment. The resting [Ca(2+)]i concentration, calcium oscillation, the contents of total Cx43 and non-phosphrylated Cx43 and arrhythmia score were compared among different groups.

RESULTS

In EA group, the arrhythmic score, the resting [Ca(2+)]i concentration and the number of [Ca(2+)]i oscillations were all significantly less than those in SGIR group (all P < 0.05), and interestingly, after EA pretreatment, the contents of nonphosphated Cx43 in the EA group were significantly lower than that in SGIR group respectively (P < 0.05). However, when the rats were treated with Cx43 antagonist prior to the EA pretreatment, the protection effects induced by EA pretreatment were reversed.

CONCLUSIONS

The results showed that EA pretreatment could produce anti-arrhythmic effect in the rats subjected to SGIR. The anti-arrhythmic effect of EA pretreatment may be due at least partially to the inhibition of SGIR-induced calcium overload and [Ca(2+)]i oscillations, reduction of non-phosphorylated Cx43 and the enhancement of the corresponding phosphorylated Cx43 in the cardiac cells.

Electroacupuncture of neiguan (PC 6) inhibits enhanced voltage-gated sodium currents in ischemic ventricular myocytes

OBJECTIVE

To examine the effect of electroacupuncture (EA) at bilateral Neiguan (PC 6) on voltage-gated Na+ currents (I(Na)) and channels (Na(v)) in ischemic ventricular myocytes.

METHODS

EA serum was prepared from six male adult Sprague-Dawley rats that had received EA at bilateral Neiguan (PC 6). Eighteen ventricular myocytes were prepared from six SD rats using an enzymolysis approach. Myocardial ischemia was mimicked by perfusion of ischemic solution. Whole-cell patch-clamping was used to record three currents evoked from isolated cells. The first current was the control, and recorded in absence of ischemic solution current. The second was the ischemic current, and recorded after perfusion of ischemic solution for 5 min, while the EA current was last, and recorded after perfusion of EA serum for 5 min. Na(v) kinetic curves were fitted using related formulas.

RESULTS

Compared with those in controls, in the presence of ischemic solution, peak amplitudes of I(Na) significantly increased from - 40 mV to +30 mV, and half-maximal inactivation potentials of Na(v) increased significantly, while half-maximal activation potentials, slope factors and the recovery time from inactivation to activation of Na(v) were unchanged. Compared with those in the ischemic solution, in the presence of EA serum, peak ischemic current amplitudes significantly reduced from - 40 mV to +40 mV, and half-maximal inactivation potentials were restored, while half-maximal activation potentials, slope factors and the recovery time from inactivation to activation of Na(v) were unchanged.

CONCLUSION

EA at bilateral Neiguan (PC 6) can reduce enhanced I(Na) via restoration of delayed Na(v) inactivation in ischemic ventricular myocytes.

Electroacupuncture improves cardiac function and remodeling by inhibition of sympathoexcitation in chronic heart failure rats

Chronic heart failure (CHF) is responsible for significant morbidity and mortality worldwide, mainly as a result of neurohumoral activation. Acupuncture has been used to treat a wide range of diseases and conditions. In this study, we investigated the effects of electroacupuncture (EA) on the sympathetic nerve activity, heart function, and remodeling in CHF rats after ligation of the left anterior descending coronary artery. CHF rats were randomly selected to EA and control groups for acute and chronic experiments. In the acute experiment, both the renal sympathetic nerve activity and cardiac sympathetic afferent reflex elicited by epicardial application of capsaicin were recorded. In the chronic experiment, we performed EA for 30 min once a day for 1 wk to test the long-term EA effects on heart function, remodeling, as well as infarct size in CHF rats. The results show EA significantly decreased the renal sympathetic nerve activity effectively, inhibited cardiac sympathetic afferent reflex, and lowered the blood pressure of CHF rats. Treating CHF rats with EA for 1 wk dramatically increased left ventricular ejection fraction and left ventricular fraction shortening, reversed the enlargement of left ventricular end-systolic dimension and left ventricular end-diastolic dimension, and shrunk the infarct size. In this experiment, we demonstrated EA attenuates sympathetic overactivity. Additionally, long-term EA improves cardiac function and remodeling and reduces infarct size in CHF rats. EA is a novel and potentially useful therapy for treating CHF.

