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Wen-Jun Yuan

Publications and source records attributed to Wen-Jun Yuan.

At least 19 recordsLinked to original sources
PubMed2006

Cardiovascular effects of centrally applied endothelin-1 1-31 and its relationship to endothelin-1 1-21 in rats.

Endothelin-1(1-31) (ET-1(1-31)) is a novel member of the endothelin family, which comprises 31 amino acids and derived from the selective hydrolysis of big ET-1 by chymase. Although ET-1(1-31) has been reported to be involved in biological effects via direct or indirect (converting to ET-1(1-21)) mechanisms, the cardiovascular effects of central ET-1(1-31) are not fully identified. The present study was designed to comparatively investigate the cardiovascular effects of intracerebroventricular (icv) application of ET-1(1-31) or ET-1(1-21) in anesthetized rats. Injection (icv) of ET-1(1-31) (500 pmol) produced a biphasic blood pressure response: an initial increase (from 118+/-8 to 138+/-14 mmHg, P<0.05) followed by a sustained decrease in BP (from 118+/-8 to 58+/-9 mmHg, P<0.05), which was very similar to BP response to icv injection of big ET-1 (500 pmol) or ET-1(1-21) (25 pmol)(.) The cardiovascular effects of icv injection of ET-1(1-31) or ET-1(1-21) were completely antagonized by ET(A) receptor antagonist BQ123 but not ET(B) receptor antagonist BQ788. Furthermore, pretreatment with ET converting enzyme inhibitor phosphoramidon (10 nmol) abolished the cardiovascular effects evoked by icv injection of ET-1(1-31) or big ET-1. In conclusion, the current data showed that central ET-1(1-31) produced the similar cardiovascular effects as those of central ET-1(1-21), and suggesting that the central cardiovascular effects of ET-1(1-31) resulted from it converting to ET-1(1-21) and then activating ET(A) receptors.

Animals↗
PubMed2006

Arrhythmogenic action of endothelin-1(1-31) through conversion to endothelin-1(1-21).

Endothelin (ET)-1(1-21) is known to play an important role in the pathogenesis of acute ischemic arrhythmia. In the present study, we attempted to determine whether administration of ET-1(1-31) would result in arrhythmia in perfused isolated rat hearts. Forty-eight Sprague-Dawley rats weighing approximately 250-350 g were randomized into 6 groups. Heart was isolated and perfused in a Langendorff mode. The effects of ET-1(1-31) on arrhythmia, heart rate, coronary flow, and heart function were analyzed. Perfusion with 1 nM ET-1(1-31) resulted in frequent ventricular ectopic beats (VEBs) and ventricular tachycardia (VT). Overall VEB was 128.0 (approximately 66.0-1015.0), and the arrhythmia score (AS) was 2.18 +/- 0.87; both were significantly higher than those of the control group (P < 0.01). Pretreatment with perfusion of 10 nM of the ETA-receptor antagonist BQ(123) markedly attenuated the occurrence of VEB and VT induced by ET-1(1-31). AS in 10 nM BQ123 group was significantly lower than that in 1 nM ET-1(1-31) group (P < 0.01). The arrhythmia induced by 1 nM ET-1(1-31) was partially but significantly reduced by phosphoramidon (1 microM), a neutral endopeptidase/ET-converting enzyme inhibitor. ET-1(1-31) per se caused arrhythmia in perfused isolated rat hearts. This arrhythmogenic action is in part mediated by ET(A) receptor and may be attributed mainly to the conversion of ET-1(1-31) to ET-1(1-21.).

Animals↗
PubMed2005

Role of dual-site phospholamban phosphorylation in intermittent hypoxia-induced cardioprotection against ischemia-reperfusion injury.

