Huttenlocher P R, Bonnier C
Department of Pediatrics, University of Chicago, IL 60637.
Brain Res Dev Brain Res. 1991 Jun 21;60(2):253-60. doi: 10.1016/0165-3806(91)90054-m.
Effects of changes in the periphery on development of the corticospinal (CS) motor system were studied in the rat. Unilateral forelimb restraint between ages 5 and 30 days resulted in an increase in the number of CS neurons which persisted in the adult. The effect was most marked ipsilateral to limb restraint where both crossed and uncrossed CS connections were increased, but it also occurred to a lesser extent on the contralateral side. Animals with limb restraint had enlargement of the areas of cerebral cortex in which CS neurons occurred. The enlargement of motor cortex regions and increase in CS neurons closely resembled the changes found in the remaining cerebral hemisphere after neonatal hemispherectomy. The findings in animals with forelimb restraint differed markedly from those after forelimb amputation, where little change occurred in either number or location of CS neurons. Limb restraint initiated at the time of postnatal hemispherectomy had no effects on location or number of CS neurons beyond those of hemispherectomy alone. It is proposed that transient CS axons that occur normally in the postnatal rat may be recruited for formation of permanent connections under very diverse conditions, i.e. hemispherectomy and limb restraint. Failure to observe an additional effect of limb restraint in hemispherectomized animals may be due to the fact that after hemispherectomy all available transient fibers in the remaining hemisphere are recruited for innervation of the side of the spinal cord that has lost its cortical input.
在大鼠中研究了外周变化对皮质脊髓（CS）运动系统发育的影响。5至30日龄之间的单侧前肢约束导致CS神经元数量增加，这种增加在成年期持续存在。该效应在肢体约束同侧最为明显，交叉和未交叉的CS连接均增加，但在对侧也有较小程度的发生。肢体受约束的动物中，CS神经元所在的大脑皮质区域增大。运动皮质区域的增大和CS神经元数量的增加与新生儿半球切除术后在剩余大脑半球中发现的变化非常相似。前肢受约束动物的研究结果与前肢截肢后的结果明显不同，在前肢截肢后，CS神经元的数量和位置几乎没有变化。出生后半球切除时开始的肢体约束对CS神经元的位置或数量没有产生超出单独半球切除的影响。有人提出，正常情况下在出生后大鼠中出现的短暂CS轴突可能在非常不同的条件下（即半球切除和肢体约束）被募集用于形成永久连接。在半球切除的动物中未观察到肢体约束的额外影响，可能是因为在半球切除后，剩余半球中所有可用的短暂纤维都被募集用于支配失去皮质输入的脊髓侧。
