Apelin in the hypothalamic paraventricular nucleus improves cardiac function in surgical trauma rats.

Apelin is a novel endogenous active peptide. The aim of this study is to investigate whether apelin in the paraventricular nucleus (PVN) can improve the cardiac function in rats subjected to thoracic surgery trauma, and whether it is involved in the protective effect of electro-acupuncture (EA). Sprague-Dawley rats were randomly divided into non-stressed group (control), thoracic surgical trauma stressed group (trauma) and bilateral Neiguan EA applied on thoracic surgical trauma stressed group (trauma + EA-PC 6). The mRNA expressions of apelin receptor (APJR) and apelin in the PVN were detected by real time-PCR. The exogenous apelin-13 (6 mmol/L, 0.1 µL) was microinjected into the rat PVN in the thoracic trauma group, and the effects of apelin-13 on the blood pressure (BP), heart rate (HR) and the discharge of rostral ventrolateral medulla (RVLM) neurons were observed through the simultaneous recording technology by polygraph. The results showed that the APJR mRNA expression was significantly decreased in the rats of trauma group as compared with that in the control group (P < 0.05), and a decline trend of apelin mRNA expression was also observed. EA application at bilateral Neiguan acupoints partially recovered the decline of APJR and apelin mRNA expression by the treatment of thoracic trauma. Both mean arterial pressure and HR in the thoracic surgical trauma group were significantly increased by the microinjection of exogenous apelin-13 into the PVN (P < 0.05), and the single-unit discharge rate of RVLM neurons also had an increasing trend. These results suggest that apelin in the PVN can improve the cardiac function of thoracic surgical trauma rats, and may be involved in the protective effects of EA.

Nitric oxide modulates cardiovascular function in the rat by activating adenosine A2A receptors and inhibiting acetylcholine release in the rostral ventrolateral medulla.

1. Nitric oxide (NO), a gas transmitter, modulates many physiological processes, including the central regulation of cardiovascular activity. However, the mechanisms underlying the regulation of cardiovascular activity remain relatively unexplored. In the present study, we hypothesized that central NO-dependent sympathetic inhibition is mediated by activation of adenosine A(2A) receptors (A(2A)R) and inhibition of acetylcholine (ACh) release in the rostral ventrolateral medulla (RVLM). 2. L-Arginine (L-Arg; an NO donor; 100 nmol/100 nL) was microinjected into the RVLM of male Sprague-Dawley rats and heart rate variability (HRV) was assessed as an index of cardiac sympathovagal balance. Following microinjection of L-Arg, decreases were seen in mean arterial pressure (MAP), heart rate (HR) and the ratio of the low- to high-frequency components (LF/HF) of HRV. Pretreatment of rats with SCH58261 (40 pmol/60 nL into the RVLM), a competitive antagonist of the A(2A) R, attenuated these effects. 3. Western blot analysis and ELISA revealed that adenosine and A(2A)R levels increased in the RVLM following L-Arg microinjection, whereas ACh and muscarinic M(1) receptor levels decreased significantly, in parallel with the cardiovascular responses to L-Arg microinjection. The decrease in ACh levels was abolished by SCH58261 pretreatment. 4. Microinjection of N(G)-nitro-L-arginine methyl ester (a non-selective inhibitor of NO synthase; 15 nmol/100 nL) into the RVLM significantly increased MAP, HR and sympathetic activity, as evidenced by HRV (LF, HF and the LF/HF ratio were all increased). 5. The results indicate that the central NO/NO synthase system in the RVLM may modulate cardiovascular activity by activating the A(2A)R, which subsequently inhibits activation of the muscarinic M(1) receptor.

Treadmill pre-training suppresses the release of glutamate resulting from cerebral ischemia in rats.

