Sympathetic Nervous Regulation Research Articles

Device-Based Sympathetic Nerve Regulation for Cardiovascular Diseases.

Sympathetic overactivation plays an important role in promoting a variety of pathophysiological processes in cardiovascular diseases (CVDs), including ventricular remodeling, vascular endothelial injury and atherosclerotic plaque progression. Device-based sympathetic nerve (SN) regulation offers a new therapeutic option for some CVDs. Renal denervation (RDN) is the most well-documented method of device-based SN regulation in clinical studies, and several large-scale randomized controlled trials have confirmed its value in patients with resistant hypertension, and some studies have also found RDN to be effective in the control of heart failure and arrhythmias. Pulmonary artery denervation (PADN) has been clinically shown to be effective in controlling pulmonary hypertension. Hepatic artery denervation (HADN) and splenic artery denervation (SADN) are relatively novel approaches that hold promise for a role in cardiovascular metabolic and inflammatory-immune related diseases, and their first-in-man studies are ongoing. In addition, baroreflex activation, spinal cord stimulation and other device-based therapies also show favorable outcomes. This review summarizes the pathophysiological rationale and the latest clinical evidence for device-based therapies for some CVDs.

Spatiotemporal Control of ERK Activity by b2‐adrenergic Signaling

G‐protein coupled receptors (GPCRs) play vital roles in regulating physiological functions, such as sympathetic nervous regulation, and senses of vision and olfaction. Signaling of the β2‐adrenergic receptor (β2‐AR), which is a prototypical class A GPCR, has been proposed to control activation of ERK, subsequently regulating different processes including gene expression. However, the molecular mechanism of ERK activation downstream of β2AR signaling is not clearly understood. Here we investigate the molecular mechanism of β2‐AR mediated ERK activation using improved version of FRET‐based ERK biosensors targeted to various subcellular regions which enable us to visualize spatial and temporal regulation of ERK activity in living cells. Epinephrine stimulation leads to increases of ERK activity at the endosome and in the nucleus but not at the plasma membrane. An Nb37 nanobody that stables the active Gαsconformation enhances and prolongs the endosomal and nuclear ERK activity. We propose a new model that an endosome‐localized active β2AR recruits critical signaling components to facilitate ERK activation on the endosome. These findings provide a molecular basis for location selective activation of ERK by β2‐AR signaling.Support or Funding InformationThis work was supported by the National Institutes of Health (R01 DK073368 to J.Z.)

Multifractal Detrended Fluctuation Analysis of Congestive Heart Failure Disease Based on Constructed Heartbeat Sequence

Heart rate variability (HRV) can be used as a common detection method for congestive heart failure (CHF). Existing researches regarding HRV, including both linear indicators and nonlinear characteristics, are mostly based on the RR intervals of the ECG signal. This article proposed a sequence that can reflect the regulation of sympathetic and parasympathetic nerve on heart rate, and on this basis, conducted multifractal detrended fluctuation analysis (MFDFA). We extracted multifractal features to quantitatively compare the complexity of proposed sequence between the healthy and CHF groups. Results showed that abnormal physiological and pathological conditions due to the weakening of autonomic nerve control can reduce the complexity of the heartbeat signal. Estimate the separation performance of all features, the best discrimination is obtained for the area under the mass index spectrum S1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> as providing 100% accuracy in separating the Healthy Young and CHF groups, and 90.93% separation accuracy between the Healthy Elderly and CHF groups. This work provide a good basis for the diagnosis of CHF with a novel perspective.

P2565Decreased cardiac pacemaking and attenuated beta-adrenergic response in tric-a knock-out mice

