Resumen
The corticospinal tract is widely used to study regeneration and is essential for voluntary movements in humans. In young rats, corticospinal axons on the uninjured side sprout and grow into the denervated side. Neurotrophin-3 (NT-3) induces such crossed collateral sprouting in adults. We investigated whether local intraspinal NT-3 infusions would promote collateral sprouting of spared corticospinal terminals from within a partially denervated side, as this would be more appropriate for enhancing function of unilateral and specific movements. Adult rats received a partial bilateral transection of the pyramids, leaving approximately 40% of each tract intact. Vehicle or vehicle plus NT-3 (3 or 10 μg/day) was infused for 14 days into the left side of the cervical (C5/6) or lumbar (L2) cord. The corticospinal processes on the left side were anterogradely traced with cholera toxin B (CTB; which labeled gray matter processes more robustly than biotinylated dextran amine) injected into the front or hind limb area of the right sensorimotor cortex, respectively, 3 days before analysis. Unexpectedly, approximately 40% fewer CTB-labeled corticospinal processes were detectable in the cervical or lumbar gray matter of NT-3-treated rats than in vehicle-infused ones. Vehicle-infused injured rats had more corticospinal processes in the center of the cord than normal rats, evidence for lesion-induced collateral sprouting. NT-3 caused sprouting of local calcitonin gene-related peptide-positive fibers. These results suggest that NT-3 reduces collateral sprouting of spared corticospinal axons from within the denervated regions, possibly because of the injury environment or by increasing sprouting of local afferents. They identify an unexpected context-dependent outgrowth inhibitory effect of NT-3.
Idioma original | English |
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Páginas (desde-hasta) | 875-887 |
Número de páginas | 13 |
Publicación | Neuroscience |
Volumen | 130 |
N.º | 4 |
DOI | |
Estado | Published - 2005 |
Publicado de forma externa | Sí |
Nota bibliográfica
Funding Information:Hayun Zhang, Julie Bunker, Clarrie Lam and Kimberley Jenkins Milton are very much appreciated for their excellent technical support. We wish to thank Regeneron Pharmaceuticals Inc. for their continuing and generous supply of NT-3. Supported by a grant from the International Spinal Research Trust (T.H.), and by the Department of Neurological Surgery at the University of Louisville, Bucks for Brains, Kentucky Spinal Cord and Head Injury Research Trust and Norton Health care.
ASJC Scopus Subject Areas
- General Neuroscience