[The role of Fos protein in modulation of dental pain in central nerve system].
The aims of this study were to reveal the relationship between Fos protein expression, the transcription of preproenkephalin (PENK) mRNA, and the change of enkephalin (ENK) level initiated by experimental dental pain, and to understand the central modulation mechanism of dental pain. The techniques of Immunohistochemistry in situ hybridization and radioimmunoassay were applied respectively to detect the expression of Fos, the transcription of PENK mRNA, and the change of ENK level in the experimental nucleus of the spinal tract of the trigeminal nerve, caudal part (sp5c) of rats. It was found that Fos protein expression was in a time-dependent manner. Fos appeared half hour after the pain stimulation, and its peak occurred two hours after the pain stimulation, but disappeared slowly four hours later. The transcription of PENK mRNA was seen two hours after the pain stimulation, its peak appeared four hours later and it disappeared eight hours later. The level of ENK increased significantly (P < 0.01) in the caudal part of the spinal tract of the trigeminal nerve four hours after pain stimulation. Fos protein may take a part in the central modulation of dental pain by initiating PENK mRNA transcription which led to the increment of ENK.