Abstract Background Trimeric intracellular cation (TRIC) channels are expressed on the surface of the sarcoplasmic reticulum and compensate for calcium release from ryanodine receptors. Tric-a knock-out (KO) mice showed diminished calcium release from ryanodine receptors in vascular smooth muscle cells. The cardiac pacemaker is controlled by the surface membrane and intracellular calcium clocks. In spontaneously firing sinus node action potentials, the membrane and calcium clocks work together via numerous interactions modulated by membrane voltage, intracellular calcium release, and protein phosphorylation. Intracellular calcium changes modulate cardiac pacemaking in the sinus node, but the physiological importance of TRIC channels in cardiac rhythm formation is still obscure. Purpose In this study, we aimed to clarify the importance of TRIC channels on cardiac pacemaking using Tric-a KO mice. Methods The expression level of mRNA and proteins in the sinus node was examined by RT-PCR and immunoblotting. Systolic blood pressure was measured with tail-cuff method. Heart rate was measured by ECG, and heart rate variability was examined. The atrial contractile force from isolated hearts was measured with a force transducer. Cardiac action potential and spontaneous sinus rate from isolated hearts were measured with a microelectrode. Isoproterenol was used for sympathetic nerve manipulation. Results Tric-a KO heart showed increased adrenergic β1-receptor expression in immunoblotting. Although there was no significant difference in basal systolic blood pressure between Tric-a KO and wild type (WT) mice, basal heart rate in Tric-a KO mice was significantly lower than that in WT mice (660±10 and 698±10 bpm, n=15 and 19, Tric-a KO mice and WT mice, respectively, p=0.017). Tric-a KO mice showed limited heart rate changes to isoproterenol (24±6 and 99±15 bpm, n=9 and 10, Tric-a KO mice and WT mice, respectively, p&lt;0.001). In the action potential recordings, Tric-a KO atria showed only limited sinus rate changes to isoproterenol (35±9 and 71±10 bpm, n=8 and 6, Tric-a KO mice and WT mice, respectively, p=0.038). WT mice and Tric-a KO mice atrial contractile force showed dose-dependent changes in response to isoproterenol (10–100 nM), but Tric-a KO mice atria showed limited contractile force changes to isoproterenol (116 and 169%, n=7 and 6, Tric-a KO mice and WT mice, respectively, p&lt;0.01). In heart rate variability, Tric-a KO mice showed unstable RR intervals and longer standard deviation of RR intervals than WT mice. Conclusion Tric-a KO mice showed decreased cardiac pacemaking in the sinus node and attenuated responses to beta-adrenergic stimulus, which indicates the involvement of TRIC channels in cardiac rhythm formation and sympathetic nerve regulation.

Abstract 327: Attenuated Beta-Adrenergic Response in the Tric-a Knock Out Mice

Trimeric intracellular cation (TRIC) channels are expressed on the surface of sarcoplasmic reticulum (SR) and regulate calcium release from ryanodine receptors (RyRs). In a previous study, Tric-a knock out (KO) mice showed diminished calcium release from RyRs following increased calcium-influx via L-type calcium channels, which results in enhanced vascular resistance and non-dipper type hypertension. Decreased activation of RyR1 by PKA in skeletal myocytes in Tric-a KO mice is also known. However, physiological importance of TRIC channels on cardiac rhythm formation and its importance on the sympathetic nerve regulation are still obscure. Therefore, we aimed to clarify the effects of Tric-a ablation on cardiac pace making using Tric-a KO mice. We measured systolic blood pressure (SBP) with tail-cuff method, ECG and spontaneous action potential with microelectrode in the Tric-a KO and wild type (WT) mice. Isoproterenol or propranolol was used for sympathetic nerve manipulation. Furthermore, we evaluated heart rate variability (HRV). Tric-a KO mice tended to show limited responses to isoproterenol (0.3 mg/kg) than the WT mice (-27 ± 6 and -32 ± 6 mmHg, n = 10, p =0.70), and to propranolol (4 ± 6 and 13 ± 7 mmHg, n = 5~6, p =0.48). In ECG analysis, ablation of Tric-a gene resulted in significantly decreased heart rate changes to isoproterenol (23 ± 6 and 99 ± 15 bpm, Tric-a KO and WT mice, respectively, n = 9~10, p &lt;0.001). Response to propranolol was also significantly decreased in the Tric-a KO mice (-28 ± 20 and -122 ± 14 bpm, Tric-a KO and WT mice, respectively, n = 9~10, p &lt;0.001). In the action potential recordings, Tric-a KO mice showed significantly decreased sinus rate changes to 1 microM isoproterenol (35 ± 9 and 71 ± 10 bpm, Tric-a KO and WT mice, respectively, n = 6~8, p &lt;0.05). In HRV analysis, low-frequency/high-frequency (LF/HF) ratio tended to be lower in the Tric-a KO mice than the WT mice under the administration of isoproterenol (0.22 ± 0.31 and 0.65 ± 0.16 bpm, Tric-a KO and WT mice, respectively, n = 9~11, p =0.16), suggesting lower sympathetic nerve tonus in the Tric-a KO mice. In conclusion, our data indicates that Tric-a KO mice showed attenuated responses to beta-adrenergic stimulus, which indicates involvement of TRIC-A channels in sympathetic nerve regulation.