Cardioprotection by intermittent high-altitude (IHA) hypoxia against ischemia-reperfusion (I/R) injury is associated with Ca(2+) overload reduction. Phospholamban (PLB) phosphorylation relieves cardiac sarcoplasmic reticulum (SR) Ca(2+)-pump ATPase, a critical regulator in intracellular Ca(2+) cycling, from inhibition. To test the hypothesis that IHA hypoxia increases PLB phosphorylation and that such an effect plays a role in cardioprotection, we compared the time-dependent changes in the PLB phosphorylation at Ser(16) (PKA site) and Thr(17) (CaMKII site) in perfused normoxic rat hearts with those in IHA hypoxic rat hearts submitted to 30-min ischemia (I30) followed by 30-min reperfusion (R30). IHA hypoxia improved postischemic contractile recovery, reduced the maximum extent of ischemic contracture, and attenuated I/R-induced depression in Ca(2+)-pump ATPase activity. Although the PLB protein levels remained constant during I/R in both groups, Ser(16) phosphorylation increased at I30 and 1 min of reperfusion (R1) but decreased at R30 in normoxic hearts. IHA hypoxia upregulated the increase further at I30 and R1. Thr(17) phosphorylation decreased at I30, R1, and R30 in normoxic hearts, but IHA hypoxia attenuated the depression at R1 and R30. Moreover, PKA inhibitor H89 abolished IHA hypoxia-induced increase in Ser(16) phosphorylation, Ca(2+)-pump ATPase activity, and the recovery of cardiac performance after ischemia. CaMKII inhibitor KN-93 also abolished the beneficial effects of IHA hypoxia on Thr(17) phosphorylation, Ca(2+)-pump ATPase activity, and the postischemic contractile recovery. These findings indicate that IHA hypoxia mitigates I/R-induced depression in SR Ca(2+)-pump ATPase activity by upregulating dual-site PLB phosphorylation, which may consequently contribute to IHA hypoxia-induced cardioprotection against I/R injury.

Altitude↗
PubMed2005

Blood pressure responses of endothelin-1 1-31 within the rostral ventrolateral medulla through conversion to endothelin-1 1-21.

Endothelin-1 1-31 (ET-1 1-31), a novel member of the endothelin family comprising 31 amino acids and derived from the selective hydrolysis of big ET-1 by chymase, directly activates endothelin receptors or converts to ET-1 1-21 by ET converting enzyme (ECE). The cardiovascular effects of central ET-1 1-31 are not identified. The present study was designed to investigate the cardiovascular actions of ET-1 1-31 within the rostral ventrolateral medulla (RVLM) in anesthetized rats. Bilateral injection of ET-1 1-31 (0.5, 1, and 2 pmol for each side) into the rostral ventrolateral medulla produced an initial pressor and/or a long-lasting hypotensive action but did not affect HR. Unilateral microinjection of 2 and 4 pmol of ET-1 1-31 into the rostral ventrolateral medulla only produced a significant (P < 0.05) transient increase in blood pressure by an average of 13 and 12 mm Hg, respectively, whereas unilateral microinjection of 8 pmol of ET-1 1-31 produced a sustained fall in blood pressure (from 92 +/- 6 to 69 +/- 8 mm Hg, P < 0.05). The transient pressor effect of unilaterally injecting ET-1 1-31 (4 pmol) into the rostral ventrolateral medulla was completely abolished by pretreatment with either ETA receptor antagonist BQ123 (83 +/- 2 versus 84 +/- 5 mm Hg, P > 0.05) or ET converting enzyme inhibitor phosphoramidon (99 +/- 5 versus 99 +/- 7 mm Hg, P > 0.05) but not ETB receptor antagonist IRL1038 (89 +/- 6 versus 96 +/- 7 mm Hg, P < 0.05). In addition, prior injection of phosphoramidon also completely abolished the long-lasting hypotension of intra-RVLM ET-1 1-31 (8 pmol) but did not modify the depressor action of intra-RVLM ET-1 1-21 (from 100 +/- 6 to 76 +/- 8 mm Hg, P < 0.05). In conclusion, the current results suggest that the cardiovascular effects of intra-RVLM ET-1 1-31 might be the result of conversion of ET-1 1-31 to ET-1 1-21 through activation of ETA receptors.

Animals↗
PubMed2005

Phosphorylated heat shock protein 27 is involved in enhanced heart tolerance to ischemia in short-term type 1 diabetic rats.

