Fos-like immunoreactivity increases in the lumbar spinal cord following a chronic constriction injury to the sciatic nerve of rat

A chronic constriction injury (CCI), transection injury, or sham injury to the sciatic nerve was induced in 30 rats. Rats were then sacrificed at 1, 3, 5, 10, and 20 days following injury, and the number of cells immunohistochemically labeled for Fos-like immunoreactivity (Fos-LI) was determined in random sections from the lumbar 4 and 5 (LA and 1,5) spinal segments. Non-parametric statistics (Wilcoxon) were used to compare the number of labeled cells ipsilateral to the injury to the number of labeled cells on the contralateral side. At 1 and 5 days following injury, in all treatment groups, significantly more labeled cells (P < 0.05) were observed ipsilaterally. In addition, at 3 and 10 days following injury, the CCI groups exhibited significantly more labeled cells ipsilaterally. The significant increases for the CCI groups ranged from 161% to 360%. Generally, increases were greater for the CCI groups. These results indicate that Fos-LI increases to a greater extent and for a longer duration following the CCI than following either a transection or sham injury.