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Chronic intermittent hypobaric hypoxia (CIHH) is known to have an anti-hypertensive effect, which might be related to modulation of the baroreflex in rats with renal vascular hypertension (RVH). In this study, RVH was induced by the 2-kidney-1-clip method (2K1C) in adult male Sprague-Dawley rats. The rats were then treated with hypobaric hypoxia simulating 5000 m altitude for 6 h/day for 28 days. The arterial blood pressure (ABP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were measured before and after microinjection of L-arginine into the nucleus tractus solitarii (NTS) in anesthetized rats. Evoked excitatory postsynaptic currents (eEPSCs) and spontaneous EPSCs (sEPSCs) were recorded in anterogradely-labeled NTS neurons receiving baroreceptor afferents. We measured the protein expression of neuronal nitric oxide synthase (nNOS) and endothelial NOS (eNOS) in the NTS. The results showed that the ABP in RVH rats was significantly lower after CIHH treatment. The inhibition of ABP, HR, and RSNA induced by L-arginine was less in RVH rats than in sham rats, and greater in the CIHH-treated RVH rats than the untreated RVH rats. The eEPSC amplitude in NTS neurons receiving baroreceptor afferents was lower in the RVH rats than in the sham rats and recovered after CIHH. The protein expression of nNOS and eNOS in the NTS was lower in the RVH rats than in the sham rats and this decrease was reversed by CIHH. In short, CIHH treatment decreases ABP in RVH rats via up-regulating NOS expression in the NTS.
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Animals , Male , Baroreflex , Physiology , Blood Pressure , Hypertension , Metabolism , Hypoxia , Kidney , Metabolism , Nitric Oxide Synthase Type I , Metabolism , Rats, Sprague-Dawley , Solitary Nucleus , MetabolismABSTRACT
Objective To assess the left ventricular systolic function after renal sympathetic denervation(RSD) in beagles with heart failure by layer-specific two-dimensional speckle tracking imaging.Methods Twenty-three beagles were randomly divided into control group (8 dogs),URSD group (8 dogs)and RSD group (7 dogs).Control group was implanted with pacemakers without pacing,URSD group was implanted with pacemakers and underwent 3 weeks of rapid right ventricular pacing,and RSD group underwent catheter-based RSD bilaterally and was simultaneously implanted with pacemakers.All standard measurements were obtained from the left ventricular short-axis views at the levels of mitral annulus,papillary muscle and apex,and apical four-chamber,two-chamber,and long-axis views.The peak systolic longitudinal strain and circumferential strain of each layer of the left ventricle were measured by layerspecific two-dimensional speckle tracking imaging.Results After 3 weeks,all of the dogs in both the URSD and RSD groups showed lower left ventricular diastolic and systolic function compared with those in the control group,however,the dogs in the RSD group had a higher LV ejection fraction (LVEF) than the dogs in the URSD group(P ＜ 0.05).Compared with the control group,the global longitudinal strain,circumferential strain and radial strain all decreased significantly in URSD and RSD groups.The longitudinal strain of endo-and mid-cardium and the circumferential strain in endo-cardium were significantly higher in RSD group than those in URSD group(P ＜0.05).Conclusions Myocardial systolicfunction is impaired in dogs with heart failure,layer-specific two-dimensional speckle tracking imaging can provide effective tools to assess the left ventricular systolic function.Renal sympathetic denervation can improve the myocardial systolic function in dogs with heart failure.
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[ ABSTRACT] AIM: To evaluate the guiding effect of high-frequency stimulation ( HFS) on renal denervation ( RDN) , and to compare the similarities and differences of blood pressure changes at the time of electrical stimulation and radiofrequency ablation .METHODS:A total of 6 Kunming dogs were included in this study .Renal artery abnormalities were excluded by angiography .High-frequency stimulation and radiofrequency ablation were performed at the same sites from distal to proximal segments of the renal artery .Invasive blood pressure ( BP) was recorded during the whole proce-dure.The change of the blood pressure was analyzed .HE and Masson staining was adopted to detect the structural changes in the wall of the renal artery and surrounding tissues .The immumohistochemical staining for tyrosine hydroxylase ( TH) was used to observe the renal nerve damage after ablation .RESULTS: Electrical stimulation and radiofrequency ablation were delivered in a total of 50 sites.The BP increasing response was induced at 34%sites (n=17), while the rest sites (66%, n=33) had no response.Compared with the baseline , HFS caused the increases in systolic BP of (0.34 ±3.38), (0.41 ±3.04), (10.47 ±5.73), (13.27 ±3.63), (10.17 ±1.87) and (0.78 ±1.87) mmHg in 6 serial 20 s time segments during 120 s of HFS at positive BP response sites .Similarly, the increases in systolic BP by (-0.88 ±3.44) , (-1.64 ±3.47), (13.17 ±3.12), (12.82 ±3.21), (9.50 ±2.68) and ( -6.09 ±2.21) mmHg were observed dur-ing 120 s of ablation procedure at the same sites in 6 serial 20 s time segments .At non-responding sites , HFS and ablation failed to cause a significant increase in systolic BP .The mean area of nerves in the response sites was ( 0.51 ±0.28 ) mm2, whereas that in non-response sites was (0.09 ±0.06) mm2(P<0.01).The average absorbance values of TH in re-nal nerves at ablation and non-ablation sites were 0.031 ±0.015 and 0.085 ±0.018 ( P <0.01 ) , respectively . CONCLUSION:Renal sympathetic nerves can be effectively mapped by HFS .Radiofrequency ablation guided by HFS is valid to injure sympathetic nerves around renal artery .
