[Progress of Researches on Central Mechanism of Electroacupuncture Tolerance]

Electroacupuncture (EA) has been demonstrated effective for pain relief. However, repeated application may decline analgesic effect of EA, which is termed EA tolerance, that reduces the clinical efficacy of EA. Therefore, it has attracted attention from researchers in recent years and the progresses include:(1) acute and chronic EA tolerance animal models have been established; (2) cross-tolerance between EA and morphine; (3) Anti-opioid substances, including cholecystokinin, orphanin FQ and angiotensin Ⅱ, have been reported to contribute to EA tolerance; (4) glutamate receptors and transporters, 5-hydroxytryptamine and norepinephrine have been revealed involvement in EA tolerance; (5) cyclic adenosine monophosphate, cyclic guanosine monophosphate and Ca²⁺ have been reported to be the second messengers cellularly in EA tolerance. The current EA tolerance effect lacks in-depth researches. Therefore, studies on its molecular mechanisms and signaling pathway are necessarily required.