Koerber H Richard, Mirnics Karoly, Lawson Jeffrey J
Department of Neurobiology, University of Pittsburgh, School of Medicine, PA 15261, USA.
Exp Neurol. 2006 Aug;200(2):468-79. doi: 10.1016/j.expneurol.2006.03.003. Epub 2006 May 11.
Peripherally regenerated fibers were impaled in the dorsal columns. Each impaled fiber's adequate stimulus was determined and the fiber was activated by passing brief (200 ms) current pulses through the microelectrode. Cord dorsum potentials (CDPs) elicited by fiber stimulation were recorded at 8 sites, and then the fiber was injected with Neurobiotin (NB). In the same preparations, dorsal horn cells were impaled and their receptive fields (RFs) mapped; areas of skin from which the most vigorous responses were elicited were noted. Needle electrodes inserted into these cutaneous "hot spots" were used to electrically activate minimal numbers of peripherally regenerated fibers while simultaneously recording the resulting CDPs and any intracellular EPSPs. This allowed determination of connectivity between regenerated fibers and dorsal horn cells with overlapping RFs. In agreement with findings in intact animals, NB revealed long-ranging collaterals which were not seen using intraaxonally injected horseradish peroxidase (HRP). Although there was no qualitative difference in their morphology compared to those seen in controls, the correlation between spatial distribution of boutons and amplitudes of the monosynaptic CDPs of peripherally regenerated fibers revealed significant shifts in the functional efficacy of many central connections. Transcutaneous electrical stimulation revealed a significantly higher incidence of connectivity between regenerated fibers and cells with overlapping RFs at 9-12 months (86%) than at 5-6 months (34%). Although there was no obvious anatomical reorganization of afferent projections in the dorsal horn, the observed functional changes with time following transection show the formation of new functional central connections.
在外周再生的纤维被刺入背柱。确定每根被刺入纤维的适宜刺激，并通过微电极施加短暂（200毫秒）电流脉冲来激活该纤维。在8个位点记录纤维刺激引发的脊髓背电位（CDP），然后向纤维内注入神经生物素（NB）。在相同的标本中，刺入背角细胞并绘制其感受野（RF）；记录引发最强烈反应的皮肤区域。将针电极插入这些皮肤“热点”，用于电激活最少数量的外周再生纤维，同时记录产生的CDP和任何细胞内兴奋性突触后电位（EPSP）。这使得能够确定再生纤维与具有重叠RF的背角细胞之间的连接性。与完整动物的研究结果一致，NB显示出使用轴突内注射辣根过氧化物酶（HRP）未观察到的长距离侧支。尽管与对照组相比，它们的形态没有质的差异，但外周再生纤维的突触小体空间分布与单突触CDP振幅之间的相关性揭示了许多中枢连接功能效能的显著变化。经皮电刺激显示，与5 - 6个月（34%）相比，9 - 12个月时再生纤维与具有重叠RF的细胞之间的连接发生率显著更高（86%）。尽管背角传入投射没有明显的解剖学重组，但横断后随时间观察到的功能变化表明形成了新的功能性中枢连接。
