| dc.description.abstract | Neuropeptides show dynamic changes in expression after nerve injury, and have been
implicated in chronic pain states. I sought to compare expression of two peptides which
are upregulated after nerve injury, galanin and Reg2, and to determine the subtypes of
dorsal root ganglion (DRG) cells in which they are expressed.
Rats underwent unilateral, L5 spinal nerve ligation (SNL) with recovery for 1 or
7 days. Galanin and Reg2 were expressed in 20% and 8% of DRG cells at 1 day, and
49% and 5% at 7 days, respectively. At 1 day, galanin was mainly expressed in CGRPpositive
DRG cells (62% of galanin cells); this expression was maintained at 7 days. At
1 day, galanin was expressed in few IB4-positive DRG cells (14% of galanin cells), but
expression in IB4 cells significantly increased by 7 days (30% of galanin cells). Galanin
was also coexpressed with TRPV2 (9%). Reg2 was coexpressed in 48% of galanin cells
(7 days) but not coexpressed with TRPV2 and sparsely with CGRP. Using isolated DRG
cultured in BSF2 supplemented with 2% foetal calf serum (FCS), galanin and Reg2 were
expressed in 36.5% and 23.3% after 72hrs. Addition of IL6 (40 ng/mL in FCSsupplemented
BSF2) increased galanin expression after 24 and 48hrs growth by 6.7%
and 13.1%, respectively. ED1-positive cells were shown infiltrating the spinal nerve and
associated with the ganglion by 7 days post-SNL.
These results show Reg2 is more selectively expressed after L5 SNL than
galanin. Both peptides show a complex temporal profile of expression. Galanin is
upregulated initially in CGRP-cells and then in IB4/P2X3-cells, whereas Reg2 is
expressed initially in IB4/P2X3-cells and then in larger cells. The factors that
differentially regulate galanin, and potentially Reg2, in these cell populations remain
unknown but it is hypothesized that IL6, or a related cytokine, drives-up galanin
expression in IB4/P2X3-cells by 7 days but that the early upregulation in CGRP-cells is
a direct consequence of axotomy. | en_US |
