新霉素及链霉素对神经肌肉接头的作用及其对抗梭曼的作用(英文)

Effects of neomycin and streptomycin on neuromuscular transmission and their antagonism against soman

在不均匀牵拉的离体大鼠膈肌标本上观察了氨基甙类抗菌素新霉素和链霉对终板电位(EPP)和微终板电位(MEPP)的影响和对不可逆胆碱酯酶抑制剂索曼的对抗作用。新霉素减低EPP量子含量,抑制MEPP幅度和减慢MEPP放电频率的浓度相应为0.03,0.1和0.32 mmol/L。链霉素抑制EPP和MEPP相应比新霉素强50和30倍。不影响量子含量的阈下剂量的新霉素(0.015mmol/L)和链霉素(0.8 mmol/L)能部分预防梭曼减少量子含量的作用。再增加此两药的浓度不能提高它们对抗梭曼的效用.同样,不影响MEPP频率的阈下剂量的新霉素和链霉素能完全预防梭曼加快MEPP频率的作用。认为新霉素和链霉素对神经肌接头抑制作用的主要作用部位是突触前递质诱发释放系统。其机理可能是它们竞争性地减少梭曼引起的向突触前膜内Ca^(2+)内流的增加。它们预防梭曼增加MEPP频率的机理也可能是如此。

The effects of aminoglycosidcs,neomycin and streptomycin,on endplate potential(EPP)and miniature endplate potential(MEPP)and their antagonism against soman,an irreversible anticholincstcrasc,were studied in isolated nonuniform stretched muscle preparation of rat diaphragm.The concentrations of neomycin for reducing the quantal content of EPP,depressing the MEPP amplitude and decreasing the MEPP frequency were 0.03 mmol/L,0.1 mmol/L and 0.32 mmol/L,respectively.The concentrations of streptomycin were about 50 times and 30 times higher for depressive effects on EPP and MEPP,respectively,than those of neomycin.0.015 mmol/L neomycin and 0.8 mmol/L streptomycin,i.e.subthreshold dose,could partially prevent the soman-induced reduction of EPP quantal content and the antagonistic effect was not increased when the drug concentrations were further raised above the threshold level.The subthreshold concentration of neomycin and streptomycin for slowing the MEPP frequency could prevent the soman-induced acceleration of frequency.It is suggested that the primary site of the blocking effect on ncuromuscular junction of neomycin and streptomycin is the presynaptic evoked transmitter release mechanism.This may be related to a competitive antagonism against soman-induced over influx of calcium into presynaptic membrane of nerve terminal by neomycin and streptomycin.The same mechanism may be considered for their antagonism against soman-induced presynaptic depression of spontaneous transmitter release.