Department of Anatomy, Philadelphia, PA 19120 (U.S.A.).
Restor Neurol Neurosci. 1991 Jan 1;2(4):339-50. doi: 10.3233/RNN-1991-245623.
The mechanisms underlying recovery of function following damage to the CNS, although suspected, are virtually unknown. After damage to the adult cat spinal cord, recovery of motor behavior depends on which systems have been interrupted and which remain intact. For example, following hemisection, overground (voluntary) and reflex locomotion recover and, although a normal kinematic pattern recovers, accurate placement of the limb during locomotion does not return to normal levels. This recovery is associated with lowering of thresholds for postural reflexes suggesting that increased afferent input may compensate for diminished descending control. In contrast, after unilateral loss of afferent input by lumbosacral deafferentation, (L1-S2 dorsal roots cut) overground locomotion recovers but a permanently abnormal kinematic pattern is used; reflex locomotion (bipedal locomotion on a treadmill) does not recover at all in the deafferented hindlimb. The specificity of the recovery suggests that increased input from descending pathways, which is required for overground but not reflex locomotion may compensate for loss of afferent input. Anatomical sequellae of these two lesion types have been examined. Studies after hemisection support the notion of a permanently increased dorsal root input as mapped by monoclonal antibody 'rat 102'. This is associated with a transient increase in GAP-43 labeling in the dorsal horn. In contrast, after deafferentation an increase is found in the descending serotonergic input to the deafferented side. These observations suggest that recovery of specific locomotor behavior can be used to predict compensatory changes in spared pathways. For the study of the effects of transplants, we have used complete spinal transections in newborn kittens with transplantation of E26 cat spinal cord into the transection site. The normal kitten develops overground locomotion beginning the end of the first week postnatal but reflex locomotion is delayed until the end of the second week. After transection on the first day of life, with or without a transplant, reflex locomotion begins precociously. Overground locomotion fails to develop in transection-only animals but does develop in animals with transection and transplant. This locomotion although clearly abnormal, shows postnatal development in terms of weight support and lateral stability. Furthermore, there is some indication of coordination between fore and hind limbs. These observations suggest that the transplants permit the development of some descending control although the anatomical correlates of this sparing/recovery of function are uncertain; the transplant rescues neurons caudal to the transection and also permits regeneration of some descending pathways into the transplant and caudally into host spinal cord.
中枢神经系统损伤后功能恢复的机制虽然可疑，但实际上却一无所知。成年猫脊髓损伤后，运动行为的恢复取决于哪些系统被中断，哪些系统仍然完整。例如，半横断后，地面（自愿）和反射运动恢复，尽管恢复了正常的运动模式，但肢体在运动中的准确位置无法恢复到正常水平。这种恢复与姿势反射阈值的降低有关，表明传入输入的增加可能补偿了下降控制的减少。相比之下，在腰骶去传入后（L1-S2 背根切断），单侧传入输入丧失后，地面运动恢复，但使用永久性异常运动模式；去传入后，反射运动（在跑步机上双足运动）完全不能恢复。这种恢复的特异性表明，对于地面运动而不是反射运动所需的来自下降通路的增加输入可能补偿传入输入的丧失。已经检查了这两种损伤类型的解剖后遗症。半横断后的研究支持永久性增加背根输入的概念，该概念由单克隆抗体“大鼠 102”映射。这与背角中 GAP-43 标记的短暂增加有关。相比之下，去传入后，去传入侧下降的 5-羟色胺能传入增加。这些观察结果表明，特定运动行为的恢复可以用于预测保留途径的代偿性变化。为了研究移植的影响，我们在新生小猫中使用完全脊髓横断，将 E26 猫脊髓移植到横断部位。正常小猫在出生后第一周结束时开始发展地面运动，但反射运动直到第二周结束时才开始。出生第一天进行横断后，无论是否进行移植，反射运动都会提前开始。只有横断的动物不能发展地面运动，但进行横断和移植的动物可以发展。这种运动虽然明显异常，但在体重支持和横向稳定性方面显示出了出生后的发育。此外，还有一些迹象表明前肢和后肢之间存在协调。这些观察结果表明，移植允许一些下行控制的发展，尽管这种功能的节省/恢复的解剖学相关性尚不确定；移植挽救了横断以下的神经元，并允许一些下行通路在移植中以及向宿主脊髓的尾部再生。
