Abstract
Although electroacupuncture (EA) at several acupoints including Zusanli is known to have sympathoinhibitory effect, inter-individual differences and time-dependent changes in the responsiveness make the quantitative application of EA difficult. We examined if we could control the stimulus intensity of EA based on its effect on arterial blood pressure (BP). In five anesthetized cats, we identified the transfer function from EA to BP using a white noise analysis, and designed a feedback controller of the EA stimulus intensity based on a proportional integral controller. The controller adjusted the stimulus current (1-5 mA) to minimize the difference between measured and target BP values. A nonlinear threshold effect of the BP response to EA was avoided by adjusting the stimulus frequency simultaneously (0-10 Hz). When we set the target level at 20 mmHg below baseline BP, the developed system was able to reduce BP within a minute with a steady-state error of 1.2±0.2 mmHg (mean±SE) for 10 min. During the period of the feedback control, renal sympathetic nerve activity was remained suppressed at 78±5% of the baseline level. The quantitative application of EA to suppress sympathetic nerve activity would contribute to treat several cardiovascular diseases accompanying sympathetic overactivity. [J Physiol Sci. 2008;58 Suppl:S159]
