DEVELOPMENT OF NEUROMUSCULAR-JUNCTIONS IN RAT EMBRYOS
DEVELOPMENT OF NEUROMUSCULAR-JUNCTIONS IN RAT EMBRYOS
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DOI：
10.1016/0012-1606(81)90290-6
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发表时间：
1981-01-01
影响因子：
2.7
通讯作者：
HARRIS, AJ
中科院分区：
文献类型：
--
作者：
DENNIS, MJ;ZISKINDCONHAIM, L;HARRIS, AJ
本文研究了孕13-21天大鼠胚胎和新生大鼠肋间肌神经-肌肉接头的生理特性。妊娠第13天，神经束长入肌肉区域。第13-14天开始出现肌管。肌管在出生前就被电耦合，从而允许去极化在纤维之间横向传播。偶联强度随胎龄的增加而下降，出生后消失。在早期，相邻节段的一些纤维也是端对端耦合的。肌管的静息电位从它们出现的时间起就很高（70-90 mV）。在妊娠第14天，在一些肌管中记录到微型终板电位。在那个时候，神经刺激也可以引起终板电位，这是能够触发肌肉收缩。从个别终端释放的递质的平均量子含量是小相比，在成人肌肉，它仍然很小，通过出生后第1周。单个肌纤维在其中心附近有一个单一的终板部位，可以接收多达6个不同的突触输入。每根纤维的输入数在妊娠第17天达到峰值，然后在出生前开始下降，在出生后第2周内达到其成人值1输入/纤维。肋间内肌含有. apprx。30个运动单位，每个局限于肌肉的一个小区域。单个运动单位所占区域的大小并没有随着每根纤维突触输入数量的减少而明显减小。在妊娠第17天，40%的肌肉含有1个或多个异常运动单位，其母轴突通过相邻节段的前根伸出。这些单位的消除开始在同一时间的突触输入到单个肌纤维和70%的异常单位的数量减少出生前消除。
Physiological properties of nerve-muscle junctions were studied in intercostal muscles of rat embryos of 13-21 days gestation and in neonates. Nerve bundles grew into the muscle region by day 13 of gestation. Myotubes began to appear on days 13-14. Myotubes were electrically coupled before birth, allowing the spread of depolarization laterally between fibers. The strength of coupling declined with embryonic age and disappeared after birth. At early times, some fibers of adjacent segments were also coupled, end-to-end. Resting potentials of myotubes were high (70-90 mV) from the time of their appearance. Miniature end-plate potentials were recorded in some myotubes on day 14 of gestation. At that time also, nerve stimulation could evoke an end-plate potential which was capable of triggering muscle contraction. The mean quantal content of transmitter released from individual terminals was small compared to that in adult muscle; it remained small through the 1st postnatal wk. Individual myofibers had a single end-plate site near their center, which could receive as many as 6 distinct synaptic inputs. The number of inputs per fiber reached a peak at day 17 of gestation and then began to decline before birth, reaching its adult value of 1 input/fiber within the 2nd postnatal wk. The internal intercostal muscles contained .apprx. 30 motor units, each confined to a small zone in the muscle. The region occupied by a single motor unit was not obviously reduced in size as the number of synaptic inputs per fiber declined. At day 17 of gestation, 40% of the muscles contained 1 or more aberrant motor units, the parent axons of which projected out through the ventral roots of adjacent segments. Elimination of these units commenced at the same time as did the reduction in number of synaptic inputs to single myofibers and 70% of the aberrant units were eliminated before birth.