This study was designed to investigate the neuroprotective effect of treadmill pre-training against the over-release of glutamate resulting from cerebral ischemia. Sprague-Dawley rats underwent 2 weeks of treadmill run-training before cerebral ischemia was performed by middle cerebral artery occlusion. The level of glutamate in brain extracellular fluid was detected before, during and after ischemia/reperfusion. The expression of metabotropic glutamate receptor-1 (mGluR1) mRNA in striatum was examined after ischemia for 80 min and reperfusion for 240 min. Neurological defect score and brain infarction volumes were measured. The treadmill pre-training significantly suppressed the release of glutamate, and reduced the expression of mGluR1 mRNA at 59% (P < 0.01) and 62% (P < 0.05), respectively, as compared with the ischemia group. The neurological defect score and infarction volume were significantly improved by 75% (P < 0.01) and 74% (P < 0.01), respectively, in the pre-training group, as compared to the ischemia group. Treadmill pre-training has a significant neuroprotective function against ischemia/reperfusion injury, by suppressing glutamate release resulting from cerebral ischemia, and this effect may be mediated by downregulation of mGluR1.

Orexin-A and respiration in a rat model of smoke-induced chronic obstructive pulmonary disease.

1. Orexins are neuropeptides synthesized in the hypothalamus that regulate many physiological functions, including energy homeostasis, stress responses, sleep/wake states etc. It is now emerging that orexins may also regulate breathing, but little is known as to how they do this, particularly in chronic obstructive pulmonary disease (COPD). In the present study, we used a rat model of cigarette smoke-induced COPD to investigate orexin-A expression in the hypothalamus and medulla and its effect on respiration. 2. Sprague-Dawley rats were exposed to cigarette smoke (1 h twice daily) for 12 weeks. Lung function and pathological changes associated with inflammation and emphysema were determined to confirm the validity of the COPD model. 3. Hypothalamic and medullary orexin-A levels, as determined by radioimmunoassay, were higher in smoke-exposed than control rats. Furthermore, the expression of prepro-orexin (PPO) mRNA in the hypothalamus and orexin OX(1) receptor mRNA in the medulla, as determined by real-time quantitative polymerase chain reaction, was higher in smoke-exposed than control rats. 4. The number of orexin-A-positive neurons in the hypothalamus and OX(1) and OX(2) receptor-positive neurons in the ventrolateral medulla was higher in smoke-exposed than control rats. 5. Microinjection of orexin-A (1 µmol/L, 0.1 µL) into the pre-Bötzinger complex enhanced phrenic nerve discharge to a greater extent in smoke-exposed compared with control rats (61% vs 36%, respectively). 6. The findings of the present study demonstrate that the increased respiratory activity in smoke-exposed rats is due to an increase in orexin-A as well as upregulation of orexin receptors in the ventrolateral medulla.

Adrenomedullin in the rostral ventrolateral medulla is involved in the regulation of cardiovascular component of defensive responses induced by electrical stimulation of dorsal periaquaductal gray of the midbrain.

In this study, we used techniques of in situ hybridization, immunohistochemistry, electric stimulation of the dorsal periaquaductal gray of the midbrain (dPAG) and microinjection to investigate the changes of preproadrenomedullin (ppADM) gene expression encoding adrenomedullin (ADM) and ADM-like immunoreactivity (ADM-IR) in the medulla oblongata, especially in the rostral ventrolateral medulla (rVLM) of the rats receiving foot-shock and noise stress for 5 d, and the potential role of ADM in cardiovascular component of defense response in the rVLM. The results showed that ppADM mRNA and ADM-IR were widely distributed throughout the medulla oblongata. Highly labeled neurons were found in the ventrolateral reticular nucleus and hypoglossal nucleus. Moderately labeled neurons were seen in the facial, ambiguus, lateral reticular, paragigantocellular reticular, and inferior olivary nuclei. Weak signal was present over neurons of nucleus of the solitary tract. The expression of ppADM mRNA and ADM-IR increased significantly after foot shock and noise stress for 5 d as compared with that in control group (P<0.01). On the other hand, stimulation of the right dPAG raised the artery pressure (AP) rapidly from (116.4+/-8.9) mmHg to (140.0+/-9.8) mmHg, and heart rate (HR) from (378.0+/-7.5) beats/min to (413.0+/-8.2) beats/min, respectively, in the normotensive rats. After unilaterally microinjection of hADM(22-52) (a specific antagonist of ADM receptor, 1 pmol) into the right rVLM of the normotensive rats for 10 min, the rats received the stimulation of the dPAG again. Then we found that the DeltaAP and DeltaHR were lowered significantly within 60 min compared with those without hADM(22-52) application (P<0.05). After unilaterally microinjection of 0.1 pmol rat ADM (rADM) into the rVLM, dPAG stimulation caused no significant changes in DeltaAP and DeltaHR. Our results that foot-shock and noise stress induced significant increases of ppADM mRNA and ADM-IR in the rVLM, and microinjection of ADM receptor antagonist hADM(22-52) into the rVLM partly blocked the cardiovascular component of stress-defensive response induced by stimulation of the dPAG, suggest that ADM in the rVLM might be an important neurotransmitter or neuroregulator in the regulation of cardiovascular function in the stress-related defensive response.

