Beneficial effect of atorvastatin on left ventricular remodeling in spontaneously hypertensive rats

This study was designed to investigate whether atorvastatin has a beneficial effect on left ventricular (LV) remodeling in spontaneously hypertensive rats (SHR), and then explore the underlying mechanisms involved. 12 SHRs were randomized to receive either distilled water (SHR group, n = 6) or atorvastatin (ATV group, n = 6) for 10 weeks. Age-matched Wistar-Kyoto rats (WKY) gavaged by distilled water were used as normal controls (WKY group, n = 6). By using these rats, we observed the effects of atorvastatin on LV hypertrophy and fibrosis, and investigated atorvastatin-induced cell apoptosis and p27 protein expression. In addition, the serum lipid concentration and blood pressure level were also measured in this study. 10 weeks later, a significant decrease in the cardiosomatic ratio, LV weight to body weight ratio and cardiomyocyte transverse diameter, as well as myocardial hydroxyproline and collagen content was observed in the atorvastatin-treated SHR. In addition, atorvastatin increased the positive rate of cell apoptosis and p27 protein expression. A decreased serum lipid concentration and a reduced systolic blood pressure level were also found in the atorvastatin-treated SHR. These findings demonstrated a beneficial effect of atorvastatin on adverse LV remodeling in SHR, and the induction of cell apoptosis and upregulation of p27 protein may serve as the underlying mechanisms of this action.

Effects of Astragalus membranaceus and its main components on the acute phase endothelial dysfunction induced by homocysteine

OBJECTIVE

This study was designed to investigate the effects of Astragalus membranaceus (AM) and its main components, astragalus saponin (ASP), astragalus polysaccharide (APS) and aminobutyric acid (GABA), on homocysteine (Hcy) induced acute impairment of vascular tone and to explore whether the antioxidant mechanism was involved in AM protective effect.

METHODS

Inhibitory effects of Hcy and protective effects of AM and its main components on endothelium-dependent relaxation of aortic rings were determined by isometric tension recordings and nitric oxide signaling was assayed with 125I-cGMP RIA Kit. Furthermore, generation of reactive oxygen species (ROS) in endothelial cells was detected using 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCF-DA).

RESULTS

Hcy significantly inhibited endothelium-dependent relaxation to acetylcholine (ACh) in a dose-dependent manner, and decreased cGMP levels increased by ACh in aorta. Furthermore, superoxide dismutase (SOD), AM, and ASP markedly attenuated inhibition of vasorelaxation and downregulation of cGMP level by Hcy, and APS exerted a tendency to reverse both of the depressive responses, while GABA had no similar effects. Additionally, partially impaired relaxation by Hcy was completely blocked due to the presence of N(omega)-nitro-L-arginine-methyl ester (L-NAME), which could not be further altered by treatment with AM, ASP, APS or GABA. Finally, Hcy significantly increased intracellular ROS levels in endothelial cells as measured by CM-H2DCF-DA fluorescence. SOD, AM, ASP, and APS, but not GABA, inhibited Hcy-stimulated ROS generation.

CONCLUSION

This study demonstrated that AM and ASP, potently protected endothelium-dependent relaxation against the acute injury from Hcy through nitric oxide regulatory pathways, in which antioxidation played a key role.

rAAV-mediated angiogenin gene transfer induces angiogenesis and modifies left ventricular remodeling in rats with myocardial infarction

In vitro studies have demonstrated that bovine angiogenin (ANG) significantly stimulates both the migration of endothelial cells and the formation of tubelike structures. The aim of this study was to explore whether ANG gene transfer could enhance vascularization, modify left ventricular remodeling, and attenuate cardiac dysfunction in rats with myocardial infarction (MI). We constructed a recombinant adeno-associated virus vector encoding the ANG gene (rAAV-ANG) and evaluated its angiogenic potential after regional transfection by intramyocardial injection immediately after left anterior descending artery ligation in rats. Four weeks after coronary artery ligation, rAAV-ANG transfection upregulated the myocardium ANG protein expression level in both normal and MI rats, and immunohistochemistry showed that the overexpressed ANG was distributed in the cytoplasm of cardiomyocytes. In rats with MI, rAAV-ANG treatment altered left ventricular remodeling, as indicated by a decrease in left ventricular end diastolic diameter, left ventricular end systolic diameter, cardiomyocyte diameter, ventricular weight to body weight ratio and interstitial fibrosis infiltration. We also found an increase in capillary density and partly restored cardiac function in the group receiving rAAV-ANG treatment. These results confirmed that in rats with MI, ANG gene transfer could induce angiogenesis, alter left ventricular remodeling, and attenuate cardiac dysfunction. This study provides a new choice of treatment for ischemic heart disease.

