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Abstract
Following peripheral axotomy, fluoride resistant acid phosphatase (FRAP) and most
neuropeptides are depleted in the central terminals of axotomised nerves and reduced
in their corresponding cell bodies (DRG) but vasoactive intestinal polypeptide (VIP)
increases. The increase in VIP probably results from a change in gene expression in
other ganglion cells which do not normally express VIP. A quantitative study was performed
to investigate the proportion of DRG cells immunoreactive for different peptides at
increasing times after sciatic nerve section. Retrograde fluorescent neuronal labelling
of sciatic nerve cell bodies by injection of fast blue into the proximal stump was
combined with unlabelled antibody immunohistochemistry for CGRP and VIP. The proportion
of cells immunoreactive for these peptides was quantified between two and fourteen
days post-axotomy. The number of VIP immunoreactive profiles increased significantly
in the first 4 days post-axotomy, followed by a slight decrease before rising again.
In contrast, the number of and CGRP-immunoreactive cell profiles declined to zero
by 14 days post-axotomy. 4 days post-axotomy 50% of VIP positive cells were also immunoreactive
for CGRP. There was neither colocalisation between VIP and FRAP nor between CGRP and
FRAP. It is concluded that many peptidergic DRG cell bodies switch their expression
of peptide to VIP after injury, whereas non-peptide-containing subpopulations do not.