Effects of melatonin on blood pressure in stress-induced hypertension in rats.

Melatonin, acting through its receptors, is involved in numerous physiological processes, including blood pressure (BP) regulation. In present study, the effect of melatonin inhibition on stress-induced hypertension was investigated. The hypertensive model consisted of male Sprague-Dawley rats subjected to electrical foot-shock combined with noise. Microinjection of melatonin (0.1 and 1.0 mmol/L) into the anterior hypothalamic area (AHA) produced a fall in BP in nomortensive rats and stress-induced hypertensive rats (SIHR). Luzindole (10 mmol/L), a competitive antagonist of melatonin MT1 and MT2 receptors, almost completely abolished the depressor effect of melatonin, the MT2 receptor-specific antagonist 4-phenyl-2-propionamidotetralin (10 mmol/L) partially blocked (by approximately 60%) the depressor effect of melatonin, whereas the MT3 receptor-selective antagonist prazosin (10 mmol/L) failed to antagonize the effects of melatonin. Brain microdialysis was performed in the AHA and the rostral ventrolateral medulla (RVLM). Melatonin and amino acids in the dialysate samples collected were detected by high-performance liquid chromatography combined with fluorescence detection. The results indicated that melatonin concentrations in the AHA were reduced in SIHR. Microinjection of melatonin into the AHA decreased glutamate release and increased GABA and taurine release in the RVLM, which were paralleled by a decrease in arterial pressure. The mRNA expression of MT2 in the AHA of SIHR was higher than that in normotensive control rats, whereas there was no significant difference in MT1 mRNA expressin between the two groups. The results of the present study suggest that both a decrease of melatonin and an increase in the MT2 receptor in the AHA are involved in the manifestation of stress-induced hypertension. Both MT1 and MT2 receptors participated in the antihypertensive effect of melatonin in the AHA. The antihypertensive effect of melatonin was related to the decreases in the excitatory amino acid glutamate and increases in the inhibitory amino acids taurine and GABA in the RVLM.

Effects of N(omega)-nitro-L-arginine methyl ester and aminoguanidine on lipopolysaccharide-induced airway hyperresponsiveness in guinea pigs.

BACKGROUND: The down-regulation of constitutive nitric oxide synthase (cNOS) and up-regulation of inducible nitric oxide synthase (iNOS) are associated with the allergen-provocated airway hyperresponsiveness (AHR). This study aimed to determine whether their alteration also plays an important role in the AHR induced by lipopolysaccharide (LPS). METHODS: Hartley male guinea pigs, weighing between 250 g and 350 g, were injected with LPS at a dose of 1 mg/kg every 24 hours for three days. A non-selective NOS inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME), or a selective inducible NOS inhibitor, aminoguanidine (AG), were used thirty minutes before each injection of LPS. Airway reactions, nitric oxide (NO) production and inflammatory changes were detected 24 hours after the last dose of LPS. RESULTS: AG significantly decreased the NO production in the bronchoalveolar lavage fluid (BALF) and sharply reduced the intensity of bronchoconstriction to histamine challenge. L-NAME also significantly decreased the NO production in the BALF, but had no effect on airway reactions or, perhaps, a tendency to enhance the intensity of AHR. CONCLUSIONS: The data suggest that inducible NOS contributes to the AHR induced by repetitive intraperitoneal LPS, and constitutive NOS was also involved.

Differential expressions of nNOS and iNOS in the rostral ventrolateral medulla induced by electroacupuncture in acute myocardial ischemia rats.