[The changes in the mRNA levels of calcium regulatory proteins in ischemia/reperfusion rat ventricles]

AIM

To investigate the changes in the expression of four kinds of calcium regulatory proteins mRNA on the isolated ischemia/ reperfusion (IR) hearts.

METHODS

The rat hearts were divided into two groups: control group and IR group which received 45 min exposure to Krebs-Henseleit solution after 15 min zero-flow global ischemia. The indexes of left ventricular function, such as LVDP, +dp/dt(max), -dp/dt(max), and an arrhythmia scoring system were compared between the two groups. The messenger ribonucleic acid (mRNA) amount of sarcoplasmic reticulum (SR) Ca2+ ATPase (SERCA), phospholamban (PLB), inositol 1,4,5-trisphosphate receptor2 (IP3R2) and ryanodine receptor2 (RyR2) was measured by reverse transcription-polymerase chain reaction (RT-PCR) and normalized to the mRNA levels of beta-actin.

RESULTS

In the IR group, LVDP, +dp/dt(max) and -dp/dt(min) of the isolated hearts were depressed and the high rate of arrhythmias occurred during reperfusion. The levels of SERCA, IP3R2, RyR2 mRNA were lower in the IR isolated hearts group than those in the control group, while there was no difference in the level of phospholamban.

CONCLUSION

These data suggest that myocardial ischemia/reperfusion can induce the depression of cardiac performance and an increased risk of arrhythmias, concomitant with the decrease in SERCA, IP3R2, RyR2 mRNA steady state levels.

Effects of simvastatin on cardiohemodynamic responses to ischemia–reperfusion in isolated rat hearts

Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has long been thought to exert its benefits by reducing cholesterol synthesis, and has been shown to significantly reduce cardiovascular events and mortality in patients with or without coronary artery disease. However, it is still unknown whether acute administration of simvastatin beneficially affects the cardiac function prior or during ischemia-reperfusion. The aim of this study is to evaluate the cardioprotective effect of acute simvastatin treatment on isolated rat hearts or isolated ischemia-reperfusion hearts. Hearts were isolated from male Sprague-Dawley rats and attached to a Langendorff apparatus. The isolated hearts with or without ischemia (15 min) and reperfusion (60 min) were perfused with different concentrations of simvastatin. The parameters of cardiac function (such as left ventricular developed pressure [LVDP], +dp/dt max, and -dp/dt max), heart rate, and coronary flow were recorded. Simvastatin (3-30 micromol/l) significantly increased LVDP, +dp/dt max, and -dp/dt max in isolated rat hearts perfused for 60 min. Heart rate was depressed by 30 micromol/l simvastatin and the coronary flow was increased by 10 and 30 micromol/l simvastatin. At a concentration of 100 micromol/l simvastatin, worsening of heart function and subsequent cardiac arrest occurred. Administration of simvastatin (3-30 micromol/l) significantly preserved cardiac function detected by LVDP, +dp/dt max, and -dp/dt max in the isolated ischemia/reperfused (15/60 min) rat hearts. Simvastatin also significantly decreased heart rate at 30 micromol/l, and increased coronary flow at 10 and 30 micromol/l in these rat hearts. However, the protective effect of simvastatin reverted to increased damage at 100 micromol/l. Only 3 micromol/l simvastatin pretreatment before 15/60 min ischemia-reperfusion altered LVDP, +dp/dt max, and -dp/dt max. Both heart rate and coronary flow were unaltered after simvastatin pretreatment. Since simvastatin at a concentration lower than 100 micromol/l exerted beneficial effects on cardiac function in isolated perfused rat hearts, it could be applied just after myocardial ischemia and reperfusion.

