Expression of 5-HT2A receptor mRNA in rat nucleus raphe magnus neurons after peripheral inflammation

Aim: Examine the expression of 5-HT2A receptor mRNA and co-localization of 5-HT2A receptor mRNA with 5-HT immunoreactivity in nucleus raphe magnus (NR M) neurons following carrageenan inflammation. Methods: in situ hybridizati on (ISH) and combining fluorescent ISH with immunofluorescent histochemical double staining technique were used in the present study. Results: 5-HT2A receptor mRNA was expressed in moderate level in NRM neurons. Following car rageenan inflammation, the expression of 5-HT2A receptor mRNA in NRM was gr eatly increased. The peak occurred at 3-8 h and then there was a clear decr ease at 24 h after injection of carrageenan. Only a few 5-HT2A receptor mRN A and 5-HT immunoreactive double labeled cells were observed in NRM, and th e number of the double labeled cells had no obvious change following carrag eenan inflammation. Conclusion: The synthesis of 5-HT2A receptor was increa sed in non-serotonin rather than serotonin neurons of NRM during peripheral inflammation.