ERK1/2-Egr-1 Signaling Pathway-Mediated Protective Effects of Electroacupuncture in a Mouse Model of Myocardial Ischemia-Reperfusion

Early growth response- (Egr-) 1 is an upstream master switch in controlling inflammatory responses following myocardial ischemia-reperfusion (I/R). Activation of extracellular signal-regulated protein kinase-1 and kinase-2 (ERK1/2) signaling is known to upregulate Egr-1. ERK1/2 pathway has been previously shown to mediate the therapeutic action of electroacupucture (EA). Thus, we hypothesized that EA would reduce myocardial I/R injury and inflammatory responses through inhibiting Egr-1 expression via the ERK1/2 pathway. Mice were pretreated with EA, U0126, or combination of EA and U0126 and then underwent 1 h myocardial ischemia and 3 h reperfusion. We investigated that EA significantly attenuated the I/R-induced upregulation of both Egr-1 and phosporylated-ERK1/2 (p-ERK1/2), decreased myocardial inflammatory cytokines including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and reduced the infarct size and the release of cardiac troponin I (cTnI). U0126 treatment also exhibited the same effect as EA on Egr-1 level and subsequent cardioprotective effects. There was no additive effect of cotreatment with EA and U0126 on the expression of Egr-1 and its downstream target genes (TNF-α, IL-1β) or serum cTnI level. Collectively, these observations suggested that EA attenuates myocardial I/R injury, possibly through inhibiting the ERK1/2-Egr-1 signaling pathway and reducing the release of proinflammatory cytokines.

Acupuncture promotes angiogenesis after myocardial ischemia through H3K9 acetylation regulation at VEGF gene

Background

Acupuncture exerts cardioprotective effects on several types of cardiac injuries, especially myocardial ischemia (MI), but the mechanisms have not yet been well elucidated. Angiogenesis mediated by VEGF gene expression and its modification through histone acetylation has been considered a target in treating myocardial ischemia. This study aims to exam whether modulation of angiogenesis through H3K9 acetylation regulation at VEGF gene is one possible cardioprotective mechanism of acupuncture.

Results

We generated rat MI models by ligating the left anterior descending coronary artery and applied electroacupuncture (EA) treatment at the Neiguan (PC6) acupoint. Our results showed that acupuncture reversed the S-T segment change, reduced Q-wave area, decreased CK, CK-MB, LDH levels, mitigated myocardial remodeling, and promoted microvessel formation in the MI heart. RNA-seq analysis showed that VEGF-induced angiogenesis signaling was involved in the modulation of EA. Western blot results verified that the protein expressions of VEGF, Ras, phospho-p44/42 MAPK, phospho-p38 MAPK, phospho-SAPK/JNK and Akt, were all elevated significantly by EA treatment in the MI heart. Furthermore, increased H3K9 acetylation was also observed according with the VEGF. ChIP assay confirmed that EA treatment could notably stimulate the recruitment of H3K9ace at the VEGF promoter.

Conclusions

Our study demonstrates for the first time that acupuncture can effectively up-regulate VEGF expression through H3K9 acetylation modification directly at the VEGF promoter and hence activate VEGF-induced angiogenesis in rat MI models. We employed high throughput sequencing in this study and, for the first time, generated genome-wide gene expression profiles both in the rat MI model and in acupuncture treatment.

Absence of actions of commonly used Chinese herbal medicines and electroacupuncture on myocardial infarct size

BACKGROUND

Some studies have suggested that certain Chinese herbal remedies and acupuncture could limit ischemia/reperfusion damage. We sought to determine whether the commonly used single herb Danshen (DS), either alone or in combination with Jiang Xiang (JX), or electroacupuncture (EA) reduces myocardial infarct size.

METHODS

An anesthetized rat model of proximal left coronary artery occlusion (30 minutes) and reperfusion (180 minutes) was used to measure infarct size (triphenyltetrazolium chloride) and ischemic risk zone (blue dye technique). Rats were either untreated (saline) or received an infusion of DS or DS + JX, starting 30 minutes prior to coronary occlusion. In a separate protocol, rats were untreated, received static needle (ND) placement without stimulation or EA at P5-P6 acupuncture points in the rat forearm starting 5 minutes before occlusion and lasting for 40 minutes, or starting 30 minutes before occlusion and lasting for 90 minutes.