Abstract 108: Sympathetic Inhibition Prevents the Homing of Specific Memory T Cells to the Bone Marrow and the Development of Repeated Hypertension

Effector memory T cells (T EM cells) play a crucial role in hypertension. Formed during an initial blood pressure surge, T EM cells can reside in bone marrow (BM) in a quiescent state for prolonged periods. Upon re-exposure to a hypertensive stimulus, these cells can be reactivated and aggravate hypertension and renal damage. Hypertension is also associated with elevated sympathetic outflow. We hypothesized that sympathetic nerves promote accumulation and reactivation of hypertension-specific T EM cells in the BM. We performed unilateral superior cervical ganglionectomy (SCGx) in C57BL/6 mice, causing sympathectomy of the forelimb on the surgical side. After 2-week Ang II infusion (490 ng/kg/min s.c.), 5х10 6 BM cells from both the SCGx and control limbs were isolated and co-cultured with 0.5х10 6 dendritic cells from other hypertensive mice. We found 30% fewer CD8 + T cell proliferation in the SCGx BM than intact side (1.9±0.2 vs. 2.8±0.1х10 4 , p&lt;0.01), but no difference in CD4 + T cells. To study mechanisms involved in T cell homing, 10 7 pan T cells were isolated from CD45.2 mice after Ang II infusion and adoptively transferred to CD45.1 mice with unilateral SCGx. Flow cytometry indicated that 35% fewer donor CD8 + T EM cells homed to the SCGx than the intact BM 7 days after transfer (5.3±0.8 vs. 8.1±1.5 per 10 4 total T cells, p&lt;0.05). We further determined if systemic sympatho-inhibition during T cell homing is protective against future hypertensive stimuli. We blocked systemic sympathetic outflow by injecting an inhibitory designer receptor exclusively activated by a designer drug (Gi-DREADD) into the rostroventral lateral medulla (RVLM) and performed pan-T cell adoptive transfer 10 days later. The DREADD ligand CNO was given in drinking water 3 days before till 7 days after adoptive transfer. After washout, mice received low dose Ang II infusion (140 ng/kg/min) for 2 weeks. As measured by radiotelemetry, mice with control injection developed hypertension (160±7 mmHg). However, mice with Gi-DREADD expressed in RVLM remained normotensive (136±3 mmHg, p&lt;0.05 vs. control). These data define a novel role of sympathetic nerves in regulation of memory T cell trafficking, and sympathetic inhibition may have long term protective effect beyond lowering blood pressure.

The effect of circadian rhythm on the correlation and multifractality of heart rate signals during exercise

The heart rate variability (HRV) signals can well reflect the effect of exercise on cardiac autonomic nerve function, which can be used as the theoretical index for the development of the best physical exercise program. In this paper, we used multifractal detrended fluctuation analysis (MF-DFA), mass index spectrum and multifractality spectrum to analyze the heart rate variability signals, which have been obtained in these states, such as before, during and after exercise. The purpose is to establish the relationship between the nonlinear parameter of the signals and the autonomic nerve regulation, reveal the physiological mechanism for the effect of circadian rhythm. The result shows that exercise can decrease the correlation and increase the multifractality of heart rate variability signals. In different periods, the diversity of correlation and multifractality among different signals are obviously. The result shows that the correlation of heart rate variability signals was negatively correlated with sympathetic nerve regulation and positively correlated with vagus nerve regulation; the multifractality was positively correlated with sympathetic nerve regulation and negatively correlated with vagus nerve regulation. Further studies show that the function of heart system and the balance of autonomic nerve in the afternoon are more suitable for high-intense physical exercise.