AIM: To examine the tolerance of type 1 diabetic hearts to ischemia and reperfusion injury. Myocardial contents of 27-kDa and 70-kDa heat shock proteins (hsp) as well as phosphorylated hsp27 were also determined. METHODS: Hearts from hyperglycemic rats 3 weeks after streptozocin injection and age-matched normal rats were subjected to ischemia and reperfusion in vitro. Cardiac function and electrocardiogram were recorded throughout experiments. Myocardial heat shock proteins were detected with Western blot. RESULTS: Despite depressed systolic function at the baseline, diabetic hearts exhibited considerable enhancement in post-ischemic heart function, manifested by an increase in the maximal rate of left ventricular pressure rise and fall (post-ischemic dp/dtmax and dp/dtmin were 560+/-117 and -313+/-68 mmHg/s in control, n=7, 1249+/-57 and -1204+/-36 mmHg/s in diabetes, n=10, P<0.01). Reperfusion ventricular fibrillation in the diabetic group were attenuated compared with controls (1.5+/-0.3 vs 7.2+/-2.1 min in control, P<0.01). The increased heart resistance to ischemia in diabetes was associated with hyperglycemia and accompanied by enhanced expression of myocardial phosphorylated hsp27 with normal aortic vessel relaxation. Cardioprotection was abrogated by metabolic correction with insulin and accompanied by phospho-hsp27 reduction. CONCLUSION: Heart resistance to ischemia is increased in type 1 diabetes, and hyperglycemia may present a mild yet stressful stimulus leading to upregulation of endogenous stress protein, which may play a potential role in cardioprotection and compensate for detrimental effects of hyperglycemia in diabetes.

Animals↗
PubMed2005

[Endothelin signaling in cardiac myocyte].

Endothelin can affect the contractile properties of cardiacmyocyte, stimulate myocyte growth and myofibrillogenesis, and increase resistance to apoptosis by intracellular signaling pathways. This article briefly reviews the regulative effects of these signaling pathways including protein kinase C, mitogen activated protein kinase, and phosphoinositide 3'-OH kinase/protein kinase B.

Animals↗
PubMed2004

Electrophysiological evidences for the contribution of NMDA receptors to the inhibition of clonidine on the RVLM presympathetic neurons.

The main objective of this study is to test the hypothesis that N-methyl-D-aspartate (NMDA) receptors within the rostral ventrolateral medulla (RVLM) are involved in the inhibition of clonidine on the RVLM presympathetic neurons. Totally, 22 presympathetic neurons were recorded in anesthetized and paralyzed rats. The majority of these neurons (n=16 of 22) were significantly inhibited by iontophoretic (30 nA) clonidine, the other 6 neurons were insensitive to clonidine. In seven clonidine-sensitive neurons, iontophoretic clonidine (30 nA) antagonized the neuronal excitation of iontophoretic NMDA receptor agonist NMDA (20 nA). In remaining nine clonidine-sensitive neurons, iontophoretic NMDA receptor antagonist MK801 (60 nA) significantly attenuated the neuronal inhibition of iontophoretic (30 nA) clonidine. In conclusion, these results suggest that NMDA receptors contribute to the inhibition of clonidine on the RVLM presympathetic neurons.

Action Potentials↗
PubMed2004

Interaction between clonidine and N-methyl-D-aspartate receptors in the caudal ventrolateral medulla of rats.

It is known that the caudal ventrolateral medulla (CVLM) plays an important role in controlling blood pressure and mediating the cardiovascular effects of centrally acting antihypertensive drugs such as clonidine. Recently, the effect of clonidine was believed to be related to the functional states of N-methyl-D-aspartate (NMDA) receptors. The present work was designed to observe the interactions between clonidine and NMDA receptor in the CVLM. Unilaterally injected clonidine (6 nmol) into the CVLM not only produced a pressor action, but also effectively (P<0.01, n=8) antagonized the decreases in both mean arterial pressure (MAP) (-22.3+/-5.0 to -7.9+/-2.3 mmHg) and heart rate (HR) (-31.9+/-5.9 to -10.3+/-2.7 beats/min) evoked by L-glutamate in the CVLM. Unilaterally injected NMDA receptor antagonist MK801 (200 pmol) into the CVLM significantly increased MAP by 26.5+/-3.7 mmHg and HR by 37.1+/-7.6 beats/min, and completely (P<0.01, n=10) abolished the pressor effect (16.1+/-6.6 to 1.5+/-2.8 mmHg) of clonidine in the CVLM. In conclusion, these findings show that NMDA receptors within the CVLM contribute to clonidine-induced action, and suggest that the CVLM plays an important role in the interaction between clonidine and NMDA receptors.

Animals↗
PubMed2004

Urotensin-II activates L-arginine/nitric oxide pathway in isolated rat aortic adventitia.

