Nerve reinnervation and itch behaviour in a rat burn wound model

ABSTRACT

In this study, we investigated whether post-burn itch in rats, after a full thickness burn, is correlated to the nervous reinnervation of the burn wound area. For this purpose, we determined scratching duration (expressed as sec/hr) at 24 hours, 2, 4, 8 and 12 weeks post-burn and combined this with immunohistochemistry for protein gene product 9.5 (PGP9.5) to identify all nerve fibers, calcitonin gene related peptide (CGRP) to identify peptidergic fibers, tyrosine hydroxylase (TH) for sympathetic fibers and growth-associated protein 43 (GAP-43) for regrowing fibers.

We found a modest, but highly significant, increase in scratching duration of all burn wound rats from 3 to 12 weeks post-burn (maximally 63±9.5 sec/hr compared to sham 3.1±1.4 sec/hr at 9 weeks). At 24 hours post-burn, all nerve fibers had disappeared from the burn area. Around 4 weeks post-burn PGP 9.5- and CGRP-immunoreactive nerve fibers returned to control levels. TH- and GAP-43-IR nerve fibers, which we found to be almost completely co-localized, did not regrow. No correlation was found between scratching duration and nervous reinnervation of the skin.

The present results suggest that in rat, like in human, burn wound healing will induce increased scratching, which is not correlated to nervous reinnervation. This article is protected by copyright. All rights reserved.