Sympathetic Innervation Promotes Bone Marrow Homing of Specific CD8+ Effector Memory T Cells in Hypertension

We have recently identified a critical role of hypertension‐specific effector memory T lymphocytes (TEM cells) in the blood pressure elevation and renal dysfunction caused by repeated hypertensive stimuli. Formed during an initial immune challenge, TEM cells reside in the bone marrow (BM) in a quiescent state for prolonged periods, and can be reactivated upon re‐exposure to the hypertensive stimulus. Hypertension is associated with increased sympathetic outflow. We therefore hypothesized that sympathetic nerves regulate accumulation and reactivation of hypertension‐specific TEM cells in the BM. We performed unilateral superior cervical ganglionectomy (SCGx) in wild‐type C57BL/6 mice, causing selectively sympathectomy of the forelimb on the surgical side. After recovery, mice received Ang II infusion for two weeks. To determine the changes of T cells in the BM that were specific to hypertension, 5×106 BM cells were isolated from either the SCGx or control limbs, loaded with proliferation marker CFSE, and co‐cultured with 0.5×106 splenic dendritic cells isolated from another Ang II‐infused mouse. We found 30% less CD8+ T cell proliferation in the SCGx BM compared to control side (1.9±0.2 vs. 2.8±0.1×104, p&lt;0.001), but no difference in CD4+ T cells. To further study the effect of sympathetic nerves on BM T cell homing, 1×107 pan T cells were isolated from CD45.2+ wild‐type mice after Ang II infusion and adoptively transferred to CD45.1 mice that had previously undergone unilateral SCGx. Flow cytometry indicated that 7 days after transfer, 25% fewer CD8+ TEM cells from the hypertensive donors homed to the SCGx BM compared to the innervated BM (5.3±0.8 vs. 8.1±1.5 per 104 total T cells, p&lt;0.05), suggesting that sympathetic nerves regulate CD8+ TEM homing in the bone marrow at baseline condition. To study enhanced local sympathetic nerve activity in BM observed in hypertension, excitatory DREADD (designed receptor exclusively activated by designed drug) was expressed in the SCG on one side of mice by microinjection of adeno‐associated viral vector. Two weeks later, the animals received pan‐T cells adoptively transferred from hypertensive donors, and the specific ligand clozapine‐N‐oxide for DREADD was given in drinking water for 7 days. In contrast to denervation, augmenting sympathetic nerve activity increased CD8+ TEM homing by ~50% compared to the baseline level (14.9±2.7 vs. 9.3±2.3 per 104 total T cells, p&lt;0.01). These data define a novel role of sympathetic nerves in regulation of memory T cell trafficking in hypertension. Adrenergic blockade may be beneficial in disrupting survival of these injurious T cells, and thus might provide protection against repeated hypertensive stimuli known cause their reactivation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Acupuncture Application in Chronic Kidney Disease and its Potential Mechanisms.

Chronic kidney disease (CKD) is an increasing major public health problem worldwide. The number of CKD patients on hemodialysis is growing rapidly as well. Acupuncture technique is one of the traditional Chinese medicine methods and has been used in a variety of diseases. Nowadays, the clinical application of acupuncture technique for CKD patients has become the focus for its effectiveness and security. In this paper, we will review the therapeutic effects and mechanisms of different acupuncture techniques for CKD patients. In patients with CKD, acupuncture improves renal function, reduces proteinuria, controls hypertension, corrects anemia, relieves pain, and controls many hemodialysis-related complications such as uremic pruritus, insomnia and fatigue. The mechanisms are related to the regulation of sympathetic nerve and the activation of bioactive chemicals. In conclusion, acupuncture is proved to be beneficial for CKD patients. More research, however, is needed to verify the potential mechanisms.

