Analysis of individual Ia-afferent EPSPs in a homonymous motoneuron pool with respect to muscle topography.
Analysis of individual Ia-afferent EPSPs in a homonymous motoneuron pool with respect to muscle topography.
复制标题
对同名运动神经元池中的单个 Ia 传入 EPSP 进行肌肉地形分析。
DOI：
10.1152/jn.1984.51.1.64
复制
发表时间：
1984
影响因子：
2.5
通讯作者：
Binder,MD
中科院分区：
文献类型：
--
作者：
Lucas,SM;Cope,TC;Binder,MD
尖峰触发的平均技术（26）被用来确定从内侧腓肠肌（MG）Ia传入纤维到同侧运动神经元的突触输入是否是通过投射频率、兴奋性突触后电位（EPSP）振幅或两种因素的组合的差异进行“地形加权”（22）的。运动神经元分为“相同分支”或“其他分支”，这取决于是否IA传入纤维和运动轴突包含在相同或不同的肌内神经分支。没有发现在同一分支和其他分支运动神经元（分别为95%和94%）的投影频率的IA传入。同一运动神经元分支组的平均EPSP振幅（92 +/- 8（SE）microV; n = V; n = 97）大于另一分支组（77 +/- 7 microV; n = 79）。这种差异在高基强度（大于或等于10 nA）运动神经元中最为显著，同一分支组的平均EPSP振幅为82 +/- 12 microV（n = 48），而另一个分支组为52 +/- 5 microV（n = 37）。在60例病例中，可以比较同一运动神经元内同一分支传入和另一分支传入产生的EPSP。同一分支传入产生较大的EPSP者占73%（44/60）。此外，同一分支与其他分支EPSP振幅的平均比值为1.7，这既具有统计学显著性，又与我们之前对聚合EPSP的研究结果一致（22）。同一分支组与另一分支组EPSP的平均上升时间和半宽无显著差异。此外，两组之间的上升时间或半宽度没有显着差异是明显的运动神经元分离时，根据其基强度值。这表明，IA传入和运动轴突的肌内神经分支的隔离并没有反映在Ia终端的位置上的运动神经元体细胞表面和其他因素必须占观察到的EPSP振幅差异。我们的数据表明，地形加权homoproteia传入输入猫MG运动神经元介导的梯度EPSP振幅，而不是由梯度Ia连接，也表明，效果是最突出的高基强度运动神经元。
The spike-triggered averaging technique (26) was used to determine whether the synaptic input from medial gastrocnemius (MG) Ia-afferent fibers to homonymous motoneurons is "topographically weighted" (22) by means of differences in projection frequency, excitatory postsynaptic potential (EPSP) amplitude, or a combination of both factors. Motoneurons were classified as either "same branch" or "other branch," depending on whether a Ia-afferent fiber and motor axon were contained in the same or different intramuscular nerve branches. No difference was found in the projection frequency of Ia-afferents to the same branch and other branch motoneurons (95 versus 94%, respectively). The mean EPSP amplitude was larger in the same branch group of motoneurons (92 +/- 8 (SE) microV; n = V; n = 97) than in the other branch group (77 +/- 7 microV; n = 79). This difference was most striking in high-rheobase (greater than or equal to 10 nA) motoneurons, for which the mean EPSP amplitude in the same branch group was 82 +/- 12 microV (n = 48), whereas that in the other branch group was 52 +/- 5 microV (n = 37). In 60 cases it was possible to compare the EPSPs produced by a same branch afferent and an other branch afferent in the same motoneuron. The same branch afferent produced the larger EPSP in 73% (44/60) of the cases. Moreover, the mean ratio of the same branch to the other branch EPSP amplitudes was 1.7, which was both statistically significant and consistent with analogous results from our preceding study of aggregate EPSPs (22). Mean rise times and half-widths of EPSPs in the same branch group were not significantly different from those in the other branch group. Furthermore, no significant differences in rise times or half-widths between the two groups were evident when motoneurons were segregated according to their rheobase values. This suggests that the segregation of Ia-afferent and motor axons across the intramuscular nerve branches is not reflected in the locations of Ia terminals on the motoneuron somadendritic surface and that other factors must account for observed EPSP amplitude differences. Our data suggest that the topographic weighting of homonymous Ia-afferent input to cat MG motoneurons is mediated by a gradient of EPSP amplitude rather than by a gradient of Ia connectivity and also suggest that the effect is most prominent in high-rheobase motoneurons.