Effects of Electroacupuncture at PC6 and ST36 on Heart Rate Variability in Anesthetized Mice

Objective: To observe the change of heart rate variability in anesthetized mice after electroacupuncture on PC6 and ST36, and compare the difference between these points. Methods: A total of 33 C57BL/6 mice were randomly divided into control, PC6 and ST36 groups with 11 mice in each group. The electrocardiogram was recorded by two needle electrodes. The HRV data were analyzed by time and frequency analysis with heart rate, Standard Deviation of R-R Intervals and LF/HF Ratio. Result: During the EA at PC6, SDRR was significantly increased (P < 0.05) and maintained with a significantly higher level at the end of experiment, and the LF/HF ratio was gradually increased throughout the experiment. During the EA at ST36, SDRR was significantly increased (P < 0.05) and there was no observable tendency of the change in LF/HF ratio during the experiment. In comparison with control, the HR of group PC6 mice decreased significantly during EA stimulation (P < 0.01) and continued declining throughout the experiment (P < 0.05). Time spectral analysis of the ECG recordings showed that control mice had significantly lower SDRR compared to group PC6 and group ST36 after EA stimulation(P < 0.05). SDRR was significantly increased when measured at 90mins after EA in group PC6 in comparison with control (P < 0.01). EA at PC6 caused a significant increase than ST36 in SDRR when measured at Stim. (P < 0.05) and 90mins after EA (P < 0.01). Conclusion: EA at PC6 and ST36 protected anesthesia mice against decline of HRV. In comparison with ST36, the effect of EA at PC6 was more significant, which was caused by the increase of the sympathetic nerve activities from the postganglionic fibers with the same spinal cord segments to heart.