Benítez-Temiño Beatriz, De La Cruz Rosa R, Pastor Angel M
Departamento de Fisiología y Biología Animal, Universidad de Sevilla, 41012-Seville, Spain.
J Comp Neurol. 2002 Mar 18;444(4):324-44. doi: 10.1002/cne.10147.
Axotomy produces changes in the electrical properties of neurons and in their synaptic inputs, leading to alterations in firing pattern. We have considered the possibility that these changes occur as a result of the target deprivation induced by the lesion. Thus, we have provided a novel target to axotomized central neurons by grafting embryonic tissue at the lesion site to study the target dependence of discharge characteristics. The extracellular single-unit electrical activity of abducens internuclear neurons was recorded in the alert behaving cat in control, after axotomy, and after axotomy plus the implantation of cerebellar primordium. As recently characterized (de la Cruz et al. [2000] J. Comp. Neurol. 427:391-404), firing alterations induced by axotomy included an overall decrease in firing rate and a loss of eye-related signals, i.e., eye position and velocity neuronal sensitivities, that do not resume to normality with time. The grafting of a novel target to the injured abducens internuclear neurons restored the normal firing and sensitivities as recorded in the majority of units. To study the reinnervation of the implant, we performed anterograde labeling with biocytin combined with electron microscopy visualization. Axons of abducens internuclear neurons grew into the transplant sprouting into granule cell and molecular layers, as characterized by the immunostaining for gamma-aminobutyric acid and calbindin D-28k. Ultrastructural examination of labeled axons and boutons revealed the establishment of synaptic contacts, mainly axodendritic, with different cell types of the grafted cerebellar cortex. Therefore, these data indicate that axotomized central neurons resume to normal firing after the reinnervation of a novel target.
轴突切断术会导致神经元电特性及其突触输入发生变化，进而引起放电模式改变。我们曾考虑过这些变化是由损伤诱导的靶剥夺所致。因此，我们通过在损伤部位移植胚胎组织，为轴突切断的中枢神经元提供了一个新的靶标，以研究放电特征的靶依赖性。在清醒的行为猫中，记录了展神经核间神经元在对照状态、轴突切断术后以及轴突切断术加小脑原基植入后的细胞外单单位电活动。如最近所描述的（德拉·克鲁兹等人[2000]《比较神经学杂志》427:391 - 404），轴突切断术引起的放电改变包括放电率总体下降以及与眼相关信号的丧失，即眼位和速度神经元敏感性，且这些不会随时间恢复正常。将新靶标移植到受损的展神经核间神经元后，大多数单位记录到的放电和敏感性恢复了正常。为了研究植入物的再支配情况，我们结合电子显微镜可视化，用生物胞素进行了顺行标记。展神经核间神经元的轴突生长进入移植组织，向颗粒细胞层和分子层发芽，这通过γ - 氨基丁酸和钙结合蛋白D - 28k的免疫染色得以表征。对标记轴突和终扣的超微结构检查显示，与移植小脑皮质的不同细胞类型建立了主要为轴 - 树突型的突触联系。因此，这些数据表明，轴突切断的中枢神经元在获得新靶标的再支配后恢复了正常放电。
