Effects of perineurial block of sciatic nerve with different concentrations of alcohol on structure and function of the nerve and its innervated muscles in rats

Abstract

Objective To observe the concentration effects of alcohol in perineurial block on the structure and function of sciatic nerve and it's innervated muscles in rats so as to provide the basis for clinical application of chemical neurolysis.Methods One hundred and fifty female Sprague-Dawley rats were used and randomly assigned into a blank group(BG,n =6),a control group(CG,n =36),a 50％ alcohol group(50G,n =36),a 75％ alcohol group(75G,n =36)and a 99.9％ alcohol group(99.9G,n =36).The CG received physiological saline injection,the 50G,75G,99.9G received corresponding concentrations alcohol perineurial block,respectively.Changes of motor function was assessed,electrophysiological and histomorphological observations of sciatic nerve and its innervated muscles were conducted before and at 24 h,72 h,1 week,4 week,12 week after block.Results(① Hypokinesia and decrease of motor conduction velocity(MCV)were observed at 24 h after block,and peaked at 72 h after block; at 1 week after block,the motor function and MCV improved,the improvement persisted to the 12th week (P ＜ 0.05); but at the 12th week,MCV was still slower than that before block(P ＜ 0.01).②There were significant differences with regard to motot function and MCV of sciatic nerve among 99.9G and the other groups at e ery time point after block(P ＜0.05); ③ Reversible dengeneration of sciatic nerve and hind limb muscle,nonreversible necrosis of muscle occurred more seriously with the increase of alcohol concentration,and the cicatrization in 99.9G was more obvious than that in 50G and 75G at the 12th week; ④Structural lesion of sciatic nerve occurred at 24 h after block and peaked at the 72th h,myelinated axonal sprouts appeared at 1 week after block and persisted to the 12th weck.Conclusions ① The effects of 99.9 ％ alcohol perineural block on the structural lesion,motor function and MCV of sciatic nerve and its related muscle were more obvious than those of 50％ and 75％ alcohol; ② The destructive effect of alcohol block would maintain more than 12 week and neural restoration would maintain more than 12 weeks too. Key words: Alcohol; Sciatic nerve ; Nerve block ; Motor conduction velocity