The Comparisons For The Sensitivity To Rocuronium Among Facial Nerve Dominated Orbicularis Oris Muscle And Gastrocnemius Muscle In Rats.

Objective:To compare the differerence of sensitivity to non-depolarizing muscle relaxant rocuronium among isolated normal or injuried facial nerve dominated orbicularis oris or gastrocnemius muscle in rats to provide theory for partial neuromuscular blockade's application in surgery requiring facial nerve monitoring.Methods:Adult SD rats were used in this experiment(Fudan University animal lab center,cleaning degree),weighted 180-220g,anesthetized with ketamine 20mg/kg and diazepam 20mg/kg by peritoneal injection.The right facial nerve injury was induced by the method of trunk crushing with 10 rats,the left was set as normal control group.The normal and injuried side orbicularis oris and normal gastrocnemius muscle strips were isolated and perfused 95%O2 and 5%CO2 in thermostatic bath filled with Kreb's nutrient solution(NaCl 135;KCl 5;CaCl2 2; NaHCO3 15;Na2HPO4 1;MgSO4 1;glucose 11;mmol/L),PH 7.3. One end was fixed to L hook while the other end was connected with tonotransducer by thread.The indirect electrical stimulation evoked muscular tension amplitude(MTA) was recorded by SMUP-PC biological signal processing system.After resting for 30 minutes,the fundamental MTA and MTA under rocuromiun concentration equal to rat's blood drug level 0.5ED₉₅,ED₉₅,1.5ED₉₅,2ED₉₅ was recorded.Every rocuromiun concentration was incubated for at least 15 minutes.The changes of MTA from the three groups of strips under different concentrations of rocuromiun were observed and expressed by the percentage of muscular tension amplitude inhibition(MTAI%).Using self-contrast control,the percentage of muscular tension amplitude inhibition(MTAI%) was set as ordinates,rocuromiun's logarithmic dose as abscissa to get the dose-response curve between the percentage of muscular tension amplitude inhibition(MTAI%) and rocuronium concentration.Results:Increased MTAI%of the three groups of strips was detected after rocuronium incubation in a dose-dependent manner. Under 2.5ug/ml,5ug/ml,7.5 ug/ml and 10 ug/ml concentration of recuronium(equal to rat's blood drug level 0.5ED95,ED95,1.5ED95,2ED95),the MTAI%of the gastrocnemius was higher than the MTAI%of orbicularis oris muscle(P＜0.05).Especially under concentration of recuronium equal to rat's blood drug level 1×ED95,the MTAI%of the gastrocnemius was higher than the MTAI%of orbicularis obviously.But no statistically significant difference was found between normal or injuried facial nerve dominated orbicularis oris.The pathologic examination for normal and injuried facial nerve tissues by HE staining under oil immersion objective(10×20) showed facial nerve injury with vacuolar degeneration in Schwann Cells,morphological changing in myelin sheath,RBC gathering in myelin sheath gap and interspersed Neural Stem fibre fracture and the pathologic examination for facial nerve tissues under transmission electron microscopy PHILIPS CM-120(×4000 ) showed vacuolar degeneration, uncomplete myelin sheath vacuolar degeneration,uneven axon staining and Schwann Cells morphologically change.Those were accorded with the characteristic of nerve injury. Conclusion:Facial nerve dominated orbicularis oris was less sensitive to rocuronium than gastrocnemius.This kind of difference was not found between normal and injuried facial nerve dominated orbicularis oris.