Decreased cardiac sarcoplasmic reticulum Ca2+-ATPase activity contributes to cardiac dysfunction in streptozotocin-induced diabetic rats

Diabetic cardiomyopathy is characterized by reduced cardiac contractility due to direct changes in myocardium function independent of vascular disease. This study is to investigate the alterations of cardiac sarcoplasmic reticulum Ca2+ -ATPase activity and cardiac function in streptozotocin-induced diabetic rats. Diabetes mellitus (DM) was induced in male Wistar rats by intraperitoneal injection of streptozotocin. The activity of myocardium sarcoplasmic reticulum Ca2+ -ATPase and the left ventricular hemodynamic parameters were measured in DM rats 4 weeks, 6 weeks and 8 weeks after streptozotocin was administered. Phospholamban mRNA expression was detected by reverse transcription-polymerase chain reaction, and the protein levels of phospholamban and sarcoplasmic reticulum Ca2+ -ATPase were determined by Western blot. Normal rats served as control group. It was found that in DM rats 4 weeks after streptozotocin injection, the cardiac function, myocardium sarcoplasmic reticulum Ca2+ -ATPase activity, phospholamban mRNA and phospholamban protein were not significantly changed compared with those in the control rats. At 6 and 8 weeks after the streptozotocin injection, DM rats showed a significant decrease in sarcoplasmic reticulum Ca2+ -ATPase activity and cardiac function, as indicated by an increase of LVEDP and a marked depression in LVSP and +/- dP/dtmax. At the same time points, increases in phospholamban mRNA and protein levels were observed in DM rats. Sarcoplasmic reticulum Ca2+ -ATPase protein level showed no significant alterations in all DM rats compared with that in control rats. Our work confirms that sarcoplasmic reticulum Ca2+ -ATPase activity is depressed in rats with streptozotocin-induced DM, which is accompanied by elevated phospholamban protein level thus contribute to the pathogenesis of cardiac dysfunction in diabetic rats.

The analysis of ultrastructure and gene expression of sarco/endoplasmic reticulum calcium handling proteins in alloxan-induced diabetic rat myocardium

OBJECTIVE

The change of mechanical properties of isolated diabetic rat papillary muscle, myocardial ultrastructure and gene expression of sarco/endoplasic reticulum calcium handling proteins in alloxan-induced diabetic rat heart was investigated.

METHODS

Diabetes was induced in male Sprague-Dawley rats (180-220 g) by administering a single tail-vein injection (40 mg/kg) of alloxan. The control group was injected with normal saline. At the end of 2, 4 and 6 weeks after the induction of diabetes, the right ventricular papillary muscles were isolated and perfused with oxygen saturated Tyrode solution for assessment of the contractile function. Light and electron microscopic analysis was used to analyse the myocardial ultrastructure in rats six weeks after induction. Gene expression of calcium handling proteins was measured by reverse transcription-polymerase chain reaction and Western blot.

RESULTS

In the diabetic rats, +dT/dtmax and -dT/dtmax were decreased (P < 0.01), while 1/2 diastolic intervals were longer than control at the end of 4 and 6 weeks (P < 0.01). Electron microscopic analysis of the myocardium revealed a spectrum of subcellular remodelling which was characterized by damaged myofibrils and mitochondria and dilated swollen sarcoplasmic reticulum. The levels of both mRNA and protein of phospholamban were significantly increased, whereas 1, 4, 5-trisphophate inositol receptor type 2, ryanodine receptor type 2 mRNAs were significantly decreased compared with that in the age-matched 6 weeks control rats. In contrast, levels of both mRNA and protein of sarco/endoplasic reticulum Ca2+ -ATPase were not affected.

CONCLUSIONS

Contractile dysfunction of papillary muscles and subcellular remodelling exist in alloxan-induced diabetic rat myocardium. Up-regulation of phospholamban and down-regulation of sarco/endoplasic reticulum calcium release channel may be the molecular mechanism.