Abstract 001: Sympathetic Innervation Promotes Bone Marrow Homing of Hypertension-specific CD8 + Effector Memory T Cells

We have recently identified a critical role of hypertension-specific effector memory T lymphocytes (T EM cells) in the blood pressure elevation and renal dysfunction caused by repeated hypertensive stimuli. Formed during an initial immune challenge, T EM cells reside in the bone marrow (BM) in a quiescent state for prolonged periods, and can be reactivated upon re-exposure to the hypertensive stimulus. Hypertension is associated with increased sympathetic outflow. We therefore hypothesized that sympathetic nerves regulate accumulation and reactivation of hypertension-specific T EM cells in the BM. We performed unilateral superior cervical ganglionectomy (SCGx) in wild-type C57BL/6 mice, causing selectively sympathectomy of the forelimb on the surgical side. After recovery, mice received Ang II infusion for two weeks. To determine the changes of T cells in the BM that were specific to hypertension, 5х10 6 BM cells were isolated from either the SCGx or control limbs, loaded with proliferation marker CFSE, and co-cultured with 0.5х10 6 splenic dendritic cells isolated from another Ang II-infused mouse. We found 30% less CD8 + T cell proliferation in the SCGx BM compared to control side (1.8±0.1 vs. 2.6±0.3х10 4 ), but no difference in CD4 + T cells. To further study the effect of sympathetic nerves on BM T cell homing, 1х10 7 pan T cells were isolated from CD45.2 + wild-type mice after Ang II infusion and adoptively transferred to CD45.1 mice that had previously undergone unilateral SCGx. Flow cytometry indicated that 7 days after transfer, 25% fewer CD8 + T EM cells from the hypertensive donors homed to the SCGx BM compared to the innervated BM (27.8±2.6 vs. 20.8±2.5 per 10 3 total BM cells). This effect was specific for hypertension as homing of OT-I T EM cells, which are responsive to ovalbumin, was not influenced by sympathectomy. Further adoptive transfer studies using mice lacking beta 2 adrenergic receptors (β2AR) indicate that β2AR in the bone marrow niche, rather than T cell β2AR is critical for T EM cell homing. These data define a novel role of sympathetic nerves in regulation of memory T cell trafficking, and this likely contributes to the predisposition to hypertension and end-organ damage for prolonged periods following an initial episode of hypertension.

Improvement in baroreflex control of renal sympathetic nerve activity in obese Sprague Dawley rats following immunosuppression.

This investigation explored the hypothesis that in obesity an inflammatory response in the kidney contributed to a renal nerve-dependent blunting of the baroreflex regulation of renal sympathetic nerve activity. Rats received a normal (12% kcal) or high-fat (45% kcal) diet for 8 weeks plus daily injections of vehicle (0.9% NaCl i.p) or tacrolimus (0.25 mg kg-1 day-1 i.p) from weeks 3-8. Following anaesthesia, left renal sympathetic nerve activity was recorded, baroreflex gain curves were generated, by infusing phenylephrine and sodium nitroprusside, and cardiopulmonary baroreceptors challenged by infusing a saline load. The high-fat diet elevated weight gain and adiposity index by 89 and 129% (both, P < 0.001). Mean blood pressure (132 ± 4 vs 103 ± 5 mmHg), fractional noradrenaline excretion and creatinine clearance (5.64 ± 0.55 vs 3.32 ± 0.35 mL min-1 kg-1 ) were 28, 77 and 69% higher (all P < 0.05), but urine flow and fractional sodium excretions were 42 and 72% (both P < 0.001) lower compared to normal rats. Plasma and renal TNF-α and IL-6 concentrations were fourfold to fivefold (P < 0.001) and 22 and 20% higher (both, P < 0.05), in obese rats but normalized following tacrolimus. In obese rats, baroreflex sensitivity was reduced by 80% (P < 0.05) but restored by renal denervation or tacrolimus. Volume expansion reduced renal sympathetic nerve activity by 54% (P < 0.001) in normal and obese rats subjected to renal denervation and tacrolimus, but not in obese rats with an intact renal innervation. Obesity induced a renal inflammation and pointed to this being both the origin of autonomic dysregulation and a potential focus for targeted therapy.