Urotensin-II (U-II), a cyclic peptide widely expressed in blood vessels, has diverse vascular actions that range from potent vasoconstriction to vasodilation. Although, U-II-induced vasodilation has been shown to be partially dependent on nitric oxide (NO), the involvement of vascular adventitia-derived NO, remains unknown. The present study aimed to elucidate the activation of U-II on L-arginine/NO pathway in isolated rat aortic adventitia. In adventitia of thoracic and abdominal aortas, the l-arginine/NO pathway was similarly characterized: the uptake of l-[(3)H]arginine was Na(+)-independent, with the peak occurring over around 40 min incubation; the total NO synthase (NOS) activity was mostly calcium-independent (>90%), and significantly inhibited by a specific iNOS inhibitor AMT; the production of NO metabolites nitrate and nitrite (NO(x)) was stimulated by L-arginine but not by D-arginine. In aortic adventitia exposed to rat U-II (10(-9) and 10(-8)M) for 6 h, the V(max) of l-[(3)H]arginine uptake over 40 min incubation was significantly increased, while the K(m) of l-[(3)H]arginine uptake showed no significant change. Besides, the iNOS mRNA level was up-regulated, the total NOS activity, largely calcium-independent, was significantly induced, and the NO(x) production was significantly stimulated by U-II. According to the same protocol as U-II, the positive control lipopolysaccharide (LPS, 10 microg/ml), which had been established to activate adventitial L-arginine/NO pathway, increased l-[(3)H]arginine uptake, iNOS activity and NO(x) production to a greater extent than U-II. In addition, the total NOS activities induced by 3 and 6h incubation of U-II and LPS were significantly inhibited by a specific inhibitor of protein synthesis, actinomycin D. In conclusion, the results showed that rat U-II activated L-arginine/NOS/NO pathway in rat aortic adventitia, suggesting a potential contributive role of adventitia-derived NO in the vasodilator response of U-II.

Animals↗
PubMed2004

HSP70 and GRP78 induced by endothelin-1 pretreatment enhance tolerance to hypoxia in cultured neonatal rat cardiomyocytes.

The heat shock protein 70 and glucose-regulated protein 78 have been shown to protect cells against deleterious stimuli. This study was performed to determine whether endothelin-1 pretreatment could increase cardiomyocyte tolerance to hypoxia and induce heat shock protein 70 and glucose-regulated protein 78 expression. Cultured cardiomyocytes were treated with endothelin-1 at doses of 0.01, 0.1 and 1.0 nmol/L for 10 minutes followed by 10 minutes endothelin-1-free normal medium prior to 12 hours hypoxia. Lactate dehydrogenase activity and malondialdehyde level in the medium were determined at the end of hypoxia, and myocyte heat shock protein 70 and glucose-regulated protein 78 were assayed with Western blot. Lactate dehydrogenase activity and malondialdehyde content in the medium were significantly elevated after hypoxia (P < 0.01, n = 6). Heat shock protein 70 and glucoseregulated protein 78 expression in cardiomyocytes also increased significantly after hypoxia (P < 0.01 vs control, n = 3). Endothelin- 1 pretreatment reduced lactate dehydrogenase and malondialdehyde after hypoxia, and increased heat shock protein 70 and glucoseregulated protein 78 levels during normal culture and hypoxia. Glucose-regulated protein 78 antisense oligodeoxynucleotide partially abrogated the protective effect of endothelin-1 pretreatment on hypoxic cardiomyocyte injury. This study indicated that endothelin-1 pretreatment could protect hypoxic cardiomyocytes and might exert this effect through upregulation of heat shock protein 70 and glucose-regulated protein 78.

Animals↗
PubMed2003

Blockade of N-methyl-D-aspartate receptors within the rostral ventrolateral medulla antagonizes clonidine-induced cardiovascular effects.