[Enhanced reporter gene transfer and expression in cardiac myocytes mediated by ultrasonic destruction of the microbubbles]

AIM

To determine if the diagnostic ultrasound and self-made microbubbles could be used to increase gene transfection and expression in cardiac myocytes by means of the ultrasound-mediated microbubbles destruction.

METHODS

The perfluoropropane-exposed sonicated dextrose albumin(PESDA) microbubbles were made and mixed with indicated volume reporter gene encoding beta-galactosidase prior to gene transfection. Gene transfection into the cultured cardiac myocytes was performed by exposure to the various intense diagnostic ultrasound (1.3 MHz) in the presence of the gene-attached microbubbles. The calcium phosphate precipitation gene transfection was carried out alone or in combination with ultrasound-mediated destruction microbubbles. The cells were harvested 48 h after transfection and beta-galactosidase expression was detected by in situ staining and quantitive assay.

RESULTS

Cardiac myocytes exposed to ultrasound with PESDA induced significantly increase in gene expression (60-fold compared with naked plasmids transfection, P < 0.01). Moreover, it was found that the reporter gene expression not only related with ultrasound intension but also with the microbubbles concentration. In combination with calcium phosphate precipitation gene transfection, ultrasound-mediated destruction microbubbles resulted in more intense gene expression even 6 hours after calcium phosphate precipitation gene transfection.

CONCLUSION

The ultrasonic destruction of gene-loaded microbubble is a highly effective gene transfer method, and it not only acts on the gene entry into cells, but also on the intracellular exogenous DNA expression.

Characteristics of the beta myosin heavy chain gene Ala26Val mutation in a Chinese family with hypertrophic cardiomyopathy

BACKGROUND

Genotype-phenotype studies have suggested that some mutations of genes encoding various components of the cardiac sarcomere cause hypertrophic cardiomyopathy (HCM) and are associated with the prognosis of patients with HCM. The aims of this study were to investigate the gene mutations of exons in the cardiac beta myosin heavy chain (MYH7) gene, the troponin T (TNNT2) gene, and the brain natriuretic peptide (BNP) gene, as well as to assess the effect of these mutations on the clinical features of Chinese patients with HCM.

METHODS

Five unrelated Chinese families with HCM were studied. Exons 3 and 18 in the MYH7 gene, exon 9 in the TNNT2 gene, and all three exons in the BNP gene were screened with the polymerase chain reaction (PCR) for genomic DNA amplification. Further study included purification of PCR products and direct sequencing of PCR fragments by fluorescent end labeling.

RESULTS

A C-to-T transition in codon 26 of exon 3 in the MYH7 gene was found in one family (including four patients and five carriers), resulting in an amino acid substitution of valine (Val) for alanine (Ala). The Ala26Val mutation was of incomplete dominance (penetrance 44%). This mutation was not seen in the other four families or in the control group. Moreover, the association between the gene mutations of exon 18 in MYH7, of exon 9 of TNNT2, and of all three exons in BNP and HCM was not found in the populations we studied.

CONCLUSIONS

The missense mutation Ala26Val found in this one Chinese family was associated with a mild phenotype of HCM. The genetic and phenotypic heterogeneity of HCM exists in the Chinese population. It suggests that genetic and environmental factors may be involved in the pathogenesis of HCM.

Effect of β-Blockers on Cardiac Function and Calcium Handling Protein in Postinfarction Heart Failure Rats

OBJECTIVES

The normal expression of Ca2+-handling protein is critical for efficient myocardial function. The present study was designed to test the hypothesis that beta-blocker treatment may attenuate left ventricular (LV) remodeling and cardiac contractile dysfunction in the failing heart, which may be associated with alterations of Ca2+-handling protein

METHODS

We investigated the change of LV remodeling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 mg/kg/d) or metoprolol (60 mg/kg/d) treatment for 6 weeks (n = 9 in the MI plus carvedilol group, and n = 8 in every other group). The expression of messenger RNA and proteins of sarcoplasmic reticulum Ca2+-adenosine triphosphatase (SERCA) and phospholamban in cardiomyocytes of all rats were also measured

