Screening of differentially expressed genes in the hypothalamus of a rat neuropathic pain model following sciatic nerve injury

Background Neuropathic pain is induced by injury or disease of the nervous system. Most studies have so far focusedonly on a few known molecules and signaling pathways among neurons. However, all signal transmissions involved inneuropathic pain appear to be an integral system at different molecular levels. This study was designed to screen thedifferentially expressed genes of the hypothalamus in chronic constriction injury (CCI) rats and analyze their functions indeveloping neuropathic pain.Methods Ten adult female Sprague-Dawley rats ((200±10) g) were used in experimental group and sham group (n=5 ineach group). Mechanical allodynia tests were performed to ensure that the CCI rat model was constructed successfully.Total hypothalamus RNAs were isolated from each group. Forward suppression subtractive hybridization (SSH) library ofrat hypothalamus was constructed and up-regulated cDNA clones at neuropathic pain states were obtained viasuppressed subtractive hybridization technique and the functions of these genes were analyzed bioinformatically.Results Mechanical allodynia tests showed that the experimental rats had a significantly reduced mechanical allodyniathreshold 3 to 13 days after CCI vs sham surgery rats (P <0.01), indicating that the model was successful. Forward SSHlibrary of the rat hypothalamus was constructed successfully and 26 over-expressed expression sequence tags (ESTs)were obtained from these up-regulated cDNA clones.Conclusion Twenty-six up-regulated genes, involved in the regulation of cell cycle and apoptosis, signal transduction,and neuroprotection, may play key roles in decreasing mechanical withdraw thresholds in CCI rats, which implicates amultidimensional and integrated molecular mechanism at gene level in developing neuropathic pain with the supraspinalcontributions.