Zhang Yongquan, Luo Yuanjun, Sasamura Kazuma, Sugihara Izumi
Department of Systems Neurophysiology, Graduate School, Tokyo Medical and Dental University, Tokyo, Japan.
Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan.
J Comp Neurol. 2021 Dec;529(18):3893-3921. doi: 10.1002/cne.25223. Epub 2021 Aug 17.
Among the spinocerebellar projections vital for sensorimotor coordination of limbs and the trunk, the morphology of spinocerebellar axons originating from the lumbar cord has not been well characterized compared to those from thoracic and sacral cords. We reconstructed 26 single spinocerebellar axons labeled by biotinylated dextran injections into the gray matter of the lumbar spinal cord in mice. Axon terminals were mapped with the zebrin pattern of the cerebellar cortex. Reconstructed axons were primarily classified into ipsilaterally and contralaterally ascending axons, arising mainly from the dorsal and ventral horns, respectively. The majority of ipsilateral and contralateral axons took the dorsal-medullary and ventral-pontine pathways, respectively. The axons of both groups terminated mainly in the vermal and medial paravermal areas of lobules II-V and VIII-IXa, often bilaterally but predominantly ipsilateral to the axonal origin, with a weak preference to particular portions of zebrin stripes. The ipsilateral axons originating from the medial dorsal horn in the upper lumbar cord (n = 3) had abundant (43-147) mossy fiber terminals and no medullary collaterals. The ipsilateral axons originating from the lateral dorsal horn in the lower lumbar cord (n = 9) and the contralateral axons (n = 14) showed remarkable morphology variations. The number of their mossy fiber terminals varied from 2 to 172. Their collaterals, observed in 17 axons out of 23, terminated mainly in the medial cerebellar nucleus, nucleus X, and lateral reticular nucleus in various degrees. The results indicated that the lumbar spinocerebellar projection contains highly heterogeneous axonal populations regarding their pathway, branching, and termination patterns.
在对肢体和躯干的感觉运动协调至关重要的脊髓小脑投射中，与来自胸段和骶段脊髓的轴突相比，源自腰段脊髓的脊髓小脑轴突的形态尚未得到充分表征。我们重建了26条通过向小鼠腰段脊髓灰质注射生物素化葡聚糖标记的单条脊髓小脑轴突。轴突终末通过小脑皮质的zebrin模式进行定位。重建的轴突主要分为同侧和对侧上行轴突，分别主要起源于背角和腹角。大多数同侧和对侧轴突分别走背侧延髓和腹侧脑桥通路。两组轴突主要终止于小叶II - V和VIII - IXa的蚓部和内侧旁蚓部区域，通常是双侧的，但主要是轴突起源的同侧，对zebrin条纹的特定部分有较弱的偏好。源自腰段脊髓上部内侧背角的同侧轴突（n = 3）有丰富的（43 - 147个）苔藓纤维终末且无延髓侧支。源自腰段脊髓下部外侧背角的同侧轴突（n = 9）和对侧轴突（n = 14）表现出显著的形态变异。它们的苔藓纤维终末数量从2到172不等。在23条轴突中的17条中观察到的它们的侧支，不同程度地主要终止于内侧小脑核、X核和外侧网状核。结果表明，腰段脊髓小脑投射在其通路、分支和终末模式方面包含高度异质性的轴突群体。