RESULTS

There was significant LV remodeling and cardiac contractile dysfunction in MI rats. The messenger RNA and protein expression of SERCA were down-regulated (p < 0.01), but the expression of phospholamban messenger RNA and protein were up-regulated (p < 0.01) in MI rats compared to sham-operated rats. After the treatment with beta-blockers, LV remodeling and function were clearly improved. Carvedilol was better in attenuating the weight of the LV and the relative weight of the right ventricle than metoprolol (p < 0.05). beta-Blockers restored the low expression of SERCA (p < 0.05) but showed no effect on phospholamban expression (p > 0.05). Moreover, carvedilol induced a more significant improvement of SERCA expression than metoprolol (p < 0.05)

CONCLUSIONS

Beta-blockers are effective in preventing LV remodeling and cardiac contractile dysfunction in the failing heart. The molecular mechanism may be related to normalization of SERCA expression.

COMPARISON OF LOW and HIGH DOSES OF CARVEDILOL ON RESTORATION OF CARDIAC FUNCTION and CALCIUM-HANDLING PROTEINS IN RAT FAILING HEART

1. The beta-adrenoceptor antagonist carvedilol reverses cardiac dysfunction in the failing heart. A recent study showed that beta-adrenoceptor antagonists indirectly normalize Ca(2+)-regulatory proteins. The relationship between these two phenomena and the suitable dosage of carvedilol remains unclear. 2. We investigated the change in left ventricular (LV) remodelling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 or 2 mg/kg per day) treatment for 6 weeks. The expression of mRNA and proteins of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and phospholamban (PLB) in cardiomyocytes was also measured. 3. There was significant LV remodelling and cardiac contractile dysfunction in MI rats. The expression of SERCA mRNA and protein were downregulated (P < 0.01), but the expression of PLB mRNA and protein were upregulated (P < 0.01) in MI rats compared with sham-operated rats. After treatment with carvedilol, LV remodelling and cardiac contractile dysfunction were clearly improved. Low-dose carvedilol was better at improving some parameters of LV remodelling and function than the high dose. Carvedilol partially restored the low expression of SERCA (P < 0.05), but had no effect on PLB expression (P > 0.05). Moreover, low-dose carvedilol induced a more significant improvement in SERCA expression than did the high dose (P < 0.05). 4. The results of the present study suggest that carvedilol is effective in improving LV remodelling and cardiac contractile dysfunction after MI. This may be related to the normalization of SERCA expression.

Captopril Administered at Night Restores the Diurnal Blood Pessure Rhythm in Adequately Controlled, Nondipping Hypertensives

The aim of our study was to evaluate whether captopril administered at night, can shift the circadian blood pressure (BP) from a nondipper to a dipper pattern in adequately controlled hypertensive patients, who continued their antihypertensive therapy. In a prospective, randomized, double blind, placebo-controlled designed study, we enrolled 121 treated, adequately controlled nondipping hypertensive patients. All patients were randomly assigned to 12.5 mg captopril or placebo treatment administered at night. In case of nondippers, the dosage of captopril or placebo was doubled after two weeks of treatment, while for dippers antihypertensive regimens were not changed. After another two weeks, all patients underwent ambulatory BP monitoring. Our results show that at the end of the active treatment period, the prevalence of a dipping diurnal BP pattern in the captopril group (70%) was significantly higher than that in the placebo group (9.8%, P < 0.001). Nighttime BP, night/day BP ratio, nighttime BP load and 24-h systolic BP were significantly lower after 4 weeks nighttime captopril treatment compared to baseline. In conclusion, the present study demonstrates for the first time that captopril administered at night can restore the diurnal BP rhythm and decrease the elevated night/day BP ratio in appropriately controlled, nondipper hypertensive patients. These results were mainly due to the decrease of nighttime BP.

