The Role Of Serotonin In The "Gut-brain Stem Axis" In Restraint Water-Immersion Stress

Restraint water-immersion stress(RWIS)is considered to be a mixture of physical and psychological stressor.This stress can cause emotional changes such as fear,anger,anxiety,and despair in rats,and disturbances of gastrointestinal functions such as increased gastric movement,increased gastric acid secretion,and decreased gastric mucosal blood flow,which leads to gastric mucosal damage in rats.This stress model is often used to study the mechanism of stress gastric ?Lcers.The gut-brain axis is a two-way reg?Latory axis for the interaction of the gastrointestinal tract with the central nervous system.The various levels of the brain receive various incoming information from the gastrointestinal tract,and after integration,reg?Late the gastrointestinal mucosa,blood vessels,glands,smooth muscle and intestinal microorganisms through the autonomic nervous system.Our previous research found that the expression of c-Fos protein in the paraventric?Lar nucleus of the hypothalamus,the solitary nucleus of the brain stem(NTS),the dorsal vagus nerve(DMV)and the gastrointestinal myenteric plexus of the hypothalamus increased significantly.These res?Lts indicates that the gut-brain stem axis participates in the process of Restraint water-immersion stress,but it is not clear which type of neurons in the gut-brain stem axis participate in the stress process.5-HT,a neurotransmitter widely present in the brain and digestive tract,and plays an important role in reg?Lating intestinal-brain information communication and gastrointestinal function.When the gastrointestinal tract is stressed or chemically stim?Lated,intestinal chromaffin cells release a large amount of 5-HT which binds to corresponding receptors,and transmits the gastrointestinal sensory information to the brain through the vagus nerve,on the other hand,5-HT in the nucleus raphe magnus binds to receptors on NTS and DMV to reg?Late gastrointestinal function.So,1.Does the 5-HT signaling system of the i gut-brain stem axis participate in the RWIS process,and what changes have 5-HT synthase,receptors,and transporters in the gastrointestinal tract and brain stem at various times of RWIS?2.What effect does the injection of 5-HT3 R inhibitor Palonosetron on the nucleus tractus solitarius affect the activity of various neurons in the intestinal myenteric plexus and the function of the gastrointestinal tract?The following experiments are designed for the above problems:Experimental Study 1: According to the different stress time,the experimental rats were divided into three groups,the control group,RWIS 1h group,and RWIS 3h group,respectively,using immunohistochemistry,Western Blot and qRT-PCR technology to detect rat colon muscle The expression of 5-HT,5-HT3 R,5-HT4 R,SERT,and TPH in the interspinous plexus,midbrain large nucleus(DR),midbrain aqueduct ventral(vlPAG),and brainstem NTS and DMV to explore whether 5-HT in the gut-brain stem axis is involved in the RWIS process..Experimental study 2: The rats were divided into control group,RWIS1 h group,RWIS1 h + saline group,RWIS1 h + palonosetron group(inhibitor of 5-HT3 R receptor).Immunohistochemistry and Western Blot technique were used to detect the expression of p-ERK1 / 2,GFAP,ChAT and NOS in rat colonic myenteric plexus,and to explore the effect of 5-HT on intestinal neuronal activity and neurotransmitters.Experimental study three: grouped with experime nt two,using Western Blot and ELISA technology to detect the expression of Occludin,skeleton protein Claudin-1,gastric mucin MUC5 AC in the colon of experimental rats,and observe the damage status of gastric ulcer Discuss what effect 5-HT has on gastrointestinal function.The study found:1.The expression of 5-HT3 R in colonic myenteric plexus and brainstem NTS and DMV in RWIS3 h group was significantly increased compared with the control group(P <0.01);after RWIS3 h,5-HT and TPH in DR and vlPAG The expression of TPH and the expression of TPH in colonic myenteric plexus were significantly increased compared with the control group(P <0.01);and after 3 hours of RWIS,colonic myenteric plexus and brainstem NTS,5-HT4 R in DMV,SERT,DR and vlPAG Compared with the control group,the expression of SERT was significantly reduced and the difference was significant(P <0.01).These results indicate that the 5-HT signaling system is involved in the RWIS process.2.The results of immunohistochemistry and Western Blot experiments found that the expression of p-ERK1 / 2,GFAP,ChAT and NOS in colonic myenteric plexus of RWIS1 h + palonosetron group were reduced and different compared with RWIS1 h + saline group.Significantly(P <0.01).This indicates that during the process of RWIS,the brainstem 5-HT system is activated,and the activity of neurons and astrocytes in the intestinal myenteric plexus is regulated by combining 5-HT3 R of the nucleus tractus solitarius.3.The results of gastric injury detection and ELISA experiments showed that compared with the RWIS1 h + normal saline group,the gastric mucosal injury was significantly reduced in the RWIS1 h + palonosetron group,and the expression of MUC5 AC in the stomach increased and the difference was significant(P <0.01),Western Blot experiments found that the expression of Claudin-1 and Occludin in the colon was significantly reduced(P <0.01).These results indicate that during the RWIS process,the 5-HT signaling system in the brain stem is activated,and by binding to 5-HT3 R in the nucleus tractus solitarius,the activity of neurons and astrocytes in the intestinal myenteric plexus is affected,resulting in gastric Disturbance of intestinal function.