Increasing lines of evidence has been accumulated that nitric oxide (NO) and nitric oxide synthase (NOS) distribute plentifully in the rostral ventrolateral medulla (RVLM) and contribute to cardiovascular regulation. In the present study, the expressions of neuronal and inducible isoform of NOS (nNOS and iNOS) were observed in the RVLM of acute myocardial ischemia (AMI) Wistar rats experienced electroacupuncture (EA) treatment, thereby the cardiovascular effects of NO in the RVLM were investigated and the mechanism of acupuncture effect on AMI was inferred. The results indicated that in the AMI rats, cardiac functions were markedly attenuated with high serum level of brain natriuretic peptide (BNP) and norepinephine (NE), the number of nNOS-immunoreactive cells and nNOS mRNA exprossion in the RVLM area were increased, while those of iNOS were lowered. EA at "Neiguan" acupoints (Pe 6) 30 min daily for successive 5 d resulted in an improvement of the cardiac functions, decreases in NE and BNP levels; it also increased the expression of iNOS and decreased the expression of nNOS in the RVLM. These results suggest that the curative effect of acupuncture on AMI is possibly attributable to the differential regulation of NOS/NO in the RVLM, leading to decreased sympathetic outflow and improvement of cardiac functions.

The protective effects of electro-acupuncture in thoracic surgery on trauma stressed rats involve the rostral ventrolateral medulla and supraoptic nucleus.

The present study was designed to explore whether the rostral ventrolateral medulla (RVLM) and supraoptic nucleus (SON) were involved in the protective effects of electro-acupuncture (EA) in thoracic surgery on trauma-stressed rats. The rats were randomly divided into a non-stressed group (Control), surgical trauma-stressed group (Trauma), and Neiguan EA applied on the surgical trauma-stressed group (Trauma+EA-PC 6). RVLM neuron discharge was observed by using an in vivo electrophysiological method, and micro-dialysis combining high-performance liquid chromatography with fluorometric detection (HPLC-FD) was used to assess expression of amino acids in the RVLM. Immunohistochemical methods were used to assess c-Fos expression in SON neurons. The trauma of surgical stress was shown to dramatically increase the discharge frequency of RVLM neurons and promote the release of glutamate and taurine in the RVLM. The expression of c-Fos was also significantly increased in the SON of traumatized rats. EA application at Neiguan acupoints significantly suppressed trauma-induced increase of discharge frequency of the RVLM neurons, almost completely suppressed the trauma-induced increase of glutamate release but only very slightly reduced the trauma-enhanced taurine release, and inhibited the increase of c-Fos expression in these SON neurons of traumatized rats. These results indicate that Neiguan EA may improve cardiac function by modulating neurons in the RVLM and the SON in surgically traumatized rats. The taurine-mediated negative feedback may be involved in the protective effect of EA on cardiac function.

Effect of adrenomedullin on the activity of barosensitive neurons in the rostral ventrolateral medulla of rats.

To investigate the eletrophysiological effect of rat adrenomedullin (rADM) on barosensitive neurons in the rostral ventrolateral medulla (rVLM) and its potential mechanisms, the extracellular recording and multi-barrel iontophoresis methods were used. Of the 29 barosensitive neurons in the rVLM, 20 neurons demonstrated excitatory response to iontophoretically applied rADM and increased the firing rate from (10.8 +/- 2.7) spikes/s to (14.6 +/- 3.6), (19.8 +/- 4.7) and (31.9 +/- 6.4) spikes/s (P<0.05, n=20) at the current of 30, 60 and 90 nA, respectively. Application of human adrenomedullin (22-52) [hADM (22-52)], a specific antagonist of rADM receptor, distinctly attenuated the augmentation of firing rate induced by rADMjthe firing rate was increased by 15.4% [(11.4 +/- 2.5) spikes/s, P<0.05, n=10]. Another antagonist, human calcitonin gene-related peptide (8-37) [hCGRP (8-37)] had no significant effect on rADM-induced excitation. Other 23 barosensitive neurons were recorded to test the influence of nitric oxide synthase (NOS) inhibitors on the excitatory effect of rADM. In 10 neurons, 7-NiNa (neuronal NOS inhibitor) decreased the firing rate from (10.1 +/- 3.5) spikes/s to (7.5 +/- 2.5), (5.3 +/- 2.1) and (3.1 +/- 1.4) spikes/s (P<0.05, n=10) at the current of 10, 20 and 40 nA, respectively. The excitatory effect of rADM (60 nA, 30 s) during 7-NiNa application was nearly eliminated and the magnitude of firing rate was increased only by 17% of the basal level (6.2 +/- 1.9) spikes/s (P<0.05, n=7). While aminoguanidine (AG, iNOS inhibitor) increased the firing rate at the resting level from (11.5 +/- 5.1) spikes/s to (17.8 +/- 5.6), (22.5 +/- 6.3) and (29.1 +/- 6.4) spikes/s (P<0.05, n=8) at the current of 10, 20 and 40 nA in 8 barosensitive neurons, respectively. When rADM (60 nA, 30 s) was delivered during AG iontophoresis period, the firing rate significantly increased by 60% of the basal level [(22.5 +/- 6.3) spikes/s, n=5]. These results indicate that rADM activates the barosensitive neurons in the rVLM directly and acts as a cardiovascular regulator, and that this function might be mediated by its specific receptor. NO, mainly neuronal NOS-originated might be involved in the excitatory effect of rADM in the rVLM.

