INTEGRATION IN DESCENDING MOTOR PATHWAYS CONTROLLING THE FORELIMB IN THE CAT .17. AXONAL PROJECTION AND TERMINATION OF C3-C4 PROPRIOSPINAL NEURONS IN THE C6-TH1 SEGMENTS
INTEGRATION IN DESCENDING MOTOR PATHWAYS CONTROLLING THE FORELIMB IN THE CAT .17. AXONAL PROJECTION AND TERMINATION OF C3-C4 PROPRIOSPINAL NEURONS IN THE C6-TH1 SEGMENTS
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DOI：
10.1007/bf02423494
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发表时间：
1990-01-01
影响因子：
2
通讯作者：
TANTISIRA, B
中科院分区：
文献类型：
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作者：
ALSTERMARK, B;KUMMEL, H;TANTISIRA, B
用逆行激活C3-C4固有脊髓神经元的阈值标记法和轴突内注射辣根过氧化物酶两种方法研究了猫C6-Th1节段单个C3-C4固有脊髓神经元(PNS)的侧支和终末。C3-C4 PNS逆行激活的低阈值位于第IX层不同运动核团的同一水平和不同节段的区域、VII板的所有部位、VI板的外侧部以及VIII板的背侧部和腹侧部。轴突传导速度在终末尾侧明显减慢，而在终末吻区几乎不变。将HRP从C6-Th1区离子导入C5/C6侧索腹侧部分、外侧网状核(LRN)和C5/C6横断的皮质脊髓纤维(刺激对侧锥体)的神经元干轴突内。成功染色的干轴突重建，显示在第九层不同部分的假定运动神经元和第四至第八层的神经元间有终末的侧枝。这些发现证实了以前的结果，即从C3-C4三叉神经节向前肢运动神经元和Ia抑制性神经元的单突触投射。在第IX层运动神经元区域和第VII层Ia抑制性神经元区域，有三种类型：1)主要在第IX层终止(n=1)；2)主要终止在第IX和VII层(n=15)；然而，在某些情况下，同一干轴突发出的侧枝终止于第IX层的运动神经元或终止于第VII层的Ia抑制性神经元间。此外，当干轴突有终止于不同运动核团的侧枝时，仅有一些侧枝终止于推测的Ia抑制性神经元间。这一结果表明，C3-C4三叉神经节并不遵循严格的Ia相互神经支配模式。初步认为，神经支配的差异可能与多关节运动的类型有关，如前肢的触靶运动已被证明是由C3-C4三叉神经支配的。在VI、VIII板和VIII板不同部位的终末表明，C3-C4 PNS也投射到除运动神经元和Ia抑制性神经元外的其他类型神经元。将小麦胚胶凝集的辣根过氧化物酶(WGA-HRP)注射到C3和C4的VI-VII板层，可引起这些节段神经元轴突束的顺行标记。标记轴突主要分布在外侧索内，腹侧密度最高。这些轴突可以追踪到整个前肢节段，也可以追踪到LRN。
Collateralization and termination of single C3-C4 propriospinal neurones (PNs) have been studied in the C6-Th1 segments of the cat using two methods: threshold mapping for antidromic activation of C3-C4 PNs and intra-axonal injection of horseradish peroxidase. Low threshold points for antidromic activation of C3-C4 PNs were found in the region of different motor nuclei in lamina IX both at one level and at different segmental levels, in all parts of lamina VII, in the lateral part of lamina VI and in the dorsal and ventral parts of lamina VIII. Collaterals were found from C6 to Th1. A marked decrease of conduction velocity of the stem axon occurred in the caudal region of termination, while it was almost constant in the rostral region of termination. HRP was injected iontophoretically in c6-Th1 into stem axons of neurones, which were activated antidromically fom the ventral part of the lateral funiculus in C5/C6, from the lateral reticular nucleus (LRN) and monosynaptically from the corticospinal fibres (stimulated in the contralateral pyramid) which were transected in C5/C6. Reconstruction of successfully stained stem axons, revealed collaterals with terminals on presumed motoneurones in different parts of lamina IX and on interneurones in laminae IV-VIII. These findings confirm previous results which showed monosynaptic projections from C3-C4 PNs to forelimb motoneurones and Ia inhibitory interneurones. With respect to temrination in the region of the motoneurones in lamina IX and in the region of Ia inhibitory interneurones in lamina VII, three patterns were found: 1) termination mainly in lamina IX (n = 1) 2) termination in lamina IX and VII (n = 15) and 3) termination mainly in lamina VII (n = 2). However, in some cases the same stem axon gave off collaterals which terminated either on motoneurones in lamina IX or on presumed Ia inhibitory interneurones in lamina VII. Furthermore, when the stem axons had collaterals which terminated in different motor nuclei only some of these collaterals had additional terminations on presumed Ia inhibitory interneurones. This result suggest that C3-C4 PNs do not follow a strict Ia pattern of reciprocal innervation. It is tentatively proposed that the difference of innervation may be related to the type of multi-joint movement, such as target-reaching with the forelimb, which has been shown to be controlled by the C3-C4 PNs. Termination in laminae VI, VIII and different parts of lamina VII indicates that C3-C4 PNs also project to other types of neurones than motoneurones and Ia inhibitory interneurones. Injection of wheat germ agglutinated horseradish peroxidase (WGA-HRP) laterally in laminae VI-VII in C3 and C4 caused anterograde labelling of axonal bundles from neurones in these segments. Labelled axons were found mainly in the lateral funiculus with the highest density in the ventral part. These axons could be traced throughout the forelimb segments and also to the LRN.