van der Linden J A, ten Donkelaar H J
Department of Anatomy and Embryology, University of Nijmegen, The Netherlands.
Anat Embryol (Berl). 1987;176(4):431-9. doi: 10.1007/BF00310084.
The development of cerebellar afferents has been studied in the clawed toad, Xenopus laevis, from stage 46 to 64, with the horseradish peroxidase retrograde tracer technique. Already in stage 48 tadpoles, i.e. before the formation of the limbs, a distinct set of cerebellar afferents was found. Vestibulocerebellar (mainly arising bilaterally in the nucleus vestibularis caudalis) and contralateral olivo-cerebellar projections dominate. Secondary trigeminocerebellar (from the descending nucleus of the trigeminal nerve) and reticulocerebellar connections were also found. At stage 50, spinocerebellar projections appear originating from cervical and lower thoracic/upper lumbar levels. The cells of origin of the spinocerebellar projection can be roughly divided in two neuronal types: ipsilaterally projecting large cells, which show a marked resemblance to primary motoneurones ('spinal border cells') and smaller contralaterally projecting neurons. Primary spinocerebellar projections from spinal ganglion cells could not be demonstrated. At stage 50, a possible anuran homologue of the mammalian nucleus prepositus hypoglossi was found to project to the cerebellum. In only one of the experiments labeled neurons were found in the contralateral mesencephalic tegmentum. At none of the studied stages a raphecerebellar projection could be demonstrated. It appears that already early in cerebellar development, before the formation of the limbs, most of the cerebellar afferents as found in adult Xenopus laevis are present.
利用辣根过氧化物酶逆行示踪技术，对非洲爪蟾（非洲爪蟾）从第46期到64期的小脑传入神经发育进行了研究。在第48期蝌蚪中，即在四肢形成之前，就发现了一组独特的小脑传入神经。前庭小脑（主要双侧起源于尾侧前庭核）和对侧橄榄小脑投射占主导地位。还发现了二级三叉小脑（来自三叉神经降核）和网状小脑连接。在第50期，脊髓小脑投射出现，起源于颈部和胸下部/腰上部水平。脊髓小脑投射的起源细胞大致可分为两种神经元类型：同侧投射的大细胞，与初级运动神经元（“脊髓边界细胞”）非常相似，以及对侧投射的较小神经元。未发现脊髓神经节细胞的初级脊髓小脑投射。在第50期，发现了哺乳动物舌下前置核可能的无尾类同源物投射到小脑。在仅有的一个实验中，在对侧中脑被盖中发现了标记神经元。在所有研究阶段均未发现缝际小脑投射。似乎在小脑发育早期，即在四肢形成之前，成年非洲爪蟾中发现的大多数小脑传入神经就已存在。