Amino acids modulate the hypotensive effect of angiotensin-(1-7) at the caudal ventrolateral medulla in rats.

The present experiment was designed to investigate the possible involvement of glutamate and taurine in the depressor response produced by angiotensin (Ang)-(1-7) at the caudal ventrolateral medulla (CVLM) in rats anesthetized with urethane and alpha-chloralose. Microinjection of Ang-(1-7) into the CVLM elicited a depressor response which was partially blocked by nonselective glutamate receptors antagonist kynurenic acid, whereas selective Ang-(1-7) antagonist Ang779 produced a pressor response which was significantly attenuated by taurine receptors antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide. Release of glutamate and taurine in the CVLM was evaluated with microdialysis, and the contents of these amino acids were measured with high performance liquid chromatography-fluorescent detection. The depressor response to Ang-(1-7) was accompanied by an increased release of glutamate and a decrease of taurine at the CVLM, whereas the pressor response to Ang779 was associated with a decreased release of glutamate and an increase of taurine. These results suggest that Ang-(1-7) and its antagonist Ang779 modulate the release of glutamate and taurine at the CVLM, which in turn contributes at least in part to the blood pressure response to Ang-(1-7) and Ang779.

Effects of acupuncture on nNOS and iNOS expression in the rostral ventrolateral medulla of stress-induced hypertensive rats.

This study was to observe the changes of the neuronal and inducible nitric oxide synthase (nNOS & iNOS) as well as their mRNAs in the rostral ventrolateral medulla (RVLM) of stress-induced hypertensive rats before and after acupuncture, and thereby to infer the curative mechanism of acupuncture on hypertension. The result indicated that the systolic blood pressure (SBP) of stress group rats was increased significantly (P < 0.01), it was accompanied that the expression of nNOS in the RVLM, including the immunoreactive neuron number (P < 0.05), the optical density (OD) (P < 0.01), and the mRNA (P < 0.01) were obviously elevated, while those of iNOS (P < 0.05, P < 0.01 and P < 0.01) were evidently lowered in the stress-induced hypertensive rats. Electroacupuncture (EA) points at "Zusanli" (St. 36) and "Lanwei" (Extra 37) on the same hindlimb were stimulated by an EA apparatus (Type G6805-2) with dense sparse wave (4-20Hz) and 4mA intensity. EA application could return the SBP (P < 0.05), and the changes on the expression of both nNOS and iNOS (P < 0.05, P < 0.01 and P < 0.01). These results suggest that the curative mechanism of acupuncture on stress-induced hypertension is related to the changes of nNOS and iNOS in the RVLM of rats.

Expression of angiotensin II type 1 (AT(1)) receptor in the rostral ventrolateral medulla in rats.

