Study on the protective effect and mechanism of electroacupuncturing at Zusanli point (足三里) on endotoxin induced hepatic injury in rats

Objective: To investigate the protective effect and mechanism of electroacupuncturing (EA) at Zusanli (足三里, ST36) on endotoxin induced hepatic injury in rats. Methods: Seventy male Wistar rats were randomly divided into seven groups (each n=10): ①sham control, ②lipopolysaccharide (LPS) alone, ③LPS+EA, ④LPS+vagotomy, ⑤LPS+vagotomy+EA, ⑥LPS+α-bungarotoxin (α-BGT) and ⑦LPS+α-BGT+EA. All animals except those in sham control were injected Gram-negative bacteria O111∶B4 LPS 5 mg/kg into the caudal vein to produce hepatic injury. Zusanli point (ST36) were electro-acupunctured with constant voltage (2-100 Hz, 2 mA for 1.5 hours) immediately in group ③,⑤ and ⑦ after LPS challenge. Bilateral cervical vagotomy was performed in rats in group ④and ⑤. α-BGT (1 μg/kg), an antagonist of cholinergic N receptor α7 subunit was injected into vena caudalis for animals in group ⑥ and ⑦ after LPS injection. All animals were sacrificed at 2 hours after LPS injection. The content of tumor necrosis factor-α (TNF-α) in liver tissue and the activity of alanine aminotransferase (ALT) in plasma were detected. Results: LPS injection resulted in significant increase of TNF-α in liver tissue and ALT in plasma. EA at Zusanli point obviously lowered the increase of TNF-α and ALT (both P0.05), and alleviated hepatic insult at 2 hours after LPS challenge. Injection of α-BGT or vagotomy could weaken or eliminate the effects of EA. Conclusion: It is suggested that cholinergic anti-inflammatory pathway be one of the main mechanisms of hepatic protective effect of EA at ST36.