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Abstract
This study was undertaken to elucidate ultrastructurally and quantitatively the development
of the corticospinal tract (CST) axons of mouse at the intumescence level of the cervical
cord. An anterograde HRP study showed that the CST was located at the ventral one-third
of the dorsal funiculus, and a few HRP-positive fibers were noted at the medialmost
part of the ipsilateral anterior funiculus. Ultrastructurally, the CST was composed
of unmyelinated axons, growth cones and a few degenerating axons until postnatal day
10 (P10), then the axons in CST gradually increased in size. The number of axons constituting
the right CST was calculated at different days of age. The total numbers of axons
at P0, P4, P14, P21 and P56 were 2.3 × 104, 6.2 × 104, 10.4 × 104, 7.1 × 104 and 3.5 × 104, respectively. These results indicate that the number of CST axons at the cervical
intumescence of mouse becomes maximum at P14, and then decreases rapidly to reach
the adult level of 3.5 × 104 (at P56), about 68% of them thus being lost.
Keywords
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Article Info
Publication History
Accepted:
July 13,
1995
Received:
May 19,
1995
Identification
Copyright
© 1996 Elsevier Science B.V. All rights reserved. Published by Elsevier Inc.