Koerber H R, Mirnics K, Brown P B, Mendell L M
Department of Neurobiology, University of Pittsburgh, Pennsylvania 15261.
J Neurosci. 1994 Jun;14(6):3655-71. doi: 10.1523/JNEUROSCI.14-06-03655.1994.
A combination of neuroanatomical and electrophysiological techniques was used to study the effects of peripheral axotomy and regeneration of primary afferents on their central projections in the spinal cord. Individual regenerated afferent fibers were impaled with HRP-filled electrodes in the dorsal columns of alpha-chloralose-anesthetized cats and activated by current pulses delivered via the intracellular electrode. The resulting cord dorsum potentials (CDPs) were recorded at four rostrocaudal locations and HRP was iontophoretically injected into the fiber. Central distributions of boutons and CDPs were compared with peripheral receptor type to determine the accuracy of peripheral regeneration and the effects of central-peripheral mismatches. Reconstruction of the central projections of 13 individual afferents for which the adequate stimulus and CDPs had been recorded revealed many abnormalities. For example, unlike controls, four group I and II afferents with central projections typical of proprioceptors (concentrated in laminae V, VI, and VII) innervating either cutaneous or noncutaneous targets evoked measurable CDPs. Three other group II or A beta afferents innervating low-threshold mechanoreceptors with central terminations confined to the dorsal horn exhibited extensive collateralization in laminae I and II in addition to large numbers of terminals in laminae III-IV. These fibers activated central networks whose adaptation behavior was identical to those evoked by high-threshold mechanoreceptive afferents in controls. These results suggest that primary afferents and their central connections are capable of significant modifications following axotomy and regeneration. In addition, the anatomical studies indicate some reorganization in the laminar distribution of boutons as well as in bouton size.
采用神经解剖学和电生理学技术相结合的方法，研究外周轴突切断和初级传入神经再生对其在脊髓中中枢投射的影响。在α-氯醛糖麻醉的猫的背柱中，用充满辣根过氧化物酶（HRP）的电极刺入单个再生的传入纤维，并通过细胞内电极施加电流脉冲来激活它们。在四个前后位置记录由此产生的脊髓背电位（CDP），并将HRP离子电渗注入纤维中。将终扣和CDP的中枢分布与外周感受器类型进行比较，以确定外周再生的准确性以及中枢-外周不匹配的影响。对13个已记录到适宜刺激和CDP的单个传入神经的中枢投射进行重建，发现了许多异常情况。例如，与对照组不同，四条支配皮肤或非皮肤靶标的I类和II类传入神经，其具有本体感受器典型的中枢投射（集中在V、VI和VII层），可诱发可测量的CDP。另外三条支配低阈值机械感受器的II类或Aβ传入神经，其中枢终末局限于背角，除了在III-IV层有大量终末外，在I和II层还表现出广泛的侧支化。这些纤维激活的中枢网络，其适应行为与对照组中高阈值机械感受性传入神经诱发的行为相同。这些结果表明，初级传入神经及其中枢连接在轴突切断和再生后能够发生显著改变。此外，解剖学研究表明，终扣的层状分布以及终扣大小都有一些重组。