RESULTS

In the herbal experiments, myocardial infarct size expressed as a fraction of the ischemic risk zone was 0.43 ± 0.06 in controls, 0.39 ± 0.05 in the DS group, and 0.42 ± 0.04 in the Danshen + JX groups (P = not significant [NS]). In the acupuncture study, there was no significant difference in infarct size as a fraction of the risk zone among the control group (0.38 ± 0.04), the ND group (0.47 ± 0.04), or the EA group (0.32 ± 0.05). When EA was started 30 minutes prior to coronary occlusion and continued for 30 minutes into reperfusion, infarct size was 0.41 ± 0.07 in controls and 0.38 ± 0.10 in EA (P = NS). Neither herbs nor EA altered heart rate or blood pressure. In a separate study of 5 minutes of coronary occlusion plus reperfusion, EA failed to reduce ventricular arrhythmias.

CONCLUSION

Our studies do not suggest a cardioprotective effect of DS or DS + JX or EA in an experimental model of myocardial ischemia/reperfusion.

Myocardial ischemia, reperfusion, and infarction in chronically instrumented, intact, conscious, and unrestrained mice

In the United States alone, the National Heart, Lung, and Blood Institute (NHLBI) has invested several hundred million dollars in pursuit of myocardial infarct-sparing therapies. However, due largely to methodological limitations, this investment has not produced any notable clinical application or cardioprotective therapy. Among the major methodological limitations is the reliance on animal models that do not mimic the clinical situation. In this context, the limited use of conscious animal models is of major concern. In fact, whenever possible, studies of cardiovascular physiology and pathophysiology should be conducted in conscious, complex models to avoid the complications associated with the use of anesthesia and surgical trauma. The mouse has significant advantages over other experimental models for the investigation of infarct-sparing therapies. The mouse is inexpensive, has a high throughput, and presents the ability of one to create genetically modified models. However, successful infarct-sparing therapies in anesthetized mice or isolated mouse hearts may not be successful in more complex models, including conscious mice. Accordingly, a conscious mouse model of myocardial ischemia and reperfusion has the potential to be of major importance for advancing the concepts and methods that drive the development of infarct-sparing therapies. Therefore, we describe, for the first time, the use of an intact, conscious, and unrestrained mouse model of myocardial ischemia-reperfusion and infarction. The conscious mouse model permits occlusion and reperfusion of the left anterior descending coronary artery in an intact, complex model free of the confounding influences of anesthetics and surgical trauma. This methodology may be adopted for advancing the concepts and ideas that drive cardiovascular research.

Cardioprotection of electroacupuncture against myocardial ischemia-reperfusion injury by modulation of cardiac norepinephrine release

Augmentation of cardiac sympathetic tone during myocardial ischemia has been shown to increase myocardial O(2) demand and infarct size as well as induce arrhythmias. We have previously demonstrated that electroacupuncture (EA) inhibits the visceral sympathoexcitatory cardiovascular reflex. The purpose of this study was to determine the effects of EA on left ventricular (LV) function, O(2) demand, infarct size, arrhythmogenesis, and in vivo cardiac norepinephrine (NE) release in a myocardial ischemia-reperfusion model. Anesthetized rabbits (n = 36) underwent 30 min of left anterior descending coronary artery occlusion followed by 90 min of reperfusion. We evaluated myocardial O(2) demand, infarct size, ventricular arrhythmias, and myocardial NE release using microdialysis under the following experimental conditions: 1) untreated, 2) EA at P5-6 acupoints, 3) sham acupuncture, 4) EA with pretreatment with naloxone (a nonselective opioid receptor antagonist), 5) EA with pretreatment with chelerythrine (a nonselective PKC inhibitor), and 6) EA with pretreatment with both naloxone and chelerythrine. Compared with the untreated and sham acupuncture groups, EA resulted in decreased O(2) demand, myocardial NE concentration, and infarct size. Furthermore, the degree of ST segment elevation and severity of LV dysfunction and ventricular arrhythmias were all significantly decreased (P < 0.05). The cardioprotective effects of EA were partially blocked by pretreatment with naloxone or chelerythrine alone and completely blocked by pretreatment with both naloxone and chelerythrine. These results suggest that the cardioprotective effects of EA against myocardial ischemia-reperfusion are mediated through inhibition of the cardiac sympathetic nervous system as well as opioid and PKC-dependent pathways.