Diphasic Effects of Astragalus membranaceus BUNGE (Leguminosae) on Vascular Tone in Rat Thoracic Aorta

This study was designed to investigate the effects of the aqueous ethanol extract of Astragalus membranaceus BUNGE (Leguminosae) on rat thoracic aorta. Isometric tension was recorded in response to drugs in organ bath. In endothelium-intact aortic rings, A. membranaceus extract induced a significant dose-dependent relaxation of the rings precontracted by phenylephrine, which could be inhibited by preincubation with L-N(omega)-nitro-arginine methyl ester or methylthioninium chloride. In endothelium-denuded ones, the extract could dose-dependently relax the rings contracted by phenylephrine, not by KCl; and it could also attenuate contractile response to phenylephrine, not to caffeine or phorbol-12,13-diacetate in Ca(2+)-free medium; but it failed to affect the CaCl(2)-induced enhancement of contractile response to phenylephrine in Ca(2+)-free medium. These results indicate that nitric oxide signaling and Ca(2+)-handling pathway are involved in the A. membranaceus extract-induced vasodilatation.

A Novel Bursting Mechanism of Type A Neurons in Injured Dorsal Root Ganglia

Using intracellular recording in vivo, the bursting behaviors were investigated in the neurons of chronically compressed dorsal root ganglia of the adult rat. In most cases, the first spike of a burst emerged from amplitude-increasing damped subthreshold membrane potential oscillation (SMPO) and the discharge terminated by an amplitude-decreasing damped SMPO. The rhythms of these bursting behaviors are all irregular. Since some researchers found that the stochastic dynamics can also produce similar bursting pattern, the deterministic dynamics of interevent interval (IEI) series obtained from raw membrane potential recording was detected by extraction of the hierarchy of unstable periodic orbits (UPOs) in the windowed IEI series. The results showed a number of statistically significant UPOs of order-one, order-two, and order-three. These orbits form a complex but predictable lattice of regions in which the dynamics of the bursting occurrence is deterministic. Based on a complete classification scheme, the investigated bursting can be depicted by the elliptic bursting dynamics. The significance of the finding that a neuron in the injured dorsal root ganglion has such dynamics is also discussed.

Effects of homocysteine on number and activity of endothelial progenitor cells from peripheral blood

The aim of this study is to investigate whether homocysteine (Hcy) has influences on endothelial progenitor cells (EPCs) number and activity. Total mononuclear cells (MNCs) were isolated from peripheral blood by Ficoll density gradient centrifugation, and then the cells were plated on fibronectin-coated culture dishes. After 7 d cultured, attached cells were stimulated with Hcy (to make a series of final concentrations: 10, 50, 100 and 200 micromol/l) or vehicle control for the respective time points (6, 12, 24 and 48 h). EPCs were characterized as adherent cells double positive for DiLDL uptake and lectin binding by direct fluorescent staining under a laser scanning confocal microscope. EPCs proliferation, migration and in vitro vasculogenesis activity were assayed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, modified Boyden chamber assay and in vitro vasculogenesis kit, respectively. EPCs adhesion assay was performed by replating those on fibronectin-coated dishes, and then adherent cells were counted. Incubation of isolated human MNCs with Hcy dose and time dependently decreased the number of EPCs, maximum at 200 micromol/l, 24 h (approximately 50% reduction, P < 0.01). In addition, Hcy dose and time dependently impaired EPC proliferative, migratory, adhesive and in vitro vasculogenesis capacity. In conclusion, hyperHcy may induce the reduction of EPCs with decreased functional activity.

[Serum levels of soluble Fas soluble Fas ligand and soluble IL-2 receptor in patients with coronary heart disease]

OBJECTIVE: To evaluate the relationship between serum levels of soluble Fas(sFas), soluble Fas li gand(sFasL), soluble IL-2 receptor(sIL-2R) and coronary heart disease (CHD). METHODS: With enzyme-linked immunosorbent assay (ELISA) tests, sFas, sFasL and sIL-2R were measured in the sera from 30 patients with CHD and 26 subjects without CHD as controls. RESTULTS: Mean level of sFas was significantly higher in patients with CHD than in controls [(1 583.41+/-174.46)ng/L compared with (1 374.55+/-142.42)ng/L, P<0.01]. Compared with the controls, the mean level of sIL-2R was significantly higher in patients with CHD [(944.50+/-395.59)ng/L compared with (652.45+/-163.36)ng/L P<0.01]. Moreover, in patients with CHD sFas and sIL-2R were positively correlated (r=0.418 P<0.05). Whereas no such difference was found between both groups in sFasL (P<0.05). CONCLUSION: High levels of serum sFas and sIL-2R were associated with CHD, and elevation of sFas may inhibit apoptosis in activated T cells, leading to coronary events.

