Effect of electroacupuncture on St. 36 (Zusanli) and LI. 10 (Shousanli) acupuncture points on heart rate variability.

Electrical stimulation of St. 36 (Zusanli) has been shown to enhance the regularity of gastric myoelectrical activity in healthy subjects. However, the underlying mechanism by which acupuncture alters gastric myoelectrical activity is still not clear. To elucidate the possible role of the autonomic nervous system in mediating the effect of acupuncture, we monitored heart rate variability (HRV), a widely used index of vagal discharge at the sinoatrial node of the heart before, during and after electroacupuncture. In this study, we applied two different frequencies (2 Hz and 100 Hz) of electrical stimulation at St. 36 (Zusanli) and LI. 10 (Shousanli) in 15 healthy volunteers. Low frequency (LF, sympathetic activity), high frequency (HF, vagal activity) and LF/HF ratio (sympathovagal balance) were analyzed and compared at the two different frequencies. The results showed an increase in the LF/HF ratio (indicating greater sympathetic activity) during the post-acupuncture period using 2 Hz of electrical stimulation at St. 36 (Zusanli). However, the overall change was not statistically significant. In addition, the power of LF and HF did not change significantly with electroacupuncture at St. 36 (Zusanli) and LI. 10 (Shousanli). In conclusion, applying 2 Hz or 100 Hz electroacupuncture at St. 36 (Zusanli) or LI. 10 (Shousanli) did not affect cardiovagal activity in normal volunteers. This phenomenon might be due to a difference in presentation in the autonomic nervous system between cardiac and abdominal vagal activity.