Efeitos da eletroacupuntura, aquapuntura e farmacopuntura em cadelas anestesiadas com isofluorano e submetidas à ovário-histerectomia

Avaliaram-se os efeitos analgésicos da eletroacupuntura, aquapuntura e farmacopuntura com morfina nos acupontos VB41 e TA5 de 24 cadelas hígidas submetidas à ovário-histerectomia. Os animais foram distribuídos em quatro grupos (G) de igual número - GDest, GMorf, GElet e GC - e anestesiados com acepromazina, propofol e isofluorano. Após a estabilização do plano anestésico, os animais do GDest receberam 0,5mL de água destilada em cada acuponto; os do GMorf receberam 0,1mg/kg de morfina distribuído nos quatro acupontos; os do GElet foram submetidos à eletroacupuntura; e os do GC, acupuntura em pontos sham. Os animais do GC receberam, após o término do procedimento cirúrgico e antes do início da avaliação pelas escalas de dor, 2,0mg/kg de tramadol. Foram avaliadas: frequências cardíaca e respiratória, temperatura retal e glicemia. A dor foi avaliada por duas escalas, uma de analogia numérica e outra contagem variável, por três observadores. A avaliação iniciou-se imediatamente após a extubação e foi realizada a cada 15 minutos, durante duas horas. Não houve diferença entre os tratamentos em todas as variáveis. Pode-se concluir que eletroacupuntura, aquapuntura e farmacopuntura com morfina resultaram em analgesia similar ao tramadol no pós-operatório imediato de cadelas submetidas à ovário-histerectomia eletiva.

Cardiac spinal deafferentation reduces the susceptibility to sustained ventricular tachycardia in conscious rats

The response to myocardial ischemia is complex and involves the cardio-cardiac sympathetic reflex. Specifically, cardiac spinal (sympathetic) afferents are excited by ischemic metabolites and elicit an excitatory sympathetic reflex, which plays a major role in the genesis of ventricular arrhythmias. For example, brief myocardial ischemia leads to ATP release, which activates cardiac spinal afferents through stimulation of P2 receptors. Clinical work with patients and preclinical work with animals document that disruption of this reflex protects against ischemia-induced ventricular arrhythmias. However, the role of afferent signals in the initiation of sustained ventricular tachycardia has not been investigated. Therefore, we tested the hypothesis that cardiac spinal deafferentation reduces the susceptibility to sustained ventricular tachycardia in adult (12-15 wk of age), conscious, male Sprague-Dawley rats. To test this hypothesis, the susceptibility to ventricular tachyarrhythmias produced by occlusion of the left main coronary artery was determined in two groups of conscious rats: 1) deafferentation (bilateral excision of the T1-T5 dorsal root ganglia) and 2) control (sham deafferentation). The ventricular arrhythmia threshold (VAT) was defined as the time from coronary occlusion to sustained ventricular tachycardia resulting in a reduction in arterial pressure. Results document a significantly higher VAT in the deafferentation group (7.0 ± 0.7 min) relative to control (4.3 ± 0.3 min) rats. The decreased susceptibility to tachyarrhythmias with deafferentation was associated with a reduced cardiac metabolic demand (lower rate-pressure product and ST segment elevation) during ischemia.

Activation of reciprocal pathways between arcuate nucleus and ventrolateral periaqueductal gray during electroacupuncture: involvement of VGLUT3

Electroacupuncture (EA) at the Jianshi-Neiguan acupoints (P5-P6, overlying the median nerve) attenuates sympathoexcitatory responses through activation of the arcuate nucleus (ARC) and ventrolateral periaqueductal gray (vlPAG). Activation of the ARC or vlPAG respectively leads to neuronal excitation of the both nuclei during EA. However, direct projections between these two nuclei that could participate in central neural processing during EA have not been identified. The vesicular glutamate transporter 3 (VGLUT3) marks glutamatergic neurons. Thus, the present study evaluated direct neuronal projections between the ARC and vlPAG during EA, focusing on neurons containing VGLUT3. Seven to ten days after unilateral microinjection of a rodamine-conjugated microsphere retrograde tracer (100nl) into the vlPAG or ARC, rats were subjected to EA or served as a sham-operated control. Low frequency (2Hz) EA was performed bilaterally for 30min at the P5-P6 acupoints. Perikarya containing the microsphere tracer were found in the ARC and vlPAG of both groups. Compared to controls (needle placement without electrical stimulation), c-Fos immunoreactivity and neurons double-labeled with c-Fos, an immediate early gene and the tracer were increased significantly in the ARC and vlPAG of EA-treated rats (both P<0.01). Moreover, some neurons were triple-labeled with c-Fos, the retrograde tracer and VGLUT3 in the two nuclei following EA stimulation (P<0.01, both nuclei). These results suggest that direct reciprocal projections between the ARC and vlPAG are available to participate in prolonged modulation by EA of sympathetic activity and that VGLUT3-containing neurons are an important neuronal phenotype involved in this process.

