Barthélemy Dorothy, Cabana Thérèse
Département de Sciences Biologiques, Université de Montréal, C.P. 6128, Succ. Centre-ville, Montréal, Québec, Canada H3C 3J7.
Brain Res Dev Brain Res. 2005 Mar 31;155(2):87-98. doi: 10.1016/j.devbrainres.2004.12.008.
The development of limb motor innervation was studied in the opossum Monodelphis domestica, a marsupial born with immature mobile forelimbs and immobile hindlimbs. Choline acetyltransferase (ChAT), the synthesis enzyme of acetylcholine, was evidenced on sections of the spinal enlargements, and the protein that transports acetylcholine (VAChT) on limb sections. In newborn, ChAT immunolabeling occurred in small, undifferentiated neurons of the ventral horn, presumably motoneurons, and intermediate and dorsal gray matter, and in the presumptive white matter, all less abundant at lumbosacral than brachial levels. Scant immunolabeling for VAChT marked small terminal-looking profiles, presumably growth cones or immature neuromuscular junctions, decreasing proximodistally in each limb and being less abundant in hindlimbs than forelimbs; it was absent distally in the foot where no muscle tissue was formed. ChAT labeling disappeared from the white matter within 1 week while cholinergic neurons increased in number and size. Motoneurons segregated in a medial and lateral group by 4-5 weeks. VAChT-labeled profiles increased in number and size and they flattened along a proximodistal gradient within each limb, but later in the hindlimbs than in the forelimbs. Labeling appeared in distal foot muscle at 1 week. The density, size, and shape of terminals became comparable in all segments of a given limb by 3-4 weeks. Their number and size increased, and by 8 weeks, they clustered in 3 or 4 along muscle fibers. Thus, limb motor innervation develops largely postnatally in the opossum, along rostrocaudal and proximodistal gradients. Its timecourse is compared to the development of motor behaviors.
在负鼠短尾负鼠（Monodelphis domestica）中研究了肢体运动神经支配的发育情况，这种有袋动物出生时前肢可活动但不成熟，后肢则不能活动。在脊髓膨大切片上证实了乙酰胆碱合成酶胆碱乙酰转移酶（ChAT）的存在，在肢体切片上证实了转运乙酰胆碱的蛋白质（囊泡乙酰胆碱转运体，VAChT）的存在。在新生负鼠中，ChAT免疫标记出现在腹角的小的、未分化的神经元（推测为运动神经元）以及中间和背侧灰质中，在推测的白质中也有出现，所有这些在腰骶部的丰度均低于臂部水平。VAChT的免疫标记很少，标记出小的终末样轮廓，推测为生长锥或不成熟的神经肌肉接头，在每个肢体中从近端向远端逐渐减少，在后肢中的丰度低于前肢；在没有形成肌肉组织的足部远端没有VAChT标记。ChAT标记在1周内从白质中消失，而胆碱能神经元的数量和大小增加。运动神经元在4 - 5周时分为内侧和外侧两组。VAChT标记的轮廓数量和大小增加，并且它们在每个肢体中沿近端到远端的梯度变平，但后肢比前肢出现得晚。1周时在足部远端肌肉中出现标记。到3 - 4周时，给定肢体所有节段中终末的密度、大小和形状变得相当。它们的数量和大小增加，到8周时，它们沿着肌纤维聚集成3或4个。因此，负鼠的肢体运动神经支配在很大程度上是在出生后沿着头尾和近端到远端的梯度发育的。将其时间进程与运动行为的发育进行了比较。
