Kullberg R, Owens J L, Vickers J
J Physiol. 1985 Jul;364:57-68. doi: 10.1113/jphysiol.1985.sp015729.
The effect of chronic immobilization on the development of synaptic currents was studied in myotomal muscle of Xenopus laevis. Embryos and tadpoles were immobilized by rearing them in the presence of tetrodotoxin (TTX) after removal of the egg membranes. Immobilization did not affect the developmental change in duration of miniature end-plate currents (m.e.p.c.s). Rise times decreased from about 3 to 0.6 ms in both immobilized and control muscle, and decay constants decreased from about 7 to 1 - 2 ms in both conditions. M.e.p.c.s with double exponential decays were recorded in both immobilized and control muscle at intermediate and late developmental stages. The fast and slow decay constants were 0.7 ms and slightly less than 3 ms in older muscle of both groups. These values are comparable to the apparent open times of fast and slow ACh receptors present on Xenopus muscle. Application of an anticholinesterase (methanesulphonyl fluoride) lengthened the duration of m.e.p.c.s comparably in immobilized and control muscle. These data indicate that the deposition of junctional acetylcholinesterase and the reduction in open time of acetylcholine receptor channels in developing Xenopus myotomal muscle are independent of contractile activity of muscle and TTX-blockable action potentials in muscle or motoneurones.
在非洲爪蟾的肌节肌中研究了慢性固定对突触电流发育的影响。去除卵膜后，将胚胎和蝌蚪饲养在含有河豚毒素（TTX）的环境中使其固定。固定并不影响微小终板电流（m.e.p.c.s）持续时间的发育变化。在固定肌肉和对照肌肉中，上升时间均从约3毫秒降至0.6毫秒，衰减常数在两种情况下均从约7毫秒降至1 - 2毫秒。在发育中期和后期，在固定肌肉和对照肌肉中均记录到具有双指数衰减的m.e.p.c.s。两组较老肌肉中的快速和慢速衰减常数分别为0.7毫秒和略小于3毫秒。这些值与非洲爪蟾肌肉上快速和慢速乙酰胆碱受体的表观开放时间相当。应用抗胆碱酯酶（甲磺酰氟）在固定肌肉和对照肌肉中同等程度地延长了m.e.p.c.s的持续时间。这些数据表明，在发育中的非洲爪蟾肌节肌中，接头乙酰胆碱酯酶的沉积以及乙酰胆碱受体通道开放时间的缩短与肌肉的收缩活动以及肌肉或运动神经元中可被TTX阻断的动作电位无关。