[Effects of carvedilol on circulating levels of endothelin and von Willebrand factor in patients with unstable angina pectoris]

OBJECTIVE: To observe the effect of carvedilol on circulating levels of endothelin (ET) and von Willebrand factor (vWF) in patients with unstable angina pectoris (UAP). METHODS Forty patients with UAP were randomly divided into two groups. On the basis of anti coagulated and vasodilator remedy patients in control group(n=21) were given benazeptil(10 mg/d) for three days while patients in therapeutic group(n=19) were administered carvedilol(40 mg/d) for three days. Before and at the end of treatment,ET was measured by RIA and vWF by ELISA in patients with UAP and healthy individuals(n=20), heart rate and blood pressure were also recorded. RESTULTS The levels of circulating ET 101.8+/-28.9 versus 110.6+/-43.5 ng/L and vWF 162.6+/-55.6 versus 172.9+/-37.8 % between control group and carvedilol group were not significantly different before treatment, but both were higher than those in healthy individual ET 81.2+/-34.0 ng/L, vWF 142.0+/-49.4 % (P<0.05). After the treatment, the levels of ET 106.3+/-38.2 ng/L and vWF 155.4+/-54.2 % in control group did not decrease significantly (P>0.05), while those in carvedilol group ET 89.2+/-45.5 ng/L, vWF 129.2+/-48.8 % decreased markedly with the reduction of heart rate and blood pressure(P<0.05). CONCLUSION Carvedilol can decrease circulating levels of endothelin and von willebrand factor in patients with UAP markedly.

Subthreshold membrane potential oscillations of type A neurons in injured DRG

An abundance of subthreshold membrane potential oscillations (SMPOs) at resting potential was observed in the neurons of chronically compressed dorsal root ganglia (DRG) using intracellular recording in vivo. Out of 386 neurons, 63 type A neurons displayed SMPOs. Three types of SMPOs were distinguished based on their characterizations of oscillation: (1) A regular pattern of SMPO emerged consistently with a mean frequency of 86 Hz and mean amplitudes of 3.3 mV. (2) A spindle-like pattern of SMPO was denominated by a spindle alteration of its amplitude. (3) An irregular pattern of SMPO had no rule on its change of amplitude and frequency. Compared with normal DRG neurons and injured DRG neurons but without SMPO, the injured DRG neurons with SMPO had the lowest spike rheobase, in accordance with the detection of spike accommodation. No significant differences among the three groups can be found in either membrane potential or input resistance. Further observation showed that the spontaneous discharge of hyperexcitable neurons usually occurred on the depolarizing phase of oscillations. In addition, the regular pattern of SMPO was based on the period and integer multiple patterns of spontaneous discharges. The spindle-like pattern of SMPO contributed to spontaneous bursting discharge. The irregular pattern of SMPO had a striking relation with irregular spontaneous discharge. The results show that neurons with SMPO in injured DRG have a higher excitability than those without SMPO, and that the SMPO underlie the patterns of spontaneous discharges, suggesting that SMPO is the basic electrophysiological change of hyperexcitable neurons.

