PROPERTIES OF CENTRAL AXONS AT PERIPHERAL TARGETS

现在已经确定，尽管中枢神经纤维将 在成年哺乳动物体内不能长距离伸长 中枢神经系统(CNS)，它们很容易在 神经插入中枢神经系统的周围环境。尽管 具有这种特性的神经元的种类，到目前为止还没有 再生轴突是否由其诱导的报告 开发终端的外周环境和靶器官 能够进行感觉或运动转导的专门化。如果是这样的话 受体形成后，周围神经移植物可能会 瘫痪麻木肢体功能恢复的价值 由脊髓损伤所致。值得注意的是，我们的初步实验 已经证实有效的突触是在 中枢神经纤维沿途再生的失神经骨骼肌 腹根重新生于侧柱内。 中枢神经纤维将通过再植从脊髓中引出 腹根和背根对失神经骨骼的再神经支配 肌肉或失去神经的皮肤。腹根和背根将是 重新植入腹外侧柱和背侧柱内 分别在它们的正常连接处附近，或通过移植物， 到达假定的脊柱损伤位置上方的位置 电源线。4-8个月后，将对大鼠进行生理学评估 并在组织学上确定a)运动或感觉 终端已经形成，b)所涉及的光纤的身份， 以及c)再生神经元是否有助于 运动或感觉功能。成功的运动神经再生将是 评估，部分是通过确定是否存在收缩 直接刺激再植者的适当肌肉 前根，并在间接(突触)激活 运动神经元。肌肉神经再支配的恢复也将是 使用肌电记录进行连续监测。成功的感官 神经再支配将在一定程度上通过映射感觉来确定。 从重新种植的根上梳理出来的单独的纤维，并被 确定由感官引起的中枢反应的存在 刺激。另一项实验将检验轴突是否 损伤是产生轴突的先决条件。

It is now well established that although central nerve fibers will not elongate over long distances within the adult mammalian central nervous system (CNS), they readily do so within the peripheral environment of nerves inserted into the CNS. Despite the variety of neurons with this property, there has so far been no report of whether the regenerating axons are induced by their peripheral environment and target organs to develop terminal specializations capable of sensory or motor transduction. If such receptors are formed, then peripheral nerve grafts may be of value in restoring function to limbs rendered paralysed and numb by spinal cord injury. Significantly, our preliminary experiments have established that effective synapses are formed on denervated skeletal muscle by central fibers regenerating along ventral roots replanted into the lateral column. Central nerve fibers will be led from the spinal cord via replanted ventral and dorsal roots to reinnervate either denervated skeletal muscle or denervated skin. The ventral and dorsal roots will be replanted into the ventro-lateral and dorso-lateral columns respectively, either near to their normal junction or, via a graft, to a site above the supposed location of an injury to the spinal cord. After 4-8 months the rats will be assessed physiologically and histologically to determine a) whether motor or sensory terminals have formed, b) the identities of the fibers involved, and c) whether the regenerating neurons contribute to useful motor or sensory function. Successful motor reinnervation will be assessed, in part by determining the presence of contractions of the appropriate muscles upon direct stimulation of the replanted ventral root, and upon indirect (synaptic) activation of motoneurons. The return of muscle reinnervation will also be monitored serially using EMG recordings. Successful sensory reinnervation will be determined, in part, by mapping the sensory fields of individual fibers teased from the replanted roots, and by determining the presence of central responses evoked by sensory stimulation. Another experiment will examine whether axonal damage is a prerequisite to neurite production.