Effects of red nucleus ablation and exogenous neurotrophin-3 on corticospinal axon terminal distribution in the adult rat.
Collateral sprouting of undamaged descending axons is one potential mechanism for recovery of function after incomplete spinal cord injury. In this study, we have investigated whether terminals of the intact corticospinal tract in the rat would sprout following ablation of a parallel descending pathway, the rubrospinal tract. No sprouting was detected after this injury alone. However, the combination of rubrospinal tract ablation with administration of 100ng neurotrophin-3 to neurons of the corticospinal tract resulted in marked increased density of corticospinal innervation in the superficial dorsal horn. There was no effect of administration of neurotrophin-3 alone and increase in axon density was not detected in the deep dorsal horn. These results imply that spontaneous sprouting of undamaged corticospinal axons does not occur following ablation of a parallel tract system, although collateral sprouting can be induced through a combination of the lesion plus exogenous growth factor. Induced change in corticospinal terminal density is detected in the superficial dorsal horn only, supporting the hypothesis that this is an area particularly supportive of circuit reorganisation.
Jeffery
N D
ND
Department of Anatomy and Developmental Biology, Medawar Building, University College London, Gower Street, WC1E 6BT, London, UK. ndj1000@cam.ac.uk
Fitzgerald
M
M
D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D003714:Denervation; D003911:Dextrans / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D008297:Male; D009416:Nerve Regeneration / Q000187:drug effects* / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects* / Q000502:physiology; D020933:Neurotrophin 3 / Q000378:metabolism / Q000494:pharmacology*; D020671:Posterior Horn Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D011712:Pyramidal Tracts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D017378:Quinolinic Acid / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology; D012012:Red Nucleus / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D013119:Spinal Cord Injuries / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology
D003911:Dextrans; D005456:Fluorescent Dyes; D020933:Neurotrophin 3; C076397:biotinylated dextran amine; D001710:Biotin; D017378:Quinolinic Acid