Orexin Receptor-1 in the Rostral Ventrolateral Medulla Mediates the Antihypertensive Effects of Electroacupuncture.

Electroacupuncture (EA) has been used to treat numerous diseases, including hypertension. This study aimed to investigate the long-term effect and underlying mechanisms of EA stimulation at the LI11 point on the hypertension and sympathetic nerve activity in two-kidney, one-clip (2K1C) hypertensive rats. EA (0.1-0.4 mA, 2 and 15 Hz) was applied to the acupoints LI11 overlying the deep radial nerve once a day for 6 weeks. The mean arterial pressure (MAP) and heart rate (HR) were determined by radiotelemetry, and the sympathetic nerve activity was evaluated by telemetric analyses of the low-frequency component of blood pressure (BP) and by plasma epinephrine and norepinephrine levels. The results showed 6 weeks of EA significantly lowered the increased BP effectively, inhibited the enhanced sympathetic nerve activities and attenuated cardiac hypertrophy in 2K1C hypertensive rats. The level of orexin receptor-1 (OX1R) in the rostral ventrolateral medulla (RVLM) after EA treatment was markedly reduced in 2K1C rats, while there was no difference in the RVLM expression of orexin receptor-2 (OX2R) in 2K1C and 2K1C+EA rats. Moreover, the increased pressor and depressor responses to microinjection of orexin A or OX1R antagonist SB408124 into the RVLM of 2K1C rats were significantly blunted by the EA treatment. These findings suggest that BP-lowering effect of EA on renovascular hypertension may be through inhibition of central sympathetic activities and modulation of functional orexin receptors in the RVLM.

Electroacupuncture Improves Baroreflex and γ-Aminobutyric Acid Type B Receptor-Mediated Responses in the Nucleus Tractus Solitarii of Hypertensive Rats.

Electroacupuncture (EA) has been reported to benefit hypertension, but the underlying mechanisms are still unclear. We hypothesized that EA attenuates hypertension, in part, through modulation of γ-aminobutyric acid (GABA) receptor function in the nucleus tractus solitarii (NTS). In the present study, the long-term effect of EA on GABA receptor function and expression was examined in the NTS of two-kidney, one-clip (2K1C) renovascular hypertensive rats. EA (0.1-0.4 mA, 2 and 15 Hz) was applied at Zusanli (ST36) acupoints overlying the deep fibular nerve for 30 min once a day for two weeks. The results showed that long-term EA treatment improved blood pressure (BP) and markedly restored the baroreflex response in 2K1C hypertensive rats. The increased pressor and depressor responses to microinjection of GABAB receptor agonist and antagonist into the NTS in the hypertensive rats were blunted by the EA treatment. Moreover, EA treatment attenuated the increased GABAB receptor expression in the NTS of hypertensive rats. In contrast, EA had no significant effect on the GABAA receptor function and expression in the NTS of 2K1C hypertensive rats. These findings suggest that the beneficial effects of EA on renovascular hypertension may be through modulation of functional GABAB receptors in the NTS.

Electrical signal propagated across acupoints along Foot Taiyang Bladder Meridian in rats.

OBJECTIVE: To investigate the electrical signals propagated along Foot Taiyang Bladder Meridian (BL) in a rat model. METHODS: The experiments were performed on Dark-Agouti (DA), DA.1U and Sprague Dawley (SD) rats. The antidromic electrical stimulation was applied on the nerve innervating "Pishu" (BL 20) to mimic the acupoint electro-acupuncture (EA). The activities recording from adjacent nerve innervating acupoint "Danshu" (BL 19) or "Weishu" (BL 21) were recorded as indics for acupoint, including the mechanical threshold and discharge rate. RESULTS: After mimic EA on BL 20, C and Aδ units from adjacent BL 19 or BL 21 were sensitized including the decrease in mechanical threshold and increase in discharge rates in DA, DA.1U and SD rats, especially in DA rats. The average discharge rate increased from 2.40±0.26 to 6.06±0.55 and from 1.92±0.42 to 6.17±1.10 impulse/min (P<0.01), and the mechanical threshold decreased from 0.52±0.12 to 0.24±0.05 and from 0.27±0.02 to 0.16±0.01 mmol/L (P<0.01) in C (n=15) and Aδ (n=18) units in DA rats. The net change in discharge rates from C units were 152.5%, 144.7% and 42.4% in DA, DA.1U and SD rats, respectively, among which DA rat's was the highest (P<0.05). In Aδ units, the net change in DA rats were also the highest (221.5%, 139.2% and 49.2% in DA, DA.1U and SD rats). CONCLUSIONS: These results showed that mimic acupoint EA activated adjacent acupoints along BL in three rat strains, which might be related to propagated sensation along meridians (PSM). In addition, DA rats were more sensitive and might be a good model animal for PSM research.

