摘要：

AIM: To determine whether Salmonella Typhimurium (STM)in gastrointestinal tract can induce the functional activationof brain, whether the vagus nerve involves in signalingimmune information from gastrointestinal tract to brain andhow it influences the immune function under naturalinfection condition.VETHODS: Animal model of gastrointestinal tract infectionin the rat was established by an intubation of SalmonellaTyphimurium (STM) into stomach to mimic the condition ofnatural bacteria infectionSubdiagphragmatic vagotomy wasperformed in some of the animals 28 days before infection.The changes of Fos expression visualized withimmunohistochemistry technique in hypothalamicparaventricular nucleus (PVN) and superaoptic nucleus(SON) were counted. Meanwhile, the percentage and theMean Intensities of Fluorescent (MIFs) of CD4 + and CD8 +T cells in peripheral blood were measured by using flowcytometry (FCM), and the pathological changes in ileumand mesenteric lymph node were observed in HE stainedsections.RESUTLTS: In bacteria-stimulated groups, inflammatorypathological changes were seen in ileum and mesentericlymph node. The percentages of CD4 + T cells in peripheralblood wera decreased from 42 % +4.5 % to34% +4.9 % (P< 0.05) and MIFs of CD8 + T cells were also decreased from2.9 + 0.39 to 2.1 + 0.36 ( P< 0.05) with STM stimulation. Allof them proved that our STM-infection model was reliable.Fos immunoreactive (Fos-ir) cells in PVN and SONincreased significantly with STM stimulation, from 189 + 41 to467+62 (P< 0.05) and from 64+21 to 282± 47 (P< 0.05)individually, which suggested that STM in gastrointestinaltract induced the functional activation of brain.Subdiagphragmatic vagotomy attenuated Fos expression inPVN and SON induced by STM, from 467 ± 62 to 226 ± 45 ( P< 0.05) and from 282 ± 47 to 71 ± 19 ( P < 0.05) individually,and restored the decreased percentages of CD4 ± T cellsinduced by STM from 34 % ± 4.9 % to original level 44 % ± 6.0 % ( P < 0.05). In addition, subdiagphragmstic vagotomyitself also decreased the percentages of CD8 ± T cells (from28 % ±3.0 % to21 % +5.9 %, P<0.05) and MIFs of CD4+(from6.6±0.6to4.9±1.0, P<0.05) andCD8+ Tcells(from2.9±0.39 to1.4± 0.34, P<0.05). Both of themmanifested the important role of vagus nerve in transmittingimmune information from gut to brain and maintaining theimmune balance of the organism.CONCLUSION: Vagus nerve does involve in transmittingabdominal immune information into the brain in STMinfection condition and play an important role inmaintenance of the immune balance of the organism.

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