Electroacupuncture induces differential effects between Yin and Yang: a study using cutaneous blood flow and temperature recordings of the hand's dorsum and palm.

The underlying theory of traditional Chinese Medicine (TCM) considers that Yin and Yang are in the opposition with each other and play different roles in physiological responses. Several studies have reported that electroacupuncture (EA) produces a greater effect than manual acupuncture (MA), and that the effect of EA is similar to transcutaneous electric nerve stimulation (TENS). Therefore, the purpose of the present study was to investigate the differences between Yin and Yang induced by acupuncture. A total of 20 healthy volunteers were studied. The cutaneous blood flow and temperature were recorded by a laser doppler perfusion and temperature monitoring system on the dorsum and palm of the right hand. Four sessions of sham acupuncture (SA), MA, 2 Hz EA, and 2 Hz TENS were bilaterally applied to Zusanli (ST36) and Shangjuxu (ST37) acupoints. Each of the subjects received four sessions in a random manner. The treatment interval was at least three days between sessions in order to prevent overlapping residual effects. Each of the four sessions was divided into pre-acupuncture period (BP), acupuncture period (AP), and post-acupuncture (PP) periods. Each treatment period was 15 min. Results indicated that the cutaneous blood flow recorded from the palm of the hand were greater than that recorded from the dorsum at the pre-acupuncture period; while the difference in the cutaneous temperature from the dorsum of the hand between AP and BP was greater in the 2 Hz EA session than in the SA and MA sessions. In conclusion, the results of the present study were consistent with the underlying theory of TCM that considers the fundamental differences between Yin and Yang.