Effects Of Chemical Stimulation Of Dorsomedial Thalamic Nucleus On Gastric Function

The restraint water-immersion stress for rat is a powerful complex stimuli, it can producedisorders including gastric motility hyperactivity, increased gastric acid secretion and otherphenomena, but also make the body temperature of rats decline and manic mood. Zhao Dongqin,Li Ying, et al. found three nuclei in the thalamus has Fos-positive neurons significant expressionin RWIS process, including thalamic dorsomedial nucleus (MD), paraventricular nucleus (tPVN),centralmedial nucleus (CM), it indicated that they are involved in the RWIS. Li Ying found thesynaptic plasticity of the three nuclei increased in different degrees during RWIS by usingsynaptophysin (SYN) and synapsin I as the marks of neuronal synaptic plasticity, this resultfurther validated this conclusion.As an integrated part of visceral and somatic activity, is MDinvolved in the regulation of the gastric secretion and motor functions? If it participates in theregulation of gastric function, and than what role it plays?Is it excitatory effect or inhibitoryeffect? These problems have not been reported.In this paper, the experimental protocols were designed to resolve these problemsmentioned above.Experiments were divided into two parts:The first part, we investigated the effect of different doses of L-Glu injected into the MD ongastric motility. The experiment was divided into five groups: the first group, as a control group,the saline (0.1μl) was injected into right side of MD; the second group, the low dose of L-Glu(1nmol=0.1μl×0.01mol/L) was injected into the right side of MD; the third group, the middledoses of L-Glu (10nmol=0.1μl×0.1mol/L) was injected into the right side of MD;the fourthgroup, the high doses of L-Glu (10nmol=0.1μl×0.1mol/L) was injected into the right side ofMD; The fifth group, the ultra-high-dose of L-Glu(200nmol=0.1μl×2mol/L) was injected intothe right side of MD.We recorded the gastric motility curve via RM620system by connectingalatex balloon with a pressure transducer into pylorus, investigating the change of gastricmotility before and after microinjection of drug. The data we collected, including gastric motilitycontraction wave frequency, duration, amplitude, and gastric motility index within15min beforeand after drug injection. As a unit of time in5min, we found that the total magnitude of gastric motility, total duration and every minute gastric motility index were no significant changeswithin15min after injection of saline or four different doses of L-Glu, compared with thatbefore injection. This suggests that the dose range1-200nmol of L-Glu injected into MD doesnot affect gastric motility.The second part, we investigate the effect of different doses of L-Glu injected into the MDon gastric acid secretion. Experiment was divided into four groups: the first group, as a controlgroup, the saline (0.1μl) was injected into right side of MD; the second group, the low dose ofL-Glu (1nmol=0.1μl×0.01mol/L) was injected into the right side of MD; the third group, themiddle doses of L-Glu (10nmol=0.1μl×0.1mol/L) was injected into the right side of MD;thefourth group, the high doses of L-Glu (10nmol=0.1μl×0.1mol/L) was injected into the rightside of MD.The normal saline was infused into stomach through a tube, and the infused salinewas collected from another tube into the pyloric part.After measuring the volume and pH of thecollected saline,we computed the production of H+. As a unit of time in20min, we found thatgastric acid secretion were no significant changes within1h after injection of saline or low、middle doses of L-Glu, but high doses produced significant inhibitory effect. This suggests thatthe low and middle dose of L-Glu injected into MD does not affect gastric motility, but highdoses can inhibit gastric acid secretion.