Partial hindlimb occlusion reduced the susceptibility to sustained ventricular tachycardia in conscious rats

Remote conditioning induced by ischemia in distant organs protects the heart from ischemia/reperfusion injury; however, its effect on ischemia-induced ventricular arrhythmias is unknown. Therefore, we tested the hypothesis that partial hindlimb occlusion during coronary artery occlusion increases the ventricular arrhythmia threshold (VAT) induced by coronary artery occlusion. Rats (n = 7) were instrumented with a radio-telemetry device for recording arterial pressure, electrocardiogram (ECG), and body temperature. A Doppler ultrasonic flow probe and vascular occluder were placed around the terminal aorta. Finally, a snare was placed around the left main coronary artery. The VAT was determined without and, on an alternate day, during partial hindlimb occlusion (remote conditioning) in conscious rats. Without remote conditioning, the VAT was 4.56 + 0.15 minutes. Importantly, remote conditioning significantly increased the VAT (6.29 + 0.49 minutes), suggesting that ischemia in a distant organ may delay the development of ischemia-induced ventricular arrhythmias.

Effects of electroacupuncture on cardiac and gastric activities in acute myocardial ischemia rats

AIM: To observe the effect of electroacupuncture (EA) of “Neiguan” (PC6) and “Gongsun” (SP4) on pathological changes of the heart and stomach in rats with acute myocardial ischemia (AMI), and to explore its underlying mechanism.

METHODS: Fifty Wistar rats were randomized into control, model, PC6, SP4 and PC6 + SP4 groups (n = 8 each group). An AMI model was established by occlusion of the descending anterior branch (DAB) of the left coronary artery. ECG-ST of cervico-thoracic lead and electrogastrogram (EGG) were recorded. EA was applied to PC6, SP4 and PC6 + SP4 groups, respectively. At the end of experiments, the rats were transcardically perfused with 4% paraformaldehyde, and the heart base myocardium, gastric antrum and duodenum tissues were sampled, sectioned and stained with a reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase histochemical method for displaying nitric oxide synthase (NOS) activity.

RESULTS: After AMI, ECG-ST values elevated. After EA, the elevated ECG-ST values at 20 min in PC6 group, at 30 min in PC6 + SP4 and SP4 groups had no significant differences in comparison with their respective basal values before AMI. Following AMI, the amplitude and frequency of slow waves of EGG decreased remarkably (P < 0.05). At 30 min after EA, the mean amplitude and frequency of slow waves of EGG in the three EA groups had no marked differences compared with their individual basal levels and those in the control group. After AMI, the mean integral grey values of NOS-positive product in myocardium, gastric antrum and duodenum tissues in the model group increased remarkably in comparison with the control group, while those in three EA groups were lower than those in the model group. No significant differences were found in ECG-ST and EGG improvement among the three EA groups. However, EA of PC6 had a better effect on ECG-ST and EA of PC4 had a better effect on EGG, respectively.

CONCLUSION: EA of PC6, SP4 and PC6 + SP4 can significantly promote the recovery of cardiac and gastric electrical activities after AMI, and up-regulate NOS expression in myocardium, gastric antrum and duodenum tissues.

