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.

The present investigation demonstrates that in squamate reptiles, as already reported for Podarcis sicula (Andreuccetti et al., 2001), the differentiation of pyriform cells from small, stem follicle cells is characterized by the progressive appearance on the cell surface of glycoproteins bearing alpha-GalNAc terminated O-linked side chains. Using a lectin panel (WGA, GSI-A4, GSI-B4, PSA UEA-I, PNA, Con-A, DBA, LCA, BPA, SBA), we demonstrated that, during previtellogenesis, the pattern of distribution of DBA binding sites over the follicular epithelium dramatically changes. In fact, binding sites first appear in follicular epithelium at the time that small cells begin to differentiate; in such follicles, labeling is evident on the cell surfaces of small and intermediate cells. Later on, as the differentiation progresses, the binding sites also become evident on the cell surface of pyriform cells. Once differentiated, the pattern of the distribution of DBA binding sites over the follicular epithelium does not change. By contrast, during the phase of intermediate and pyriform cell regression, DBA binding sites gradually decrease, so that the monolayered follicular epithelium of vitellogenic follicles, constituted only by small cells, shows no binding sites for DBA. It is noteworthy that binding sites for DBA are present on small cells located in contact with the oocyte membrane, but not on those located under the basal lamina or among pyriform cells, and therefore not engaged in the differentiation into pyriform cells. This finding demonstrates that, in squamates, the pattern of distribution of alpha-N-GalNAc containing glycoproteins significantly changes during previtellogenesis, and that these modifications are probably related to the differentiation of small stem cells into highly specialized pyriforms.