In the present study, the changes of amino acids release in the spinal cord after the application of angiotensin II (ANG II) in the rostral ventrolateral medulla (RVLM) and the distribution of ANG receptors on neurons of the RVLM were investigated. A microdialysis experiment showed that microinjection of angiotensin II into the RVLM significantly (P < 0.01) increased the release of aspartate and glutamate in the intermediolateral column of the spinal cord. Immunofluorescence technique combined with confocal microscopy demonstrated that most of the glutamatergic and GABAergic neurons in the RVLM of both Wistar and spontaneously hypertensive rats (SHR) were double labeled with ANG type 1 (AT1) receptor. Immunocytochemical studies demonstrated that the mean optic density of AT1 receptor of the cell surface as well as the whole cell was higher (P < 0.05) in SHR than that in Wistar rats, indicating that the higher expression of AT1 receptors in the RVLM may contribute to the higher responsiveness of SHR to ANG II stimulation. Immunogold staining and electronmicroscopic study demonstrated that AT1 receptor in the RVLM was distributed on the rough endoplasmic reticulum, cell membrane, and nerve processes. The results suggest that effects evoked by ANG II in the RVLM are closely related to glutamatergic and GABAergic pathways. These results indirectly support the hypothesis that ANG II in the RVLM may activate vasomotor sympathetic glutamatergic neurons, leading to an increase in sympathetic nerve activity and arterial blood pressure.

Changes of adrenomedullin and its receptor components mRNAs expression in the brain stem and hypothalamus-pituitary-adrenal axis of stress-induced hypertensive rats.

In this study, reverse transcription-polymerase chain reaction (RT-PCR) was used to detect the changes in mRNAs levels of preproadrenomedullin (ppADM) gene encoding adrenomedullin (ADM) and the essential receptor components of ADM, calcitonin receptor-like receptor (CRLR), and the receptor activity modifying protein 2 and 3 (RAMP2 and RAMP3) in the medulla oblongata, hypothalamus, midbrain, pituitary gland and adrenal gland of the stress-induced hypertensive rats. It was shown that chronic foot-shock and noise stress for 15 consecutive days induced a significant increase in systolic blood pressure (SBP) and unique changes in ppADM and its receptor components mRNAs in all areas studied. As compared with the control group, the level of ppADM mRNA, normalized against a glyceraldehydes-3-phosphate dehydrogenase (GAPDH) control, was up-regulated in the hypothalamus-pituitary-adrenal (HPA) axis, but down-regulated in the medulla oblongata and midbrain (P<0.01 and P<0.05, respectively). The relative amount of CRLR mRNA was higher in the hypothalamus than that in other areas. The level of CRLR mRNA expression was significantly increased in the medulla oblongata of the stress group (P<0.01), but decreased in the midbrain (P<0.01) as well as hypothalamus(P<0.05), as compared with that of the control group. Chronic stress for 15 consecutive days produced an increase in the level of RAMP2 mRNA expression in the medulla oblongata (P<0.01) and a decrease in the adrenal gland (P<0.01), as compared with the control. No significant stress-related changes in RAMP2 mRNA were observed in the midbrain, hypothalamus and pituitary gland. The amount of RAMP3 mRNA was relatively higher in the midbrain and hypothalamus than that in the medulla oblongata, adrenal gland and adrenal gland. Stress-induced hypertensive rats exhibited an increased RAMP3 mRNA expression in the hypothalamus and pituitary gland (P<0.01 and P<0.05, respectively) and a decrease in the adrenal gland and midbrain (P<0.05). No significant stress-related change in RAMP3 mRAN was observed in the medulla oblongata. Taken together, our results indicate that the significant changes in ppADM and its receptor components mRNAs expression in the HPA axis and autonomic centers may be related to the development of the stress-induced hypertension. Nevertheless, the pathophysiological significance of brain-derived ADM and its receptors in stress and blood pressure regulation and their roles in stress-induced hypertension still await further investigation.

Medullary ventrolateral nitric oxide mediates the cardiac effect of electroacupuncture at "Neiguan" acupoint on acute myocardial ischemia in rats.

