LESION-INDUCED CHANGES IN THE CENTRAL TERMINAL DISTRIBUTION OF GALANIN-IMMUNOREACTIVE AXONS IN THE DORSAL COLUMN NUCLEI

Rats that sustained forelimb removal on either embryonic day (E) 16, o n the day of birth (P-0), or transection of the brachial plexus in adu lthood had brainstem sections stained for galanin, calcitonin gene-rel ated peptide (CGRP), or substance P (SP) at various intervals after th ese lesions were made. In normal adult rats, only a few galanin-immuno reactive fibers are present in the cuneate nucleus and most are locate d in its caudal portion. CGRP-positive axons are also sparse in the cu neate and are distributed mainly in the periphery of the nucleus. SP-p ositive axons are seen throughout the cuneate nucleus. In rats that su stained forelimb removals at birth or transection of the brachial plex us in adulthood, dense galanin immunoreactivity was present throughout the cuneate nucleus at all rostrocaudal levels on the side of the bra instem ipsilateral to the lesion. The changes after lesions that were made in the adult animals were apparent within 1 week, the earliest ti me analyzed. Increases in galanin immunoreactivity in the cuneate of a nimals that sustained forelimb removals on P-0 were first visible on P -2. Neither forelimb removal at birth nor brachial plexus lesions in a dulthood had any qualitative effect upon the distribution or density o f CGRP- or SP-immunoreactivity in the cuneate nucleus. Removal of a fo relimb on E-16 did not increase the density of galanin-immunoreactive fibers in the cuneate nucleus. Such lesions also failed to produce any appreciable change in the density of either CGRP- or SP-positive fibe rs in the cuneate nucleus. The present data raise the possibility that large caliber, non-peptidergic primary afferent axons which innervate the cuneate nucleus may express galanin after damage at birth or in a dulthood.