Abstract:

Objective:The aims of this study were to reveal the relationship between Fos protein expression, the transcription of pre- proenkephalin (PENK) mRNA, and the change of enkephalin (ENK) level initiated by experimental dental pain, and to under- stand the central modulationmechanism of dental pain.Methods:The techniques of Immunohistochemistry in situ hybridization and radioimmunoassay were applied respectively to detect the expression of Fos, the transcription of PENKmRNA, and the change of ENK level in the experimental nucleus of the spinal tract of the trigeminal nerve, caudal part (sp5c) of rats.Results:Itwas found that Fos protein expression was in a time-dependant manner. Fos appeared half hour after the pain stimulation, and its peak oc- curred 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 in- creased significantly (P<0.01) in the caudal part of the spinal tract of the trigeminal nerve four hours after pain stimulation. Conclusion:Fos protein may take a part in the central modulation of dental pain by initiating PENKmRNA transcriptionwhich led to the increment of ENK.

Key words: dental pain modulation, Fos protein, preproenkephalin, enkephalin