[A study of the regularity of pain threshold changes after trauma and the effect of electroacupuncture]

Pain threshold of rats was measured by the latent period of tail flick and limb withdrawal elicited by radiant heat. 52 male SD rats were used and trauma was produced by aseptic amputation just beneath the right ankle joint. The effect of nerve block and electroacupuncture (EA) was studied and non-traumatic groups were arranged as control. The pain threshold was reduced right after trauma and the lowest level appeared on the 3rd day and then recovered gradually up to the 7th day after trauma. Nerve block and EA markedly raised the pain threshold. Particularly, EA elevated pain threshold of traumatic rats more marked and long-lasted than the effect of nerve block. This may be resulted by mobilizing the functions of the endogenous analgesic systems.