Subthreshold membrane oscillations underlying integer multiples firing from injured sensory neurons

Integer multiples firing (IMF), a special temporal pattern of firing, was recently observed in spontaneous discharge from injured dorsal root ganglion (DRG) neurons. To investigate the mechanism underlying IMF, the injured DRG neurons of rat were recorded intracellulary. Of 64 recorded A-neurons discharging spontaneously, eight fired spikes in the IMF pattern. Interspike interval (ISI) time series of IMF showed a structure of distinct bands on scatter map. Regular subthreshold membrane oscillations (SMOs) with relatively stable amplitude and frequency were observed on all eight IMF neurons. IMF could be induced from the neurons in periodic firing by local application of tetrodotoxin (TTX), a Na+ channel antagonist. During this process, the amplitude of SMOs varied markedly. Some SMOs were below action potential threshold so that they did not trigger spikes. Nor did some SMOs, though their amplitude were obviously beyond the threshold measured from nearby spikes. The results indicate that regular SMOs existent in injured DRG A-neurons underlie IMF, and the TTX-induced transformation of firing pattern from periodic to integer multiples may occur in two ways: decreasing the amplitude of SMOs and/or elevating action potential threshold.

[Sympathetic-sensory coupling in neuropathic pains]

Peripheral tissue and nerve injury lead to chronic pain symptoms, including spontaneous pain, allodynia and hyperalgesia. Sympathetic nervous system involves in pathological changes above, either through development of abnormal sympathetic function or through its effects on abnormally functioning afferent nerves, thereby to cause many neuropathic pains. This review focuses on the progress at present of sympathetic-sensory coupling and its receptors, intracellular and neural mechanisms.

Adrenergic sensitivity of neurons with non-periodic firing activity in rat injured dorsal root ganglion

In this study, we compared the sensitivity of non-periodically and periodically active neurons in chronically compressed dorsal root ganglion in rats to norepinephrine and sympathetic stimulation. Forty-nine of 58 (84.5%) neurons with non-periodic activity showed responses to norepinephrine, whereas only five of 48 (10.4%) neurons with periodic activity displayed any response. The dose-response relationship of norepinephrine to the irregular burst pattern neurons shifted towards the left significantly compared to that of the periodic activity neurons. Responses to norepinephrine became apparent in eight neurons after their periodic firing activity was transformed into the non-periodic firing activity through the increase in Ca(2+). Changes in the time-response curves indicate a higher sensitivity of irregular burst pattern neurons to sympathetic stimulation than the periodic activity neurons. Finally, deterministic dynamics contained within the interburst interval series for non-periodic activity were identified. From these results, we suggest that the non-periodic activity neurons have a higher adrenergic sensitivity than those displaying periodic activity, and that this sensitivity may depend on the deterministic chaos within its firing dynamic system.

[Relationship between the sensitivity to tetraethylammonium and firing patterns of injured dorsal root ganglion neurons]

In order to study the relationship between the firing patterns of injured dorsal root ganglion (DRG) neurons of rat and their sensitivity to tetraethylammonium (TEA), spontaneous activities from single fibers of chronically compressed DRG neurons were recorded. Two patterns of spontaneous activity were found: periodic pattern and non-periodic pattern. These two types of neurons showed different sensitivity to TEA with 27.3% in periodic and 93.2% in non-periodic firing neurons responding to TEA (2 mmol/L) (P<0.01). The responses to TEA of different concentrations were greater in the non-periodic firing neurons than in the periodic firing ones (P<0.01). The responses to TEA became apparent in 5 neurons after their periodic firing pattern was transformed into non-periodic firing pattern through an increase in Ca(2+). The non-periodic interburst interval of the bursting discharge decreased significantly while the periodic burst interspike interval had no response to TEA. The unstable period orbits were found in bursting discharge, indicating deterministic chaos during bursting discharge. It is concluded that non-periodic firing neurons with chaos are more sensitive to TEA than periodic firing neurons.

Detection of determinism within time series of irregular burst firing from the injured sensory neuron

Irregular burst firing is spontaneously generated by rat dorsal root ganglion neuron after chronic compression. To investigate the time series of burst firing, we recorded interspike intervals (ISIs) of single-unit firing in vitro and processed the ISIs to obtain interevent intervals (IEIs). Then, two non-linear methods were applied to detect deterministic dynamic behaviors in IEI series. No evidence for the existence of determinism was found with non-linear prediction method. Using unstable periodic orbit identification method, significant period-1 orbits were identified in all 10 data, period-2 orbits in eight, and period-3 orbits in six. The results indicate that there exist significant deterministic behaviors in the time series of irregular burst firing from the injured sensory neuron.