The Role of Lumbar Sympathetic Nerves in Regulation of Blood Flow to Skeletal Muscle during Anaphylactic Hypotension in Anesthetized Rats

During hypovolemic shock, skeletal muscle blood flow could be redistributed to vital organs via vasoconstriction in part evoked by activation of the innervating sympathetic nerve activity. However, it is not well known whether this mechanism operates during anaphylactic shock. We determined the femoral artery blood flow (FBF) and lumbar sympathetic nerve activity (LSNA) mainly regulating the hindquater muscle blood flow during anaphylactic hypotension in anesthetized rats. Anesthetized Sprague-Dawley rats were randomly allocated to the following groups (n = 7/group): (1) non-sensitized, (2) anaphylaxis, (3) anaphylaxis-lumbar sympathectomy (LS) and (4) anaphylaxis-sinoaortic denervation (SAD) groups. Anaphylaxis was induced by an intravenous injection of the ovalbumin antigen to the sensitized rats. The systemic arterial pressure (SAP), heart rate (HR), central venous pressure (CVP), FBF and LSNA were continuously measured. In the anaphylaxis group, LSNA and HR increased, while SAP and FBF decreased after antigen injection. In the anaphylaxis-SAD group, LSNA did not significantly change during the early phase, but the responses of SAP and FBF were similar to those in the anaphylaxis group. In the anaphylaxis-LS group, both FBF and SAP decreased similarly to the anaphylaxis group during anaphylactic hypotension. These results indicated that LSNA increased via baroreceptor reflex, but this sympathoexcitation or LS did not affect antigen-induced decreases in FBF or SAP. Lumbar sympathetic nerves are not involved in regulation of the blood flow to the hindlimb or systemic blood pressure during anaphylactic hypotension in anesthetized rats.

Modified sympathetic nerve regulation in AKAP5-null mice

Genetic analyses have revealed an important association between A-kinase anchoring proteins (AKAPs) and the intracellular calcium modulating system. AKAP5, also known as AKAP79/150, is an anchoring protein between PKA and voltage-dependent calcium channels, ryanodine receptor-2, phospholamban and other molecules.The aim of the present study was to elucidate the physiological importance of AKAP5 in the creation of cardiac rhythm using AKAP5-null mice.ECG analysis showed a normal sinus rhythm and a decreased responsiveness to isoproterenol in AKAP5-null mice compared with wild-type mice. Analysis of heart rate variability revealed that the R–R interval was unstable in AKAP5-null mutants and that the low-frequency components had decreased, indicating that the tonus of the sympathetic nervous system was affected. Furthermore, the atrium of the AKAP5-null mice showed a decreased positive inotropic response to isoproterenol, indicating the involvement of AKAP5 in a PKA-dependent pathway. Thus, our present study revealed that AKAP5 plays a significant role in the regulation of sympathetic nerve activities.

Heart rate variability predicts mortality in peritoneal dialysis patients

Background: The predictive value of heart rate variability (HRV) in peritoneal dialysis (PD) has never been tested. Methods: In this study, the associations between HRV measures and the mortality in 81 PD patients were analyzed. HRV was measured by using 5-min recordings of a stationary system by a standardized method. Both time domain and frequency domain parameters were analyzed. Results: During a follow-up period of 43.78 ± 14.77 months, 25 patients died, four patients were transferred to hemodialysis. Of the 81 patients, the time domain parameters, such as the standard deviation of differences between adjacent normal sinus to normal sinus (NN) intervals (SDSD) and the square root of the mean of the squared differences between adjacent normal NN intervals (RMSSD), were higher; the frequency domain parameters, such as the ratio of low-frequency power to high-frequency power (LF/HF) and the normalized LF, were lower, and the normalized HF was higher in the non-survived group as compared with the survived group. A Cox proportional hazards model analysis revealed that, of the HRV measures, decrease of the normalized LF, LF/HF and increase of rMSSD, SDSD, normalized HF had significant predictive value for mortality. After adjustment for other univariate predictors including age, urine volume, renal Kt/V, high-sensitivity C-reactive protein (hs-CRP), the predictive value of decreased LF/HF remained significant. Kaplan–Meier survival analysis showed mortality rate was much higher in patients with a low LF/HF (median value of 1.56). Conclusion: The decreases of LF/HF which reflects impaired sympathetic nerve regulation is an independent predictor of mortality in PD patients.

