Anti-hyperalgesic effect of electroacupuncture in a model of post-incisional pain in rats

Electroacupuncture has been proposed to be a low cost and practical method that allows effective pain management with minimal collateral effects. In t his study we have examined the effect of electroacupuncture against the hyp eralgesia developed in a model of postincisional pain in rats. A 1-cm longi tudinal incision was made through the skin and fascia of the plantar region of the animal hind paw. Mechanical hyperalgesia in the incision was evalua ted 135 min after the surgery with von Frey filaments. The tension threshol d was reduced from 75 g (upper limit of the test) to 1.36 +/- 0.36 g (mean +/- SEM) in control rats. It is shown that a 15-min period of electroacupun cture applied 120 min after surgery to the Zusanli (ST36) and Sanyinjiao (S P6) points, but not to non-acupoints, produces a significant and long-lasti ng reduction of the mechanical hyperalgesia induced by the surgical incisio n of the plantar surface of the ipsilateral hind paw. The tension threshold was reduced from 75 to 27.6 +/- 4.2 g in animals soon after the end of ele ctroacupuncture. The mechanical threshold in this group was about 64% less than in control. Electroacupuncture was ineffective in rats treated 10 min earlier with naloxone (1 mg/kg, ip), thus confirming the involvement of opi oid mechanisms in the antinociceptive effects of such procedure. The result s indicate that post-incisional pain is a useful model for studying the ant ihyperalgesic properties of electroacupuncture in laboratory animals.