Adv Anat Embryol Cel
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Adv Anat Embryol Cel · Jan 1997
ReviewThe projections to the spinal cord of the rat during development: a timetable of descent.
In order to establish a timetable for the developmental descent of supraspinal descending projections in the rat, a retrograde neuronal tracer was injected into the spinal cord of rat fetuses and neonates both at different gestational ages and at different levels of the spinal cord. From the results of these experiments a position interval could be deduced for the leading descending fibers of each spinal-projecting nucleus at each age studied. The chronological series of position intervals of each supraspinal descending projection (the descent pattern) depicts the descent of its fiber front during development and allows for easy comparison between the various projections. ⋯ These results confirm that the generation sequence of the source nuclei is not a prime determinant of descent sequence along the spinal cord. The distance between the source nucleus and the entrance to the target seems of influence only in the most extreme cases (diencephalic source nuclei and the cerebral cortex). Descent velocity of the fiber fronts is not equal between different sources, nor is the descent velocity of specific fiber fronts constant over time. (ABSTRACT TRUNCATED)