AIM:To prove that neurons in the different structures ofthe brainstem that express tyrosine hydroxylase (TH) areinvolved in the transmission and modulation of visceral orsomatic nociceptive information in rat.METHODS:Immunohistochemical double-staining methodwas used to co-localize TH and Fos expression in neuronsof the rat brainstem in visceral or subcutaneous noxiousstimulation models.RESULTS:Neurons co-expressing TH/Fos were observedin lateral reticular nucleus (LRT),rostroventrolateral reticularnucleus (RVL),solitary tract nucleus (SOL),locus coeruleus(LC),A5,A7 neuronal groups and ventrolateral subdivisionof the periaqueductal gray (vlPAG) in both models.But theproportion and number of the double-labeled neuronsresponding to the two noxious stimuli were significantlydifferent in the LRT,RVL and LC nuclei.The proportion andnumber of the TH/Fos double-labeled neurons in the visceralpain model were smaller than that in the subcutaneous painmodel.However,in the case of SOL,they were similar inthe two models.CONCLUSION:Differences of Fos expression in THimmunoreactive neurons in animals after visceral and somaticnoxious stimulation indicate that the mechanisms of thetransmission and modulation of visceral nociceptiveinformation in the brainstem may be different from that ofsomatic nociceptive information. AIM: To prove that neurons in the different structures of the brainstem that express tyrosine hydroxylase (TH) are in viral and transmission of modulation of visceral orsomatic nociceptive information in rat. METHODS: Immunohistochemical double-staining method was used to co-localize TH and Fos expression in neurons of the rat brainstem in visceral or subcutaneous noxiousstimulation models .RESULTS: Neurons co-expressing TH / Fos were observed in lateral reticular nucleus (LRT), rostroventrolateral reticular nucleus (RVL), solitary tract nucleus (SOL), locus coeruleus (LC) A7 neuronal groups and ventrolateral subdivision of the periaqueductal gray (vlPAG) in both models. But theproportion and number of the double-labeled neuronsresponding to the two noxious stimuli were significantly different from the LRT, RVL and LC nuclei.The proportions and number of the TH / Fos double-labeled neurons in the visceralpain model were smaller than that in the subcutaneous pain model. Despite, in the case of SOL, they were s imilar inthe two models. CONCLUSION: Differences of Fos expression in THimmunoreactive neurons in animals after visceral and somatic noxious stimulation indicate that the mechanisms of the transmission and modulation of visceral nociceptive information in the brainstem may be different from that of somatic nociceptive information.