There is wide agreement that the rostral ventrolateral medulla (RVLM) plays a crucial role in the regulation of blood pressure (BP), and that there may be a close correlation between the actions of centrally acting antihypertensive agents and N-methyl-D-aspartate (NMDA) receptor functional states. The present study was done to test the hypothesis that NMDA receptors within the RVLM were involved in the cardiovascular effects of centrally acting antihypertensive drug clonidine in anesthetized and paralyzed rats. Prior unilateral microinjection of NMDA receptor antagonist dizocilpine (MK801, 500 pmol) into the RVLM significantly attenuated (p<0.01, n=9) the reductions of BP (-24+/-6 to -8+/-4 mm Hg) and heart rate (-49+/-9 to -14+/-7 bpm) induced by unilaterally injected clonidine (5 nmol) into the RVLM. Prior bilateral microinjection of MK801 (500 pmol for each side) into the RVLM effectively (p<0.01, n=7) antagonized the hypotension (-25+/-5 to -8+/-2 mm Hg) and bradycardia (-43+/-7 to -11+/-4 bpm) of intravenously administered clonidine (10 microg kg(-1)). Importantly, iontophoretic application of MK801 (60 nA) significantly (p<0.01, n=9) prevented the inhibitory effect of intravenously (10 microg kg(-1)) injected clonidine on the discharge of presympathetic neurons in the RVLM (neuronal inhibition: -39+/-6 to -10+/-2%). In conclusion, the present study shows that the RVLM administrated MK801 effectively antagonizes clonidine-induced cardiovascular effects, and suggests that NMDA receptors within the RVLM contribute to clonidine actions.

Adrenergic alpha-Agonists↗
PubMed2003

[Effects of urotensin II on isolated rat hearts under normal perfusion and ischemia reperfusion].

To shed light on cardiac effects of the potent vasoconstrictive peptide urotensin II (U II), Langendorff-perfused isolated rat hearts were consecutively perfused with 0.1, 1 and 10 nmol/L U II, for 5 min at each dose, followed by 5-min washout. Moreover, isolated hearts subjected to 20-min global no-flow ischemia were reperfused with U II (1 or 10 nmol/L) for 20 min. Heart function parameters including heart rate, left ventricular pressure and dP/dt were monitored; content of protein and myoglobin, and activity of lactate dehydrogenase (LDH) in coronary effluent were determined; malondialdehyde (MDA) in myocardium and [(125)I]-U II binding sites in plasma membrane were measured after the completion of perfusion. The results showed that: (1) In normal rat hearts, the coronary flow was decreased and the heart function was suppressed by U II dose-dependently, and these changes were not abolished by washout. The leakage of cardiac protein, myoglobin and LDH increased with the increment of U II, but it diminished rapidly after washout. In contrast, MDA content in U II -treated myocardium was not statistically different from that in normal myocardium. (2) Ischemia-reperfusion caused significant decreases in coronary flow, suppression of heart function, and leakage of protein and LDH. In U II -reperfused hearts, all these disorders were significantly aggravated and myocardial MDA content significantly increased (P<0.01), to a greater extent in the presence of higher dose of U II. (3) The maximal binding capacity (B(max)) of U II receptors in plasma membrane from ischemia-reperfusion myocardium increased significantly as compared with that of normal myocardium (20.53+/-1.98 vs 14.65+/-1.78 fmol/mg pr, P<0.01), while Kd remained unchanged. These results indicate that U II caused injury to the isolated rat hearts under normal perfusion, and worsened the injury of the hearts under ischemia-reperfusion, in which U II receptors were up-regulated.

Animals↗
PubMed2003

Preserved postischemic heart function in sucrose-fed type 2 diabetic OLETF rats.

Cardiovascular disease is one of the most important causes of morbidity and mortality in diabetes mellitus, but there has been controversy over functional impairment of diabetic hearts and their tolerance to ischemia. We studied ischemic heart function in type 2 diabetic rats with different degrees of hyperglycemia and its relationship with cardiac norepinephrine release. Otsuka Long-Evans Tokushima Fatty rats (OLETF) and age-matched Long-Evans Tokushima Otsuka normal rats (LETO) were used. One group of OLETF rats was given 30% sucrose in drinking water (OLETF-S). Hearts were isolated and perfused in a working heart preparation and subjected to 30 min ischemia followed by 40 min reperfusion at age of 12 months. Hemodynamics and coronary norepinephrine overflow were examined. Fasting plasma glucose in OLETF increased markedly at 12 months and sucrose administration exacerbated hyperglycemia in diabetic rats (LETO 6.6 +/- 0.5, OLETF 8.3 +/- 0.7, OLETF-S 15.0 +/- 1.7 mmol/L, P < 0.01). Basic cardiac output in OLETF was decreased as compared with LETO and OLETF-S (LETO 29.4 +/- 2.5, OLETF 24.0 +/- 2.4, OLETF-S 27.0 +/- 0.9 ml/min/g, P < 0.05) and remained very low after ischemia, while in OLETF-S it was well preserved (OLETF 4.2 +/- 2.1, OLETF-S 13.7 +/- 2.6 ml/min/g, P < 0.01). Correspondently, cardiac norepinephrine released during ischemia and reperfusion was lower in OLETF-S (OLETF 2.3 +/- 1.0, OLETF-S 0.7 +/- 0.1 pmol/ml, P < 0.01). Thus, OLETF hearts were more vulnerable to ischemia but sucrose feeding rendered their hearts resistant to ischemia. Less norepinephrine release may play a role in preventing postischemic functional deterioration in sucrose-fed diabetic hearts.

