INTEGRATION IN DESCENDING MOTOR PATHWAYS CONTROLLING THE FORELIMB IN THE CAT .8. ASCENDING PROJECTION TO THE LATERAL RETICULAR NUCLEUS FROM C3-C4 PROPRIOSPINAL NEURONS ALSO PROJECTING TO FORELIMB MOTO-NEURONS
INTEGRATION IN DESCENDING MOTOR PATHWAYS CONTROLLING THE FORELIMB IN THE CAT .8. ASCENDING PROJECTION TO THE LATERAL RETICULAR NUCLEUS FROM C3-C4 PROPRIOSPINAL NEURONS ALSO PROJECTING TO FORELIMB MOTO-NEURONS
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DOI：
10.1007/bf00237495
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发表时间：
1981-01-01
影响因子：
2
通讯作者：
SYBIRSKA, E
中科院分区：
文献类型：
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作者：
ALSTERMARK, B;LINDSTROM, S;SYBIRSKA, E
本文分析了C3-C4固有脊髓神经元(PN)向外侧网状核(LRN)的上行投射，这些神经元由几个高级运动中枢单突触激活并向尾侧投射，其中一些直接投射到前肢运动神经元。C3-C4节段的细胞可从C7的侧索和同侧LRN逆行激活，进行细胞外和细胞内记录。向LRN的上行投射在84%终止于Th9的PN中可见，但在投射至Th9以外的PN中最多占11%。LRN内及周围的阈值标测显示，上行侧支的干轴突从背内侧至其尾侧部分进入核内，并沿整个核吻尾部在不同的水平终止。终末不限于前肢区(A区)，也可见于LRN的腹侧部分。升支传导速度普遍低于降支(平均值分别为26和44m/S)。PN投射至Th9以上时传导速度较高(平均值101m/S)。刺激LRN在前肢运动神经元中诱发大的单突触EPSP[兴奋性突触后电位]，这与C3-C4PN的双重投射是一致的。这些EPSP起源于C3-C4PN侧支的上行和终止区。它们的潜伏期和时程与预期的由C3-C4PN的分支轴突介导的EPSP相同。它们显然是由上升神经元的反向激活产生的，这些神经元也投射到前肢运动神经元。来自LRN的单突触EPSP存在于所有运动核团中，但在运动神经元到屈肘肌中大于在伸肘肌中(平均值分别为4.5和2.9 mV)。后超极化持续时间的快慢运动神经元从LRN收到EPSP，即使锥体抽动在前者引起兴奋，在后者引起抑制。双刺激LRN可显著增强EPSP的频率效应。刺激LRN可明显促进Ia抑制通路向运动神经元的传递。LRN的有效区域、阈值强度和时程与运动神经元的单突触EPSP相同。Ia抑制中间神经元接受C3-C4 Pn的直接投射，推测这些Pn也有LRN的上行侧支，LRN逆行介导对Ia抑制中间神经元的单突触兴奋。上升侧支可能是大脑控制C3-C4PN控制前肢运动的内在反馈中的一个环节。这种上升信息模式是前肢运动神经元和Ia抑制中间神经元活动的一面镜子，本文讨论了与其他上升系统中发出内在脊髓活动信号的更复杂信息的关系。
An analysis was made of the ascending projection to the lateral reticular nucleus (LRN) from the previously described C3-C4 propriospinal neurons (PN) which are monosynaptically activated from several higher motor centers and project caudally, some of them directly to forelimb motoneurons. Extra- and intracellular recording was made from cells in the C3-C4 segments which could be antidromically activated, both from the lateral funicle in C7 and from the ipsilateral LRN. The ascending projection to LRN was found in 84% of the PN terminating rostral to Th9 but at the most in 11% of the PN projecting beyond Th9. Threshold mapping in and around the LRN showed that the stem axons of the ascending collaterals enter the nucleus from a position dorsomedial to its caudal part and terminate at different levels, along the entire rostrocaudal extent of the nucleus. Termination was not restricted to the forelimb region (the A-zone) but was found also in the ventral part of the LRN. The conduction velocity was generally slower in the ascending than in the descending branch (mean values 26 and 44 m/s). The conduction velocity was higher in the PN projecting beyond Th9 (mean value 101 m/s). Stimulation in the LRN evoked large monosynaptic EPSP [excitatory postsynaptic potential] in forelimb motoneurons as would be expected from the double projection of C3-C4 PN. These EPSP are elicited from the regions where the collaterals from C3-C4 PN ascend and terminate. Their latency and time course are those expected for EPSP mediated by the bifurcating axons of C3-C4 PN. They are apparently produced by antidromic activation of ascending neurons also projecting to forelimb motoneurons. The monosynaptic EPSP from the LRN were found in all motor nuclei tested but were larger in motoneurons to elbow flexors than to elbow extensors (mean values 4.5 and 2.9 mV). Motoneurons classified as fast or slow from the duration of the afterhyperpolarization received EPSP from the LRN, even if pyramidal volleys evoked excitation in the former and inhibition in the latter. Double stimuli in the LRN revealed considerable frequency potentiation of the EPSP. Stimulation in the LRN gives marked facilitation of transmission in the reciprocal Ia inhibitory pathway to motoneurons. The effective LRN region, threshold strength and time course is the same as for the monosynaptic EPSP in motoneurons. The Ia inhibitory interneurons receive a direct projection from C3-C4 PN, and it is postulated that these PN also have an ascending collateral to the LRN which antidromically mediate monosynaptic excitation to the Ia inhibitory interneurons. The ascending collaterals may be a link in an intrinsic feed-back by which the brain controls how the C3-C4 PN govern forelimb movements. This mode of ascending information, a mirror of the activity reaching forelimb motoneurons and Ia inhibitory interneurons, is discussed in relation to the more complex information in other ascending systems signalling intrinsic spinal activity.