Vagal withdrawal and/or sympathetic overactivity is always accompanied by various kinds of stress and is dangerous to the body. We proposed that mild acupuncture on the Sishencong points may effectively enhance vagal activities but suppress sympathetic regulations of the heart in humans. Experiments were carried out on nine healthy male volunteers, while they were lying in a quiet room during 2-4 P.M. Acupuncture was applied 2 mm deep into the skin using standard stainless acupuncture needles at the Sishencong points, which are located on the vertex of the head, each 1 cm away from Baihui (GV 20) in four directions. Four points around the temporal area were selected as control points. Forty minutes of precordial ECG signals before, during, and after acupuncture were recorded continuously. Frequency-domain analysis of the stationary RR intervals was performed to evaluate the total variance, high-frequency power (HF, 0.15-0.40 Hz) and low-frequency power (LF, 0.04-0.15 Hz) in normalized units (LF%). Acupuncture on the Sishencong points resulted in an increased HF but a decreased LF% compared with the before acupuncture stage. Such effects did not occur when manual acupuncture was applied to the control points. The differences in the heart rate dynamics between Sishencong and the control groups took place 10 min after initiation of acupuncture and persisted even after the removal of the needles. Based on these results, we concluded that manual acupuncture on the Sishencong points enhanced cardiac vagal and suppressed sympathetic activities in humans. The underlying mechanisms and potential applications warrant further investigations.
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