Involvement of the orexin system in sympathetic nerve regulation

Orexin, also known as hypocretin, is a secreted neuropeptide implicated in the regulation of sleep and food intake. In the present study, we examined the importance of orexin in regulation of the sympathetic nervous system using an orexin/ataxin-3 transgenic (OXTg) rat, which has a minimal number of orexin neurons.RT-PCR analysis identified expression of prepro-orexin and orexin receptor-1 (OX1R) in the superior cervical ganglion (SCG), and expression of another receptor (OX2R) was marginal in the wild-type rat. The orexin/ataxin-3 transgenic rat showed increased expression of OX1R and OX2R, whereas expression of prepro-orexin was undetectable, suggesting a compensatory increase in both receptors. In the ECG recording (R–R interval), orexin/ataxin-3 transgenic rats showed decreased responsiveness to the β-adrenergic blocker propranolol. Furthermore, OXTg rats had deteriorated R–R interval regulation, indicating involvement of the orexin system in sympathetic nerve regulation. This was accompanied by decreased baroreflex and responsiveness to β-adrenergic blocker in blood pressure recording, also suggesting involvement of the orexin system in sympathetic nerve regulation. Histological examination revealed hypotrophic changes in the transgenic heart, suggesting involvement of the orexin system in cardiac development. Taken together, our present results indicate involvement of the orexin system in sympathetic nerve control.

CHANGE OF ECG PARAMETERS DEPENDING ON THE LOAD LEVEL IN ATHLETES

The influence of physical training on bodies of athletes leads to changes that can be characterized as morphological, functional, electrophysiological and psychological. Dynamic exercise, such as running, swimming and riding a bicycle, leads to volume load of heart. Static exercise (gymnastics, weightlifting, wrestling) leads to the development of relatively large muscle force, with or without changes in muscle length and movement of the joint. Given the frequent number of sudden cardiac death cases in sport, it is important to distinguish between changes of the heart that occur as a result of adaptation to physical activity and changes due to some pathological conditions. The aim of this paper is to present the latest information on changes in ECG parameters depending on the load of athletes while performing aerobic trainings in order to better identify markers of adverse cardiovascular events, particularly sudden death in athletes. It is common to see on the ECG of athletes at rest hypertrophy of the left and right ventricle, interventricular conduction disorder, positive ST changes, and short-term tachycardia. Changes that occur in athletes are due to increased vagal tone and suppression of sympathetic nerve regulation. Many changes can be attributed to intrinsic cardiac component that is responsible for the lower frequency of athlete's heart deinnervation (with atropine or propranolol), which means that intense training influences how the autonomic regulation and the intrisic cardiac pacemaker function. It is common for athletes to have sinus bradycardia, sinus arrhythmia, first degree AV block and Mobitz I, as well as junctional rhythm, ST segment elevation, high and sharp, or biphasic T-waves, while ST depression or isolated T-wave inversion are less common. They can also have increased amplitude of P-wave and QRS complex, QRS axis rotation to the right and incomplete right branch block. Some but insufficient data tell about the presence of the third-degree AV block and atrial and ventricular ectopic beats and their predictive role for malignant rhythm disorders. Acta Medica Medianae 2012;51(3):5762.

Immunoreactivity for the NR1 subunit of the NMDA receptor occurs in spinally‐projecting catecholamine and serotonin neurons of the rat ventral medulla

Bulbospinal neurons in the ventral medulla play important roles in sympathetic nervous regulation. Current evidence suggests that these neurons are activated by NMDA and non‐NMDA subtypes of glutamate receptors. In this study, we examined bulbospinal neurons for the NR1 subunit of the NMDA receptor. Rats received bilateral injections of cholera toxin B (CTB) into spinal segment T9 to label bulbospinal neurons. Triple immunofluorescence was used to detect CTB (blue, AMCA), NR1 (red, Cy3) and either tyrosine hydroxylase (TH) or tryptophan hydroxylase (TpTH) (green, FITC). In the rostral ventrolateral medulla, NR1 occurred in both CTB+/TH+ neurons and CTB+ neurons. CTB+/TpTH+ neurons in raphé pallidus and the parapyramidal region also contained NR1. In addition, NR1 was present in occasional CTB+ neurons in raphé pallidus. These results show that the obligatory subunit of the NMDA receptor is expressed by spinally‐projecting C1 and non‐C1 neurons as well as spinally‐projecting serotonin neurons in raphé pallidus and the parapyramidal region. These receptors likely mediate at least some of the neuronal excitation in these regions in normal and pathological conditions. (R01‐ HL096787, NHMRC #480414).