Experiments were performed on male Sprague-Dawley (SD) rats anesthetized with a mixture of urethane and chloralose. A rat model of acute myocardial ischemia (AMI) was made by ligation of the left anterior descending branch of the coronary artery (LAD). After the LAD ligation, the ischemia area of the left ventricular wall became somewhat pale immediately. Under a light microscope, the pathological examination revealed that all the cells were swollen and in red color when the cardiac section was stained with hematoxylin basic fuchsin picric acid (HBFP), which indicated a typical change in the myocardial ischemia. In the AMI model, it was found that cardiac functions were markedly attenuated, such as decreases in the heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), maximal rate for left ventricular pressure rising and declining (+/-dp/dt(max)), velocity of contractile element (V(CE)) and total area of cardiac force loop (L(0)), and an increase in the left ventricular end diastolic pressure (LVEDP). In such AMI rats, application of electroacupuncture (EA) at "Neiguan" acupoints (Pe 6) for 20 min could obviously improve the above-mentioned cardiac functions. After microinjection of nitro-L-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS), was made into the rostral ventrolateral medulla (RVLM), the curative effect of EA on myocardial ischemia was reduced significantly or abolished, while after microinjection of normal saline of the same volume was made into the RVLM, the improving effect of EA remained. These results suggest that the effect of EA on myocardial ischemia is possibly mediated by the nitric oxide (NO) in the RVLM.

Effects of electroacupuncture on pressor response to angiotensin-(1-7) by amino acid release in the rostral ventrolateral medulla.

Unilateral microinjection of Angiotensin-(1-7)[Ang-(1-7)] into the rostral ventrolateral medulla (RVLM) of anesthetized rats caused an increase in mean arterial pressure (MAP) accompanied by an increased release of excitatory amino acid (EAA) glutamate. In contrast, microinjection of Ang779, a selective antagonist of Ang-(1-7) receptor, into the RVLM caused a decrease in MAP accompanied by a deceased release of EAA glutamate as well as an increased release of inhibitory amino acid (IAA) glycine, taurine and gamma-aminobutyric acid. After electroacupuncture (EA) stimulation at "Zusanli"(St.36) for 20 min, the above effects of Ang-(1-7) or Ang779 attenuated. These results suggest that attenuation of EA on the pressor effect of Ang-(1-7) or the depressor effect of Ang779 may be through regulating the corresponding amino acid neurotransmitter release in the RVLM.

Simvastatin pretreatment protects cerebrum from neuronal injury by decreasing the expressions of phosphor-CaMK II and AQP4 in ischemic stroke rats.

Excitotoxicity and cytotoxic edema are the two major factors resulting in neuronal injury during brain ischemia and reperfusion. Ca2+/calmodulin-dependent protein kinase II (CaMK II), the downstream signal molecular of N-methyl-D-aspartate receptors (NMDARs), is a mediator in the excitotoxicity. Aquaporin 4 (AQP4), expressed mainly in the brain, is an important aquaporin to control the flux of water. In a previous study, we had reported that pretreatment of simvastatin protected the cerebrum from ischemia and reperfusion injury by decreasing neurological deficit score and infarct area (Zhu et al. PLoS One 7:e51552, 2012). The present study used a middle cerebral artery occlusion (MCAO) model to further explore the pleiotropic effect of simvastatin via CaMK II and AQP4. The results showed that simvastatin reduced degenerated cells and brain edema while decreasing the protein expressions of phosphor-CaMK II and AQP4, and increasing the ratios of Bcl-2/Bax, which was independent of cholesterol-lowering effect. Immunocomplexes formed between the subunit of NMDARs-NR3A and AQP4 were detected for the first time. It was concluded that simvastatin could protect the cerebrum from neuronal excitotoxicity and cytotoxic edema by downregulating the expressions of phosphor-CaMK II and AQP4, and that the interaction between NR3A and AQP4 might provide the base for AQP4 involving in the signaling pathways mediated by NMDARs.

Repeated electroacupuncture attenuating of apelin expression and function in the rostral ventrolateral medulla in stress-induced hypertensive rats.

