Simultaneous acupuncture to two or more acupoints has been used to improve acupuncture-induced effects in clinical practice. However, there is little evidence supporting the effects of simultaneous electroacupuncture (EA). This study examined whether simultaneous EA with 2 and 2 Hz or 2 and 100 Hz can produce synergic effects on ankle-sprained pain in rats.

Ankle sprain pain was induced by manually overextending the lateral ligament of the right ankle in rats. Electrical stimulation with 2 Hz was delivered to the Yangno acupoint (SI6) and with 2 or 100 Hz to the Zusanli (ST36), either individually or simultaneously. The level of pain evoked by the ankle sprain was measured by the stepping force of the sprained paw during walking. The analgesic effects of simultaneous EA was evaluated by the percentage recovery of the stepping force at 1, 2 and 4hr after EA and compared to that of individual EA.

Individual EA significantly increased the stepping force of the ankle-sprained paw during walking, but there is no difference in the effect between electrical stimulation with 2 and 100 Hz EA. Simultaneous EA with 2 and 2 Hz or 2 and 100 Hz showed no significant improvement of the stepping force compared to individual EA.

Individual EA with 2 and 100 Hz produced comparable analgesic effects. Simultaneous EA applied to the SI6 and ST36 acupoints produced no synergic interaction, therefore has no beneficial effect for ankle-sprained pain compared to individual EA.