A critical role of sympathetic nerve regulation for the treatment of impaired daily rhythm in hypertensive Dahl rats

There is a deep relationship between impaired circadian rhythm and hypertension. However, the detailed mechanisms between the daily sleep-wake rhythm and cardiovascular disorders have not yet been elucidated. To clarify the mechanism, we examined salt-sensitive Dahl rats that were fed normal chow (n=10), high-salt chow (n=10) and high-salt chow with bisoprolol (n=10). Simultaneous electroencephalogram, electromyogram and locomotor activity were examined to analyze the sleep-wake state. We also examined heart rate, blood pressure and echocardiographic findings to verify the presence of hypertension. Hypertension with impaired ventricular contraction was observed in the rats with high-salt-chow consumption whereas normal-chow rats did not show these disorders. Although rats with the normal diet showed a standard daily rhythm with normal rapid eye movement (REM) sleep duration and locomotor activity, the high-salt-diet group exhibited an impaired daily rhythm with suppressed REM sleep and significant abnormal locomotor activity. Bisoprolol significantly improved the daily sleep-wake rhythm and locomotor activity. We showed that an impaired daily rhythm was closely related to the development of hypertension. Regulation of sympathetic nerve alterations may have a key role in the treatment of hypertension and circadian rhythm disorder.

Does Infusion of Bacillus anthracis Toxins Produce Sympathoinhibition?

Bacillus anthracis infection is a pathophysiological condition that produces shock‐like cardiovascular alterations. Bacillus anthracis produces two endotoxins, lethal toxin (LeTx; lethal factor + protective antigen) and edema toxin. Neurological complications are a critical component of the pathology produced by Bacillus anthracis toxins, however, little is known about the effect of these toxins on sympathetic nerve regulation. We tested the hypothesis that infusions of Bacillus anthracis toxins alter sympathetic nerve discharge (SND). Splenic, renal, and adrenal SND were recorded in urethane‐chloralose anesthetized rats. Rats with intact or denervated arterial baroreceptors (SAD) received intravenous lethal factor (100 μg/kg) + protective antigen (200 μg/kg) (LeTx) or vehicle, infused at 0.5 ml/hr. Mean arterial pressure (MAP), heart rate (HR), and SND were recorded continuously (up to 6 hrs) before and during intravenous toxin or vehicle infusions. Results indicate that LeTx produced marked reductions in MAP and HR that occurred several hours after initiation of infusion. The reduction in MAP was accompanied by inhibition of SND in both baroreceptor‐intact and SAD rats, indicating LeTx‐induced dysregulation of SND. These preliminary data provide evidence suggesting that Bacillus anthracis toxins can alter regulation of sympathetic nerve outflow. Funding provided by NIH HL092392.

Modified autonomic regulation in mice with a P/Q-type calcium channel mutation

Recent genetic analyses revealed an important association between P/Q-type channels and hereditary neurological disorders. The α1 subunit of P/Q-type channels is coded by a single CaV2.1 gene. Since calcium entry via neuronal calcium channels is essential for neurotransmission, P/Q-type channels may play an important role in cardiac autonomic neurotransmission. To elucidate the physiological importance of P/Q-type channels in autonomic nerve control, we used rolling Nagoya ( tg rol ) mice, which have a mutation in the CaV2.1 gene and decreased P/Q-type channel currents with reduced voltage sensitivity. The tg rol mice demonstrated unmodified expression of other calcium channel subunits. Electrocardiogram and echocardiographic analyses revealed decreased heart rate. Furthermore, ω-agatoxin IVA, a P/Q-type channel inhibitor, decreased heart rate and ejection fraction only in wild-type mice, thus suggesting a significant involvement of P/Q-type channels in chronotropic regulation. Atrium contraction analyses revealed a minor but significant role for P/Q-type channels in sympathetic and parasympathetic nerve regulation.