GAP‐43, aFGF, CCK and α‐ and β‐CGRP in Rat Spinal Motoneurons Subjected to Axotomy and/or Dorsal Root Severance

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Abstract
The mRNA levels for growth‐associated protein 43 (GAP‐43), acidic fibroblast growth factor (aFGF), α and β‐calcitonin gene‐related peptide (CGRP), cholecystokinin (CCK) and choline acetyltransferase (ChAT) in rat lumbar spinal motoneurons were studied by in situ hybridization 1, 5 and 21 days and 20 weeks following unilateral peripheral nerve sectioning, ventral rhizotomy or dorsal rhizotomy. Furthermore, CGRP‐ and aFGF‐like immunoreactivities in the ventral horn were studied using immunohistochemistry. One to 21 days after axotomy, GAP‐43 and α‐CGRP mRNAs increased in lesioned motoneurons, while the aFGF mRNA levels were marginally higher in motoneurons on the lesion side as compared to the control side. β‐CGRP, CCK and ChAT mRNA levels, on the other hand, decreased during the short‐term response (1 – 21 days) to axotomy. After ventral rhizotomy, but not peripheral axotomy, there was complete disappearance of aFGF‐like immunoreactivity in the ventral root proximal to the lesion. In animals subjected to long‐term survival (20 weeks) after peripheral axotomy, the expression of all studied substances had returned to normal levels. Unilateral dorsal rhizotomy did not induce any substantial short‐ or long‐term shifts in the cellular expression of the GAP‐43, aFGF, CGRP and CCK peptides or their mRNAs in motoneurons of lesioned segments. These results indicate that peptides/proteins in motoneurons are expressed differentially after axotomy. Whereas α‐CGRP and GAP‐43 are up‐regulated, CCK and β‐CGRP become down‐regulated and aFGF is largely unaffected.