Polydatin supplementation ameliorates diet-induced development of insulin resistance and hepatic steatosis in rats.

The pathophysiology of non-alcoholic fatty liver disease remains to be elucidated, and the currently available treatments are not entirely effective. Polydatin, a stilbenoid compound derived from the rhizome of Polygonum cuspidatum, has previously been demonstrated to possess hepatoprotective effects. The present study aimed to determine the effects of polydatin supplementation on hepatic fat accumulation and injury in rats fed a high-fat diet. In addition, the mechanisms underlying the protective effects of polydatin were examined. Male Sprague Dawley rats were randomly divided into four groups and received one of four treatment regimes for 12 weeks: Control diet, control diet supplemented with polydatin, high-fat diet, or high-fat diet supplemented with polydatin. Polydatin was supplemented in the drinking water at a concentration of 0.3% (wt/vol). The results of the present study showed that long-term high-fat feeding resulted in fatty liver in rats, which was manifested by excessive hepatic neutral fat accumulation and elevated plasma alanine aminotransferase and aspartate aminotransferase levels. Polydatin supplementation alleviated the hepatic pathological changes, and attenuated the insulin resistance, as shown by an improved homeostasis model assessment of basal insulin resistance values and a glucose tolerance test. Polydatin supplementation also corrected abnormal leptin and adiponectin levels. Specifically, polydatin supplementation enhanced insulin sensitivity in the liver, as shown by improved insulin receptor substrate 2 expression levels and Akt phosphorylation in the rat liver, following high-fat diet feeding. The results of the present study suggest that polydatin protects rats against high-fat feeding-induced insulin resistance and hepatic steatosis. Polydatin may be an effective hepatoprotective agent and a potential candidate for the prevention of fatty liver disease and insulin resistance.

Angiotensin-(1-7) attenuates the chronotropic response to angiotensin II via stimulation of PTEN in the spontaneously hypertensive rat neurons.

Several studies have focused on the beneficial effects of peripheral angiotensin-(1-7) [Ang-(1-7)] in the regulation of cardiovascular function, showing its counterregulatory effect against the actions of angiotensin II (ANG II). However, its actions in the central nervous system are not completely understood. In the present study, we investigated the intracellular mechanisms underlying the action of ANG-(1-7) using the patch-clamp technique in neurons cultured from the hypothalamus of neonatal spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Superfusion of neurons with ANG II (100 nM) significantly increased neuronal firing in both strains of rats, and this chronotropic effect of ANG II was significantly enhanced in prehypertensive SHR neurons compared with WKY rat neurons. The enhanced chronotropic effect of ANG II was attenuated by a phosphatidylinositol 3-kinase (PI3-kinase) inhibitor, LY 294002 (10 µM). Superfusion of neurons with ANG-(1-7) (100 nM) did not alter the neuronal firing rate in either SHR or WKY neurons; however, it significantly attenuated the chronotropic action of ANG II exclusively in prehypertensive SHR neurons. This counterregulatory effect of ANG-(1-7) on ANG II action in prehypertensive SHR neurons was attenuated by cotreatment with either A-779, a Mas receptor antagonist, or bisperoxovanadium, a phosphatase and tensin homologue deleted on chromosome ten (PTEN) inhibitor. In addition, incubation of WKY and prehypertensive SHR neurons with ANG-(1-7) significantly increased PTEN activity. The data demonstrate that ANG-(1-7) counterregulates the chronotropic action of ANG II via a PTEN-dependent signaling pathway in prehypertensive SHR neurons.

Lentil polyphenol extract prevents angiotensin II-induced hypertension, vascular remodelling and perivascular fibrosis.

