Abstract 413: Electroacupuncture Improves Arterial Baroreflex and Chemoreflex Sensitivity in Angiotensin II-induced Hypertension in Rats

Abstract

Despite the use of electroacupuncture (EA) to treat a number of cardiovascular diseases, little is known about the mechanisms that underlie its actions. It is well known that renin-angiotensin system plays a major role in pathogenesis of hypertension. The purpose of this study was to examine the influence of EA stimulation of ST 36 on arterial baro- and chemoreflex sensitivity in angiotensin (Ang) II-induced hypertension in rats. Four groups of SD rats (n=8/group) were implanted with subcutaneous osmotic minipumps for infusion of Ang II (300 ng/kg/min) or saline control, with or without EA stimulation. EA groups underwent a 2 Hz EA treatment at the acupoints ST36 or a non-acupoint with the intensity increasing stepwise from 0.5-1-1.5 mA once a day for 30 min. Baroreflex sensitivity index was calculated on the basis of reflex changes in heart rate (HR) related to the arterial pressure (AP) changes induced by phenylephrine or sodium nitroprusside injection, and chemoreflex sensitivity was evaluated by intravenous injections of increasing doses of potassium cyanide (KCN). After 4 weeks of treatment, Ang II significantly increased mean arterial pressure (107±2 and 139±2 mmHg in control vs. Ang II group). Baroreflex sensitivity to AP rises and falls were also impaired in Ang II infusion group (1.3±0.08 and 2.1 ±0.18 bpm/mmHg) compared with those in control group (1.7±0.08 and 2.7±0.06 bpm/mmHg). EA stimulation of ST 36 on Ang II infusion rats significantly improved the impaired baroreflex sensitivity (1.7±0.06 and 2.6±0.1 bpm/mmHg, P < 0.05). In addition, the bradycardic and pressor responses evoked by KCN injections were attenuated in Ang II infusion rats (23±9 bpm and 7±1 mmHg in Ang II group vs. 78±7 bpm and 22±3mmHg in control group, P < 0.05), while EA stimulation improved both chemoreflex responses in AngII rats (84±15 bpm and 32±5 mmHg, P<0.05). In contrast, EA stimulation had no significant effect on control group. These results indicate that EA stimulation improves arterial baroreflex function and chemoreflex sensitivity in conditions of high Ang II.