Stelzner D J, Weber E D, Prendergast J
Brain Res. 1979 Aug 31;172(3):407-26. doi: 10.1016/0006-8993(79)90575-4.
Transecting the thoracic spinal cord of the rat has markedly different effects on behavioral responses of the hindlimbs if the lesion is made at the neonatal or weanling stage of development. The present investigation tested the possibility that the behavioral differences were related to a difference in the distribution or density of dorsal root connections in the lumbosacral spinal cord. In order to use each animal as its own control the distribution and density of dorsal root axons was compared on the two sides of the L5-S1 segments of the lumbosacral spinal cord in adult rats given a mid-thoracic spinal hemisection at the neonatal or weanling stage of development. Comparing the experimental (initially hemisected side) and control sides of the cord, we found no evidence for a change in the distribution of dorsal root axons. The distribution of Fink-Heimer stained degeneration 4--6 days after bilateral spinal root section was virtually identical on the two sides of the cord from animals hemisected at either stage. However, in rats spinally hemisected at the neonatal stage (n = 8), a significantly greater density of dorsal root degeneration was found within the intermediate nucleus of Cajal (INC) on the experimental side using coded material and a blind analysis. No difference in the density of dorsal root degeneration was detected in the group of rats spinally hemisected at the weanling stage (n = 6). Controls indicated that the increased density of degeneration was not due to compression resulting from shrinkage of the INC or to degeneration remaining from the initial hemisection. We conclude that the increased amount of argyrophilia within the INC of neonatally hemisected rats is due to an increased density of dorsal root axons in this zone. This result supports the hypothesis that the behavioral differences found when comparing animals transected at the neonatal or weanling stages of development are related to an increased number of dorsal root connections within the lumbosacral spinal cord.
如果在新生期或断奶期对大鼠进行胸段脊髓横断，对后肢行为反应会产生明显不同的影响。本研究检验了行为差异是否与腰骶部脊髓背根连接分布或密度差异有关的可能性。为了将每只动物作为自身对照，在新生期或断奶期进行胸段脊髓半横断的成年大鼠中，比较了腰骶部脊髓L5-S1节段两侧背根轴突的分布和密度。比较脊髓的实验侧（最初半横断侧）和对照侧，我们没有发现背根轴突分布发生变化的证据。在两个阶段进行半横断的动物中，双侧脊髓神经根切断后4-6天，Fink-Heimer染色的变性分布在脊髓两侧几乎相同。然而，在新生期脊髓半横断的大鼠（n = 8）中，使用编码材料和盲法分析发现，实验侧Cajal中间核（INC）内背根变性密度显著更高。在断奶期脊髓半横断的大鼠组（n = 6）中，未检测到背根变性密度的差异。对照表明，变性密度增加不是由于INC萎缩导致的压迫，也不是由于最初半横断残留的变性。我们得出结论，新生期半横断大鼠INC内嗜银性增加是由于该区域背根轴突密度增加。这一结果支持了以下假设：在比较新生期或断奶期横断的动物时发现的行为差异与腰骶部脊髓内背根连接数量增加有关。
