梭曼引起大鼠膈肌终板区持续性去极化

在大鼠离休不均匀牵张膈肌标本（ＩＮＳＭＰ）上,选择接近正常电生理学状态的神经肌肉接头,研究了梭曼引起的串终板电位（ＴＥＰＰ）变化,观察到．梭曼浓度在５．５ｎｍｏｌ·Ｌ１到５５μｍｏｌ。Ｌ１范围内,间接串刺激时除在少数标本上出现ＴＥＰＰ幅度降低的第一种反应外,在大多数标本上出现持续性去极化（ＳＤ）．ＳＤ过程中,终板电位（ＥＰＰ）完全消失,ＳＤ－旦出现,持续时间相对稳定,具有“全或无”性质,梭曼浓度在５５ｎｍｏｌ·Ｌ到５５μｍｏｌ·Ｌ范围内,反应以ＳＤ为主（＞８０％）大鼠一个致死量梭曼中毒（０,１ｍｇ·ｋｇ１ｉｍ）后制备ＩＮＳＭＰ,间接串刺激时也产生这两种反应,仍以ＳＤ为主（９１％）冲洗掉残余梭曼,对ＳＤ各参数无影响,再加入高浓度梭曼（５５μｍｏｌ·Ｌ１）时,４５％标本上ＳＤ转化为第一种反应,另５５％标本上ＳＤ的７０％时程缩短至４２％,再冲洗梭曼后１００％标本上ＳＤ恢复。结果表明,ＳＤ与第一种反应有质的区别．ＳＤ是梭曼抑酶作用的结果,高浓度梭曼可能对神经肌肉接头有直接作用,但不是梭曼中毒的主要因素,ＳＤ是梭曼中毒后,间接串刺激时ＴＥＰＰ的主要变化,是在突触电位水平上梭曼等胆碱酯酶抑制剂中毒致神经肌肉传递阻断的?

Sustained depolarization in end-plate area of rat diaphragm induced by soman

In the isoldted nonuniform stretchedmuscle preparation(INSMP)of rat diaphragm,somecnd- plates which are close to the physiological condi-tion of neuromuscular junction electrophysiologicallywere selected to investigate the changes of traincnd-plate potentials(EPPs)after the intoxication ofsoman Two types of distinguished changes of trainEPPs in response to repetitive nerve stimulations(50Hz × 1s) were observed in the intoxicated preparationwith 5.5 pmol·L 1 soman. The first-type change wasthat the amplitudes of EPPs decreased while thepostsynaptic area was depolarized to a certain degree. But the membrane potential repolarized rapidly afterthe cease of stimulations、Its 70%duration was 0.45 ±50.09 s(n=3)The first-type change was cbssical be-cause it had been studied in detail by many autbors.The second-type change was that only the first 1-3EPPs could be recorded and followed by a prolongedplateau of depolarization(its 70%duration was 3.0 ± s1.6s,n=55) during which no EPPs could be recorded. The second-type change was named " sustaineddepolarizdtion, SD" according to the feature of re-sponse,because the mechanism of SD was not clear. SD was evoked after 5.5 nmol·L1 55 μmol·L1 soman and was the dominant response in morethan 80% of total end plates tested in the soman con-centration range of 55 nmol·L1 55 μmol·L1.Thefirst type change was recorded in less than 20%end-plates. In INSMP from rats intoxicttted withsoman(0.1mg·kg\im).SD waso the doininantresponse(10 / 11,91%)The parameters of SD werenot changed afler lhe washing of soman. But the 70%duration of SD was reduced to 42y, dfter 55 μmol·L soman in 55%end plates, and SD turned out tobe the first type change in the other 45% end platesSD was restored in 100% end plates after the washingof 55 μmol·L soman High concentration of somanhad direct effects on neuromusctilar junction,but SD isnot the result of soman's direct effect It is suggestedthat SD reslts from the inhibition of acetylcho-linesterase activity aftersomam And SD is the domi-nant change of truin EPPs after soman or other AChEinhibitor intoxication