Goldberger M E, Murray M
Brain Res. 1982 Jun 10;241(2):227-39. doi: 10.1016/0006-8993(82)91059-9.
Degeneration methods were used to study the dorsal root and descending projections after chronic partial denervation of adult cat spinal cord. Conventional mapping methods were used, supplemented in some cases by densitometric measurements of the amounts of degeneration present. The amount of shrinkage of spinal gray matter in some sections was estimated by planimetric measurement. Two preparations were used: (1) partial unilateral rhizotomy in which all dorsal roots caudal to T4 were cut except L6 (spared root preparation); (2) complete unilateral deafferentation. The projection of L6 dorsal roots was examined in spared root preparations. T13 dorsal root projections were examined in deafferented preparations in which T13 was the lowest remaining root. The projection of descending systems was mapped in spared root and deafferented preparations. The spared root displayed an increased projection in the lateral portion of the dorsal horn, in the zona intermedia, Clarke's nucleus and in the base and reticular zone of nucleus gracilis. The lowest remaining root (T13) increased its projection to laminae VII and VIII and to the base and reticular zone of nucleus gracilis. In all cases, when an increased projection resulted from prior denervation, the increase never exceeded the boundaries of the normal projection. No sprouting was observed in those regions with the strictest topographical organization, the cell nests of nucleus gracilis or lamina IX of the spinal cord, even though these regions were partially denervated by the chronic lesions. Descending projections were increased on the experimental side of deafferented preparations12 but not of spared root preparations, suggesting that the presence of the spared root may prevent sprouting by descending systems. Because measurements of gray matter indicated that maximal sprouting occurred in segments showing least shrinkage (sprouting of L6 spared root into L6 segment), in this case shrinkage cannot account for the increased density of degeneration. These results suggest that certain conditions are important for the regulation of sprouting in the adult CNS. Firstly, sprouting is limited by a requirement for proximity and/or overlap. Secondly, the strictness of topographical localization within a particular region may limit the likelihood of sprouting into that region. Finally, a competitive or hierarchical relationship among the remaining systems may modify the capacity of a particular system to sprout.
采用变性方法研究成年猫脊髓慢性部分去神经支配后的背根和下行投射。使用传统的绘图方法，在某些情况下辅以对变性量的密度测量。通过平面测量估计一些切片中脊髓灰质的收缩量。使用了两种制备方法：（1）部分单侧神经根切断术，其中除L6外，T4以下的所有背根均被切断（保留根制备）；（2）完全单侧传入神经切断术。在保留根制备中检查L6背根的投射。在去传入神经制备中检查T13背根的投射，其中T13是剩余的最低神经根。在保留根和去传入神经制备中绘制下行系统的投射。保留根在背角外侧部分、中间带、克拉克核以及薄束核基部和网状带显示投射增加。剩余的最低神经根（T13）增加了其向VII层和VIII层以及薄束核基部和网状带的投射。在所有情况下，当先前的去神经支配导致投射增加时，增加从未超过正常投射的边界。在地形组织最严格的区域，即薄束核细胞巢或脊髓IX层，即使这些区域因慢性损伤而部分去神经支配，也未观察到发芽。在去传入神经制备的实验侧，下行投射增加，但在保留根制备中未增加，这表明保留根的存在可能会阻止下行系统发芽。因为灰质测量表明最大发芽发生在收缩最小的节段（L6保留根向L6节段发芽），在这种情况下，收缩不能解释变性密度的增加。这些结果表明，某些条件对成年中枢神经系统发芽的调节很重要。首先，发芽受到接近度和/或重叠要求的限制。其次，特定区域内地形定位的严格性可能会限制向该区域发芽的可能性。最后，如果剩余系统之间存在竞争或层级关系，可能会改变特定系统发芽的能力。