The objective of the study was to investigate whether chronic administration of the Morton lentil polyphenol extract (MLPE), which possesses rich phenolic compounds and a high antioxidant activity, had any protective effects on angiotensin II-induced hypertension. After four weeks of subcutaneous infusion of angiotensin II (200 ng kg(-1) min(-1)) in male SD rats, the water intake and mean artery pressure was significantly increased by 39.8% and 48.3%, respectively, as compared with the control. The media/lumen ratio of the small arteries in the heart and kidneys were increased by 117% and 168% by angiotensin II infusion. The perivascular fibrosis was increased by 65% and 32% in the heart and kidneys, respectively. Levels of the reactive oxygen species in the aorta was enhanced by 115.8%. In another group of rats, which received four weeks of lentil extract administration (1% freeze-dried MLPE in the drinking water), followed by another four weeks of extract administration plus angiotensin II infusion, the angiotensin II-induced enhancement in water intake and mean artery pressures decreased by 12.7% and 8.2%, respectively, as compared with the rats that received angiotensin II infusion alone. The angiotensin II-induced rats showed increases in the media/lumen ratios which were attenuated by 43.6% and 47.2% in the small arteries of heart and kidneys, respectively. Angiotensin II-induced perivascular fibrosis was attenuated by 30% and 26% in the rats that received the extract. Angiotensin II-induced rats showed reactive oxygen species levels in the aorta was reduced by 48.9%. These findings demonstrated that lentil extract attenuated angiotensin II-induced hypertension and associated pathological changes, including remodelling and perivascular fibrosis in the small resistant arteries of heart and kidneys.

Morton lentil extract attenuated angiotensin II-induced cardiomyocyte hypertrophy via inhibition of intracellular reactive oxygen species levels in vitro.

The objective was to investigate whether a lentil (Morton) extract had any protective effect on cardiac hypertrophy, which is one of the most significant sequelae of cardiovascular diseases. High phenolic compounds (43.4 mg of GAE/g), including thirteen phenolic acid and two flavonoids, were detected in the acetone/water/acetic acid lentil extract. The extract showed strong antioxidant ability (105 µmol of TE/g). The effect of lentil extract on angiotensin (Ang) II-induced cardiac hypertrophy was examined. Results showed that pretreatment with lentil extract (25, 50, 100 µg/mL) significantly attenuated Ang II (0.1 µM)-induced hypertrophy by 18, 28, and 36% in rat cardiomycytes, respectively; lentil extract (12.5, 25, 50 µg/mL) attenuated Ang II (0.1 µM)-induced hypertrophy by 9, 17, and 25% in human cardiomycytes, respectively. Intracellular reactive oxygen species (ROS) levels were enhanced by Ang II treatment, and this stimulatory action was significantly attenuated (33% inhibition) by lentil extract (100 µg/mL) in rat cardiomyocytes and attenuated by 22% by 50 µg/mL lentil extract in human cardiomyocytes. In conclusion, Morton lentil extracts attenuated Ang II-induced rat and human cardiomyocytes hypertrophy via decreasing intracellular ROS levels.

Mechanical hyperalgesia is attenuated by local administration of octreotide in pristane-induced arthritis in Dark-Agouti rats.

AIMS: The Dark-Agouti (DA) rat is very susceptible to pristane-induced arthritis (PIA) and represents a suitable model for rheumatoid arthritis. In the present study, we examined the pain sensitivity and the effect of local administration of octreotide (OCT) on mechanical hyperalgesia in PIA DA rats. MAIN METHODS: Arthritis was induced by intradermal injection of pristane (300 microl). The mechanical withdrawal threshold (MWT) and heat withdrawal latency (HWL) were used to evaluate the pain sensitivity. In addition, we recorded the discharge firings in the tibial nerve sensory C-fibers innervating the inflamed toe joints of arthritic DA rats. KEY FINDINGS: Two weeks after injection of pristane, all DA rats developed severe arthritis. This symptom was associated with a decreased MWT (78.50+/-5.68 mN before pristane injection, 19.50+/-6.27 mN on day 14 after pristane injection), indicating a mechanical hyperalgesia in PIA. In contrast, HWL was comparable before and after pristane injection (10.25+/-0.70 s before injection; 9.45+/-1.23 s on day 14 after injection). Local injection of OCT markedly increased MWT and relieved the hyperalgesia in PIA. In addition, OCT significantly decreased the discharge rate of afferent C units evoked by both non-noxious and noxious joint movements. SIGNIFICANCE: Taken together, the results demonstrate that mechanical hyperalgesia, but not thermal hyperalgesia is associated with PIA and that the mechanical hyperalgesia and the discharge of afferent C units are attenuated by local administration of OCT. These observations provide evidence for a novel therapeutic strategy for pain control in rheumatoid arthritis.