Studies have revealed that apelin is a novel multifunctional peptide implicated both in blood pressure (BP) regulation and cardiac function control. Evidence shows that apelin and its receptor (APJ) in the rostral ventrolateral medulla (RVLM) may play an important role in central BP regulation; however, its role is controversial and very few reports have shown the relationship between acupuncture and apelin. Our study aims to both investigate the apelinergic system role in stress-induced hypertension (SIH) and determine whether acupuncture therapy effects on hypertension involve the apelinergic system in the RVLM. We established the stress-induced hypertensive rat (SIHR) model using electric foot-shock stressors with noise interventions. The expression of both apelin and the APJ receptor in the RVLM neurons was examined by immunohistochemical staining and Western blots. The results showed apelin expression increased remarkably in SIHR while APJ receptor expression showed no significant difference between control and SIHR groups. Microinjection of apelin-13 into the RVLM of control rats or SIHR produced pressor and tachycardic effects. Furthermore, effects induced by apelin-13 in SIHR were significantly greater than those of control rats. In addition, repetitive electroacupuncture (EA) stimulation at the Zusanli (ST-36) acupoint attenuated hypertension and apelin expression in the RVLM in SIHR; it also attenuated the pressor effect elicited by exogenous apelin-13 microinjection in SIHR. The results suggest that augmented apelin in the RVLM was part of the manifestations of SIH; the antihypertensive effects of EA might be associated with the attenuation of apelin expression and function in the RVLM, which might be a novel role for EA in SIH setting.

Effects of electroacupuncture at Zusanli (ST36) on inflammatory cytokines in a rat model of smoke-induced chronic obstructive pulmonary disease.

OBJECTIVE: Improvement in lung function was reported after acupuncture treatment of chronic obstructive pulmonary disease (COPD), but little is known about the underlying mechanisms. Because an immune response imbalance could be seen in COPD, we hypothesize that electroacupuncture (EA) may play a role in regulating inflammatory cytokines and contribute to lung protection in a rat model of smoke-induced COPD. METHODS: A COPD model using male Sprague-Dawley rats exposed to cigarette smoke was established. The rats were randomly divided into four groups (control, sham, COPD, and COPD plus EA), and COPD model was evaluated by measuring pulmonary pathological changes and lung function. EA was applied to the acupuncture point Zusanli (ST36) for 30 min/d for 14 d in sham and COPD rats. Bronchoalveolar lavage fluid (BALF) was used to measure levels of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and malonaldehyde (MDA). RESULTS: Compared with the control rats, COPD rats had significant changes in lung resistance (RL) and lung compliance (CL) (both P<0.01), bronchi and bronchiole airway obstruction (P<0.01), and levels of MDA, TNF-α, and IL-1ß (P<0.01). There were no significant differences between the control and the sham groups. Compared with the COPD rats, the COPD plus EA rats had decreased RL and increased CL (both P<0.05), and reduced bronchi and bronchiole airway obstruction (P<0.05, P<0.01, respectively), while levels of TNF-α, IL-1ß, and MDA in BALF were lowered (P<0.05 and P<0.01, respectively). However, TNF-α and IL-1ß levels of the EA group rats remained higher than those of the control group (P<0.05). CONCLUSION: EA at ST36 can reduce lung injury in a COPD rat model, and beneficial effects may be related to down-regulation of inflammatory cytokines. The anti-inflammatory and antioxidant effects may prolong the clinical benefit of EA.

Protective effects of electroacupuncture on cardiac function in rats subjected to thoracic surgery trauma.

The present study investigates the protective effects of electroacupuncture (EA) application on cardiac function, while simultaneously exploring the underlying neurobiological mechanisms, in rats that have experienced thoracic surgery-induced stress. Mean arterial and left intraventricular pressures were monitored as indicators of cardiac function. Meanwhile, the immunohistochemistry for c-Fos protein expression and electrophysiology in vitro in brain nuclei, known to regulate cardiac function, provide insights into the effects of EA on the central nervous system. The results show that cardiac function was dramatically suppressed with thoracic surgery trauma, the expression levels of c-Fos in the paraventricular nucleus (PVN) and the rostral ventrolateral medulla (RVLM) significantly increased, the rheobase intensity of the intracellular current injection needed to initiate the action potential decreased, membrane resistance in the PVN neurons significantly increased, and the inductivity of the postsynaptic potentials in the PVN neurons of the surgery-treated rats significantly decreased. EA application at the Neiguan acupoints (PC6) attenuated the decreases in almost all investigated functional parameters of the heart. EA significantly decreased the number of Fos-immunoreactive neurons in the PVN and RVLM, significantly decreased the Max L. slope of the PVN neurons, and increased the inductivity of the postsynaptic potentials in the PVN neurons of the surgery-treated rats. These data indicate the protective effects of EA application on cardiac function in rats that have experienced surgery-induced stress and show that EA application at the Neiguan acupoints may produce its protective effects through the neurons in the PVN and the RVLM.