Aging↗
PubMed2003

[Preventive effect of endothelin-1 pretreatment on hypoxia-induced injury in cultured neonatal rat cardiomyocytes].

This study was designed to observe the effects of endothelin-1 (ET-1) pretreatment on hypoxia-induced injury and changes in [Ca(2+)](i) in cultured neonatal rat cardiomyocytes. The activity of lactate dehydrogenase (LDH) and superoxide dismutase (SOD), and the content of malondialdehyde (MDA) in the supernatant were determined in the cultured cardiomyocytes subjected to a 12-h hypoxia induced by a 3% O(2)-5% CO(2) atmosphere at 37 with or without ET-1 pretreatment. [Ca(2+)](i) was measured with Ca(2+)-sensitive fluorescent probe fluo-3/AM under a laser scanning confocal microscope. Fluorescence intensity emitted from fluo-3/AM-loaded cells reflected the concentration of [Ca(2+)](i). The hypoxia model used in [Ca(2+)](i) measurement was established by continously perfusing cardiomyocytes for 30 min with 95% N(2)-5% CO(2) saturated DMEM solution containing 1 mmol/L Na(2)S(2)O(4). Pretreatment with ET-1 consisted of three cycles of ET-1 perfusion (5 min for each) followed by ET-1-free DMEM solution (10 min for each) prior to hypoxia. The results showed that (1) after incubation in a 3% O(2)-5% CO(2) hypoxic atmosphere for 12 h, the activity of LDH and the content of MDA in the supernatant significantly increased from 19.33+/-1.03 U/L to 43.33+/-1.21 U/L and from 0.91+/-0.03 nmol/L to 1.71+/-0.02 nmol/L, respectively, whereas the activity of SOD decreased from 33.48+/-1.15 U/ml to 16.93+/-1.11 U/ml (P<0.01). In hypoxic cardiomyocytes pretreated with 0.01-1 nmol/L ET-1, LDH release and supernatant MDA content were decreased, while SOD activity was enhanced dose-dependently (P<0.01). (2) The spontaneous calcium transient in cultured cardiomyocytes terminated at 29+/-1.5 s and [Ca(2+)](i) increased by 107+/-13.2% during perfusion of hypoxic solution (P<0.001) at the end of 30 min. ET-1 (0.01-1 nmol/L) increased the frequency of [Ca(2+)](i) transient in cultured cardiomyocytes in a dose-dependent manner (P<0.01). The termination of [Ca(2+)](i) transient and the elevation of [Ca(2+)](i) caused by hypoxia were postponed by pretreatment with 0.01-1 nmol/L ET-1 (P<0.01). These results show that pretreatment with 0.01-1 nmol/L ET-1 attenuates hypoxia-induced injury and [Ca(2+)](i) changes in cultured neonatal cardiomyocytes, indicating a cyto-protective role of ET-1 pretreatment.

Animals↗
PubMed2003

Involvement of I(1)-imidazoline receptors in baroreceptor reflex in the caudal ventrolateral medulla of rats.

