The Study on the Analgesic Effect and its Cholinergic Mechanism of Electroacupuncture in the Rat Model of Collagen-induced Arthritis

Collagen 유발(誘發) 관절염(關節炎) 동물모델에 대(對)한 전침자극(電鍼刺戟)의 진통효과(鎭痛效果) 및 그 기전(機轉)에 관(關)한 연구(硏究)

Objectives : To investigate the analgesic effect and its cholinergic mechanism of electroacupuncture(EA) in the rat model of collagen-induced arthritis(CIA). Methods : Immunization of male Sprague-Dawley rats with bovine typeII (CII) collagen emulsified in Freund's incomplete adjuvant, followed by a booster injection 14 days later, leads to development of arthritis in more than 70% of rats by 21 days postinjection. After three weeks of first immunization, EA stimulation(2 Hz, 0.07 mA, 0.3 ms) was delivered into Jogsamni($ST_{36}$) for 30 minutes. Analgesic effect was evaluated by tail flick latency(TFL). We compared the analgesic effect of EA with TFLs between pretreatment of normal saline and pretreatment of Atropine (1 mg/kg, intraperitoneal) and Neostigmine ($100{\mu}g/kg$, intraperitoneal) in CIA. Results : 1. TFLs were gradually decreased in CIA as increasing severity of arthritis. 2. Jogsamni($ST_{36}$) EA stimulation in CIA increased TFLs and the effect lasted for 60 minutes. 3. Increased TFLs with Jogsamni($ST_{36}$) EA stimulation were inhibited with pretreatment of atropine in CIA 4. Increased TFLs with Jogsamni($ST_{36}$) EA stimulation did not show an obvious synergistic effect with pretreatment of neostigmine in CIA. Conclusions: Jogsamni($ST_{36}$) EA showed analgesic effects in CIA. The analgesic effects of Jogsamni($ST_{36}$) EA were inhibited by atropine pretreatment and combined application of Jogsamni(ST36) EA and neostigmine did not show an synergistic effect. These observations suggest that intrinsic muscarinic cholinergic pathways represent an important modulating system in pain perception of inflammatory pain in CIA It is suggested that, the active mechanism of analgesic effect in EA may involve the release of acetylcholine in the spinal cord.