Weiler M H, Williams K D, Peterson R E
Toxicol Appl Pharmacol. 1986 Jun 30;84(2):220-31. doi: 10.1016/0041-008x(86)90129-8.
Effects of 2,4-dithiobiuret (DTB) treatment in rats on neuromuscular transmission and the disposition of cholinergic substances, acetylcholine (ACh) and choline (Ch), were examined in a combined electrophysiological/biochemical study using an in vitro extensor digitorum longus (EDL) muscle-peroneal nerve preparation. EDL muscle preparations isolated from rats treated with DTB (1 mg/kg/day X 5 days, ip) displayed a 49% depression in the frequency of miniature end-plate potentials (MEPPs) and a 21% depression in mean MEPP amplitude. Statistical analysis of evoked end-plate potentials (EPPs) measured in curarized preparations indicated that the mean quantal content (m) was significantly depressed in EDL muscles from DTB-treated rats. At stimulation rates of 1, 10, 20, and 50 Hz the estimated values of m in EDL preparations from DTB-treated rats were, respectively, 21, 25, 45, and 51% of that in control preparations. Biochemical determinations of ACh and Ch revealed a significant DTB-induced increase in endogenous ACh and Ch content in EDL preparations fixed for extraction of ACh and Ch immediately after dissection from the treated rats. In vitro, however, there were negligible changes in overall ACh synthesis since the total (tissue and medium) tracer ACh (2H4-ACh) synthesized from tracer Ch (2H4-Ch; 10 microM) supplied in the perfusion medium was similar in EDL preparations from DTB-treated and control rats. Also, in EDL muscles from DTB-treated rats the resting release of ACh was not affected, but when exogenous Ch (2H4-Ch) was not supplemented in the medium the evoked release (via peroneal nerve stimulation) of ACh was depressed. Thus, decreases in spontaneous quantal ACh release, as detected in the electrophysiological experiments, were not reflected by changes in the biochemically determined ACh resting release. The biochemical determination of evoked ACh release, however, correlated with the decrease in quantal content detected in the electrophysiological analysis of evoked EPPs when exogenous Ch was not supplemented in the perfusion medium. Significant and consistent increases (two to three times) in both Ch content and efflux occurred in the EDL muscles from DTB-intoxicated rats. These results indicate that DTB induces a prejunctional impairment of neuromuscular transmission that is not specifically directed at ACh synthesis. Rather those processes by which ACh is incorporated into or released from vesicles appear to be altered.
采用体外趾长伸肌（EDL）-腓神经制备方法，通过电生理/生化联合研究，检测了2,4-二硫代双缩脲（DTB）对大鼠神经肌肉传递以及胆碱能物质乙酰胆碱（ACh）和胆碱（Ch）代谢的影响。从经DTB（1mg/kg/天×5天，腹腔注射）处理的大鼠分离得到的EDL肌肉制备物，微小终板电位（MEPPs）频率降低49%，平均MEPP幅度降低21%。对箭毒化制备物中诱发终板电位（EPPs）的统计分析表明，DTB处理大鼠的EDL肌肉中平均量子含量（m）显著降低。在1、10、20和50Hz的刺激频率下，DTB处理大鼠的EDL制备物中m的估计值分别为对照制备物的21%、25%、45%和51%。对ACh和Ch的生化测定显示，DTB处理导致从处理大鼠处取材后立即固定用于提取ACh和Ch的EDL制备物中内源性ACh和Ch含量显著增加。然而，在体外，总体ACh合成变化可忽略不计，因为在灌注培养基中由示踪剂Ch（2H4-Ch；10μM）合成的总（组织和培养基）示踪剂ACh（2H4-ACh）在DTB处理和对照大鼠的EDL制备物中相似。此外，DTB处理大鼠的EDL肌肉中ACh的静息释放未受影响，但当培养基中不补充外源性Ch（2H4-Ch）时，（通过腓神经刺激）诱发的ACh释放受到抑制。因此，电生理实验中检测到的自发量子ACh释放减少，并未在生化测定的ACh静息释放变化中体现出来。然而，当灌注培养基中不补充外源性Ch时，诱发ACh释放的生化测定与诱发EPPs电生理分析中检测到的量子含量降低相关。DTB中毒大鼠的EDL肌肉中Ch含量和外流均显著且持续增加（两到三倍）。这些结果表明，DTB诱导神经肌肉传递的接头前损伤，且并非特异性针对ACh合成。相反，ACh被纳入囊泡或从囊泡释放的过程似乎发生了改变。