There is ample evidence to show the existence of center I(1)-imidazoline receptors that are involved in the regulation of cardiovascular activities. The purpose of this study was to examine the possible role of I(1)-imidazoline receptors and alpha(2)-adrenoceptors within the caudal ventrolateral medulla (CVLM) in mediating the baroreceptor reflex in anesthetized rats. Unilateral microinjection of idazoxan (2 nmol in 50 nl), a mixed antagonist of I(1)-imidazoline receptors and alpha(2)-adrenoceptors, into the CVLM significantly (P<0.01) decreased blood pressure (BP), heart rate (HR), and the firing rate of presympathetic neurons in the rostral ventrolateral medulla (RVLM) by 21+/-6 mmHg, 25+/-5 beats per min and 3.5+/-0.9 spikes/s, respectively. Moreover, unilateral injection of idazoxan into the CVLM significantly (P<0.01) reduced the inhibitory responses of the ipsilateral RVLM presympathetic neurons evoked by stimulation of aortic nerve and elevation of BP, and partially inhibited the neuronal cardiac cycle-related rhythm. Depressor responses evoked by aortic nerve stimulation were significantly (P<0.01) attenuated 10 and 20 min after bilateral microinjection of idazoxan (2 nmol in 50 nl for each side) into the CVLM (-20+/-4 and -30+/-4 vs. -40+/-1 mmHg). However, injection of yohimbine (500 pmol in 50 nl), a selective alpha(2)-adrenoceptor antagonist, into the CVLM did not affect the resting cardiovascular activities and baroreceptor reflex. It is concluded that the CVLM I(1)-imidazoline receptors are involved in maintenance of tonic cardiovascular activities and transmission of the baroreceptor reflex.

Action Potentials↗
PubMed2003

Comparative study of sinoaortic denervated rats and spontaneously hypertensive rats.

BACKGROUND: Both hypertension and high blood pressure variability (BPV) are involved in cardiovascular damage. This comparative study was designed to explore the possible effects of both of these phenomena on the cardiovascular system. METHODS: The high BPV model of 16-week sinoaortic denervated (SAD) rats and the hypertension model of spontaneously hypertensive rats (SHR) were used for comparison at the same age of 26 weeks. The comparison was focus on hemodynamics, cardiovascular hypertrophy, and hemodynamic responses to ketanserin. Linear regression analysis was performed to study the role of hemodynamics in cardiovascular hypertrophy. RESULTS: In SHR, hypertension was accompanied by a moderately high BPV, whereas in SAD rats, substantially high BPV existed alone, without hypertension. Left ventricular hypertrophy was severe in SHR but was mild in SAD rats. Aortic hypertrophy was present in SAD rats but was absent in SHR. In SAD rats, the hypertrophy was correlated with BPV but not with blood pressure (BP) level. However, in SHR, hypertrophy was correlated with both BP and BPV level. The BP-lowering effect of ketanserin was comparable in both models, whereas its BPV-lowering effect was greater in SAD rats than in SHR. This hypersensitivity was associated with basal BPV level in SAD rats. CONCLUSIONS: These results indicate that hypertension may be more important than high BPV in causing left ventricular hypertrophy, and that the aorta may be more sensitive to substantially high BPV.

Animals↗
PubMed2003

Inflammation is involved in the organ damage induced by sinoaortic denervation in rats.

OBJECTIVE: The present study was designed to test the hypothesis that inflammation is involved in the end-organ damage (EOD) induced by sinoaortic denervation (SAD) in rats. METHOD: SAD was performed in male Sprague-Dawley rats at the age of 10 weeks. Under anaesthesia, aortic nerves were cut and the sinus region of the carotid artery was stripped and painted with 10% phenol. Pathological evaluation of EOD and the determination of plasma or tissue levels of the factors related to inflammation, including thromboxane B2 (TXB2) interleukin-1 (IL-1), tumour necrosis factor alpha (TNF-alpha) and reactive oxygen species (ROS) were performed at 16 weeks after SAD. Pathological evaluation of EOD included heart weight ratio, myocardial and blood vessel hydroxyproline and collagen volume fraction, glomerular injury score and number of infiltrating inflammatory cells. Indomethacin (20 mg/kg per day, orally) or vitamin E (100 mg/kg per day, orally) was administered for 12 weeks, beginning from 4 weeks after SAD, to observe their effects on SAD-induced EOD. RESULTS: There were significant fibrosis and inflammatory infiltration in the myocardium and blood vessels, represented by higher hydroxyproline and collagen volume fraction, and a large amount of inflammatory cells in the tissues of SAD rats. Heart weight and kidney glomerular injury score were significantly higher in SAD than in sham-operated rats. Plasma TXB2, TNF-alpha, IL-1 and tissue ROS increased significantly after SAD. Indomethacin and vitamin E significantly decreased the contents of some factors related to inflammation in SAD rats. Both drugs also alleviated myocardial and vessel fibrosis, inflammatory infiltration and kidney damage. CONCLUSION: Inflammation is involved in the organ damage induced by SAD in rats.

Animals↗