NGF but not NT-3 or BDNF prevents the A fiber sprouting into lamina II of the spinal cord that occurs following axotomy.
There is a stereotypical pattern of primary afferent terminations within the mature spinal cord; however, this pattern is not immutable. Peripheral axotomy causes A fibers to sprout into lamina II, a region from which they are normally excluded. We have investigated the role of neurotrophins in this response. Rats which had undergone sciatic axotomy were treated intrathecally with NGF, BDNF, or NT-3. A fibers were visualized using transganglionic labeling with cholera toxin B subunit; small fibers were visualized using CGRP immunostaining. NGF (12 microg/day for 2 weeks), but not NT-3 or BDNF, prevented both the axotomy-induced reduction in CGRP staining within lamina II and the sprouting of A fibers into this region. It is likely that the prevention of A fiber sprouting is a secondary consequence of NGF rescuing small fibers. This effect of NGF on dorsal horn sprouting has implications both for our understanding of the maintenance of CNS connectivity and for the treatment of neuropathic pain states.
Bennett
D L
DL
Department of Physiology, United Medical and Dental Schools (St Thomas' Campus), Lambeth Palace Road, London, SE1 7EH, United Kingdom.
French
J
J
Priestley
J V
JV
McMahon
S B
SB
D000818:Animals; D001369:Axons / Q000502:physiology*; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002772:Cholera Toxin; D003714:Denervation; D007158:Immunologic Techniques; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009416:Nerve Regeneration / Q000187:drug effects*; D020933:Neurotrophin 3; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000502:physiology / Q000648:ultrastructure; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology*; D013194:Staining and Labeling
D019208:Brain-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D020933:Neurotrophin 3; D002772:Cholera Toxin; D015740:Calcitonin Gene-Related Peptide