Apoptotic genes expression in the lumbar dorsal horn in a model neuropathic pain in rat.

This study combines behavioural, molecular and morphological approaches to assess the occurrence of apoptosis in the rat spinal cord by 14-day sciatic nerve chronic constrictive injury (CCI). Thermal allodynia developed in the corresponding footpad 2-3 days after surgery, while morphological features, evaluated 14 days later, consisted in a decrease (23 +/- 7%) in laminae I-III cell number ipsilateral to CCI. Apoptosis occurrence was possibly suggested by the presence of some TUNEL-positive nuclei in this territory. The mRNA expression levels of the bcl-2 genes family was changed as follows: bax increased up to 40% in CCI vs the sham rats, while bcl-2 did not change; bcl-xS massively decreased (by 70% and 100%), while bcl-xL increased (by 40%) in CCI rats. Western blot analysis showed no change either on poly-ADP ribose polymerase (PARP) or p53 transcription factor in CCI and sham rats. These data suggest that in a chronic pain condition, where the acute phase has already resolved, specific apoptotic genes are still operative and possibly may serve as a critical change for cells surviving in the chronic pain state.