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AIM:To investigate the effect of renal denervation ( RDN) by radiofrequency catheter ablation on the expression of aquaporins ( AQP) in dog kidneys .METHODS:Adult Chinese Kunming dogs ( n=12 ) were randomly divided into RDN group and control group (6 for each group).The dogs in RDN group underwent bilateral RDN using ra-diofrequency catheter ablation , and radiofrequency catheter was positioned in bilateral renal artery without ablation in con -trol group.The levels of norepinephrine (NE) and AQP1~3 in the renal tissues were detected 1 month after RDN, and blood pressure (BP) measurements were performed at baseline and 1 month after RDN.RESULTS: The level of NE in RDN group was significantly lower than that in control group (P<0.01).The expression of AQP1~3 in the renal cortex and medulla was lower in RDN group than that in control group .RDN also caused a substantial BP reduction (P<0.05). CONCLUSION:RDN substantially decreases the tissue levels of NE and AQP in dog kidneys , and also decreases BP sig-nificantly , which might be involved in the mechanism of BP reduction by RDN .Renal sympathetic nerve plays an excitatory role in the regulation of AQP in the kidney.
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Objective To evaluate the effects of transcatheter renal sympathetic denervation (RSD) on the cardiac systolic function of dogs with pulmonary arterial hypertension(PAH)using two-dimensional speckle tracking imaging (2D-STI).Methods Twenty two dogs were divided in to three groups:control group (n=7),PAH group (n =8),PAH+RSD group(n =7).Pulmonary artery hypertension models were made by monocrotaline injection in PAH group and PAH+RSD group,while bilateral renal artery sympathetic nerve were also ablated in PAH+RSD group.Meanwhile,sham operation treatment were made in the control group and PAH group.The changes of blood pressure and cardiac indicies of ultrasound were observed before and after 8 weeks respectively.Then the left ventricular(LV)lateral strain,septal strain (IVS LS)and right ventricular(RV)strain were calculated.In the apical 4-chamber view,time from QRS onset to peak systolic strain in each the six segments of the LV and RV were measured and standard deviation of the time to peak longitudinal strain of six segments (LVTsl-6SD and RVTsl-6SD)were calculated.LV twist degree were obtained from LV rotation curve in basal and apical short-axis planes. Results After 8 weeks,there was no difference in the mean strain of LV lateral wall among the three groups,while the mean strain of RV lateral wall and septal were higher in PAH+RSD group than the PAH group [(18.91±0.86)% % vs 16.34±1.36)%,P <0.001;(18.39±1.03)% vs (17.02±1.00)%,P <0.001,respectively].Compared with PAH group,LVTsl-6SD and RVTsl-6SD of PAH + RSD group decreased significantly [(25.45±3.59)ms vs (40.40±2.83)ms,P <0.001;(34.16±2.81)ms vs (51.98± 3.64)ms,P <0.001,respectively].The LV twist degree of PAH+RSD group increased significantly[(10.47± 0.73)°vs (8.46±1.06)°,P <0.001].Conclusions RSD can reduce the influence of pulmonary artery hypertension on cardiac systolic function.
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Transcatheter renal sympathetic denervation with radiofrequency ablation has become a new treatment for refractory hypertension.Recent studies have showed that renal sympathetic denervation can also treat the diseases that are related to increased sympathetic nerve activity, such as metabolic diseases, cardiac disfunction, arrhythmia, obstructive sleep apnea syndrome, polycystic ovary syndrome, renal failure, etc. This paper aims to make a general review on the recent clinical research progress about renal sympathetic denervation with radiofrequency ablation.
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Objective To evaluate the synchrony of heart after catheter-based renal denervation by two dimensional speckle tracking imaging.Methods Each renal sympathetic nerve of 20 dogs were ablated,and the index of heart and blood pressure were detected 6 weeks later.Standard 2D images were acquired in the 2-,3-and 4-apical views.The times from QRS onset to peak-systolic strain rate and to peak-diastolic strain rate were measured for the longitudinal 16-segments in Qlab software,and the standard deviation were calculated.The time to peak longitudinal strain rate and time to peak contraction strain rate of left atrium were measured for each segment contained septal,latera,anterior and posterior in the level of the basal segments,middle sections and apical in Qlab software,and the standard deviation were calculated.Parameters were compared among the before and after of the ablation.Results The systolic pressure and diastolic pressure had no changes after the ablation of renal sympathetic nerve (P ＞ 0.05).The R-R showed a increasing trend,but no significant differences(P ＞0.05).The peak time of LV systolic and diastolic strain rate had a extended trendency too,but no differences(P ＞0.05),and standard deviations of the peak times had no significant differences(P ＞0.05).The peak time of LA longitudinal strain rate and contraction strain rate had a extended trendency,but no obvious change (P ＞0.05),and the standard deviations of the peak times had no significant differences (P ＞0.05).The size of the heart cavity had no differences(P ＞0.05).Conclusions The systolic pressure and diastolic pressure have no changes after the ablation of renal sympathetic nerve,and the synchrony parameters of LV and LA have no significant differences,demonstrate that the synchrony of heart is not affected by the renal sympathetic denervation.
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AIM:Left coronary artery ligation(LAD)was used to induce heart failure.Losartan was microinjected into paraventricular nucleus(PVN),heart rate(HR),blood pressure(BP)and renal sympathetic nerve activity(RSNA)were measured.The mechanism of PVN in chronic heart failure was investigated.METHODS:Sprague-Dawley male rats were selected for LAD ligation for heart failure models,the variation of cardiac function was detected by echocardiography.Losartan was microinjected into PVN,the responses of HR,BP and RSNA were analyzed.RESULTS:Compared with sham group,the level of LV was increased(P