The Interaction Of Neurons And Astrocytes Of "Brain-gut Axis" In Restraint Water-immersion Stress

Restraint water-immersion stress(RWIS)is a composite stress model,which can cause psychological and physiological reactions in rats within a few hours,such as rapid increase of gastric acid secretion,acute gastric mucosa lesion,gastrointestinal function disorders,hypothermia.The central nervous system and gastrointestinal tract can exchange information through the neuro-endocrine network to regulate gastrointestinal function.This relationship,commonly called the“brain-gut axis”.Most stress reactions lead to increased sympathetic activity in the brain-gut axis,but parasympathetic activities are enhanced in RWIS.Our previous experimental studies found that the expressions of c-Fos and GFAP in the dorsal motor nucleus of the vagus(DMV),nucleus tractus solitarius(NTS),and Enteric nervous system(ENS)were significantly increased in RWIS,indicating that neurons and astrocytes of the “brain-gut axis” are jointly involved in RWIS.At the same time,studies have found that hippocampal astrocytes were involved in post-traumatic stress disorder and protect neurons from oxidative stress and nitric stress,but the role of astrocytes of the "brain-gut axis" in RWIS,the interaction and mechanism between astrocytes and neurons have not been reported.Then,we propose the following questions:1.Do the astrocytes affect the neurons in DMV?NTS and ENS of the “brain-gut axis” and gastrointestinal function in RWIS?2.Which pathway does astrocyte affect neurons of DMV?NTS and ENS in RWIS?We designed the following experiments:1.Experimental animals were randomly divided into four groups(RWIS 0h?1h?2h and 3h),and the expression of GFAP in NTS?DMV?jejunum and colon were detected by Western blot technology and immunohistochemical techniques.Then the experimental animals were randomly divided into control group and experimental group.The control group was injected with normal saline and the experimental group was injected with L-?-aminoadipate(L-AA)in the lateral ventricle,a specific inhibitor of astrocytes.After RWIS for 1 hour,the expressions of c-Fos?GFAP?NOS and ChAT in NTS?DMV?jejunum and colon were detected by Western blot technology and immunohistochemical techniques to explore the effect of astrocytes on neuronal activation of the “brain-gut axis” in RWIS.2.Experimental animals were randomly divided into control group and experimental group.The control group was injected with normal saline and the experimental group was injected with carbenoxolone(CBX)in the lateral ventricle.After RWIS for 1 hour,the expressions of c-Fos?GFAP?NOS and ChAT in NTS?DMV ? jejunum and colon were detected by Western blot technology and immunohistochemical techniques to explore the regulation mechanism of astrocytes on neuronal activation of the “brain-gut axis” in RWIS.3.Experimental animals were randomly divided into control group and experimental group.The control group was injected with normal saline and the experimental group was injected with L-AA?CBX in the lateral ventricle.After RWIS for 1 hour,Western blot technology was used to detected the expressions of Occludin protein in gut and ELISA technology were used to detected the expressions of MUC5 AC protein in the stomach to explore the effect of astrocyte on gastrointestinal function in RWIS.Experimental results showed that:1.In different RWIS time,the expression of GFAP in NTS,DMV,jejunal and colon was different.The expression of GFAP in NTS and DMV was highest at RWIS 1h.The expression of GFAP in the jejunal and colon was increased with the increase of RWIS time.Compared with the control group,the expressions of c-Fos?GFAP?ChAT and NOS in DMV?NTS?jejunum and colon of the experimental group were significantly decreased after intracerebroventricular injection L-AA and RWIS for 1 hour.These results suggested that astrocytes of the “brain-gut axis” participated in neuronal activation in RWIS.2.Compared with the control group,the expressions of c-Fos?GFAP?ChAT and NOS in DMV ? NTS ? jejunum and colon were significantly decreased after intracerebroventricular injection CBX and RWIS for 1 hour.It suggests that astrocytes may participate in the RWIS by regulating the activation of neurons through the gap junction.3.Compared with the control group,after intracerebroventricular injection L-AA?CBX and RWIS for 1h,the expression of MUC5 AC protein in the stomach was decreased,while the expression of occludin protein was increased.It suggests that astrocytes in “brain-gut axis” may play a protective role in gastrointestinal function.