Possible Effects of Acupuncture on Atrial Fibrillation and Post-Herpetic Neuralgia – a Case Report

A 72 year old female with a main complaint of severe post-herpetic neuralgia and a secondary complaint of atrial fibrillation (AF) received two series of acupuncture treatments totalling 20 treatments over a four month period. Her standard medical treatment remained unchanged. The primary focus of the acupuncture was pain relief; however, two acupuncture points (PC6, SP4) were included in both treatment series because of possible effects on both costal or chest pain and cardiac arrhythmias, according to Traditional Chinese Medicine (TCM) teaching and limited research. As recorded by her pacemaker, estimated weekly episodes of AF in the patient decreased significantly, and percentage time in AF decreased with borderline statistical significance, from the pretreatment estimates during the second series of treatments (weekly AF episode estimates: pretreatment =71.4; second series =16.5, difference estimates =−54.9, 95% CI −6.5 to −103.3, P=0.02; percentage time in AF estimates: pretreatment =30.6; 2 second series =18.0, difference estimates = −12.6, 95% CI 0.9 to −26.0, P=0.08). The pain levels were also significantly reduced following the acupuncture treatment series by more than 67%. Further studies are warranted to further explore these observations of a possible effect of acupuncture on both atrial fibrillation and post-herpetic neuralgia.

Sex differences to myocardial ischemia and beta-adrenergic receptor blockade in conscious rats

We recently documented sex differences in the susceptibility to reperfusion-induced sustained ventricular tachycardia and beta-adrenergic receptor blockade in conscious rats. However, the effect of sex on ischemia-induced ventricular arrhythmias and beta-adrenergic receptor blockade is under-investigated. Therefore, we tested the hypothesis that gonadal hormones influence the ventricular arrhythmia threshold (VAT) induced by coronary artery occlusion as well as the response to beta-adrenergic receptor blockade. The VAT was defined as the time from coronary occlusion to sustained ventricular tachycardia resulting in a reduction in arterial pressure. Male and female intact and gonadectomized (GnX) rats were instrumented with a radiotelemetry device for recording arterial pressure, temperature, and ECG, as well as a Doppler ultrasonic flow probe to measure cardiac output and a snare around the left main coronary artery. The VAT was determined in conscious rats by pulling on the snare. The VAT was significantly longer in intact females (5.56 +/- 0.19) vs. intact males (4.31 +/- 0.14 min). This sex difference was abolished by GnX. Specifically, GnX decreased the VAT in females (4.55 +/- 0.22) and increased the VAT in males (5.14 +/- 0.30 min). Thus male sex hormones increase and female sex hormones decrease the susceptibility to ischemia-induced sustained ventricular tachycardia. beta-Adrenergic receptor blockade increased the VAT in intact males and GnX females only. Thus gonadal hormones influence the response to beta-adrenergic receptor blockade. Uncovering major differences between males and females in the pathophysiology of the cardiovascular system may result in sex-specific optimization of patient treatments.

T5 spinal cord transection increases susceptibility to reperfusion-induced ventricular tachycardia by enhancing sympathetic activity in conscious rats

We recently documented that paraplegia (T(5) spinal cord transection) alters cardiac electrophysiology and increases the susceptibility to ventricular tachyarrhythmias induced by programmed electrical stimulation. However, coronary artery occlusion is the leading cause of death in industrially developed countries and will be the major cause of death in the world by the year 2020. The majority of these deaths result from tachyarrhythmias that culminate in ventricular fibrillation. beta-Adrenergic receptor antagonists have been shown to reduce the incidence of sudden cardiac death. Therefore, we tested the hypothesis that chronic T(5) spinal cord transection increases the susceptibility to clinically relevant ischemia-reperfusion-induced sustained ventricular tachycardia due to enhanced sympathetic activity. Intact and chronic (4 wk after transection) T(5) spinal cord-transected (T(5)X) male rats were instrumented to record arterial pressure, body temperature, and ECG. In addition, a snare was placed around the left main coronary artery. The susceptibility to sustained ventricular tachycardia produced by 2.5 min of occlusion and reperfusion of the left main coronary artery was determined in conscious rats by pulling on the snare. Reperfusion culminated in sustained ventricular tachycardia in 100% of T(5)X rats (susceptible T(5)X, 10 of 10) and 0% of intact rats [susceptible intact, 0 of 10 (P < 0.05, T(5)X vs. intact)]. Beta-adrenergic receptor blockade prevented reperfusion-induced sustained ventricular tachycardia in T(5)X rats [susceptible T(5)X 0 of 8, 0% (P < 0.05)]. Thus paraplegia increases the susceptibility to reperfusion-induced sustained ventricular tachycardia due to enhanced sympathetic activity.