| Objectives:Depression,a kind of mental disorder with persistent depression as the main symptom,has been widely recognized by the international society and the world for its high prevalence rate,high recurrence rate,high morbidity and high mortality characteristics.But the pathogenesis of depression has not yet fully defined,the use of drugs and treatments for depression are relatively scarce,thus the research on the mechanism and the development of antidepressant drugs can not be separated from the effective animal model of depression.Accurate and reliable animal model is of great significance in the study of depression.The preliminary clinical study of the team initially confirmed that depressed patients’brain are characterized by multi-neurotransmitters disorders,the three antagonizing pairs of neurotransmitters 5-hydroxytryptamine(5-HT)and dopamine(DA),acetylcholine(Ach)and norepinephrine(NE),inhibitory neurotransmitter(INH)and excitatory neurotransmitter(EXC)showed strong antagonistic relationship.The main posture of neurotransmitters in the whole brain area of patients with depression was 5-TH↑ DA↓ NE↑ Ach↓ EXC↓ NH↑ or 5-TH↑ DA ↓NE↑ Ach ↓ EXC↑ INH↓.In this study,the rat model of depression was replicated according to the imbalance and the antagonistic relationship between neurotransmitters of clinical depression.Microinjection of the dopamine D1 receptor antagonist SCH23390 into the hippocampus was used to reduce the DA content in the brain and then affect the balance of neurotransmitters in the brain to establish a new type of animal model of depression,which is effective,stable and lasting,easy to operate and can be quantified,so as to promote the study of depression.The study was divided into two parts to research,in the first part,we made a rat model of depression,explored the appropriate molding drug dose and observed the persistence of depressive symptoms.In the second part,we evaluated the predictive validity of the rat model of depression.Methods:1.Experimental study on the method of making rat model of depression.According to the consumption of sucrose,healthy adult male SD rats were randomly divided into five groups:normal control group,blank control group,low dose molding group,medium dose molding group and high dose molding group.All groups,except the normal control group,were implanted cannula in the left hippocampus.After 1 week of rest,the rats in the low,medium and high dose molding groups were injected,by a microinjector,with different doses(1,2,4μg/μl)of the dopamine D1 receptor antagonist SCH23390 in the hippocampus to establish a depression model.Rats in the blank control group were given the equal volume of 0.9%sodium chloride injection with the same site.The experiments of sucrose consumption,open-field and novelty suppressed feeding tests were used to evaluate the rats behavior,and the change rate of body weight was monitored at four different time points,which is before modeling,1 day after modeling,1 week after modeling,and 2 weeks after modeling.2 weeks after modeling,the contents of IL-1β and TNF-a in cerebrospinal fluid(CSF)were measured by ELISA.The levels of the antagonizing pairs of neurotransmitters in the cerebral cortex and hippocampus were analyzed by the method of high performance liquid chromatography-mass spectrometry(HPLC-MS/MS).We evaluated the depression behavior of rats by the weight change rate and the index of behavioral tests,and screened out the more appropriate molding drug dose.2.Predictive validity evaluation of the new depression rat model According to the consumption of sucrose,healthy adult male SD rats were randomly divided into four groups:blank control group,model group,venlafaxine group and Xiaoyao pill group.After implantation of the cannula for 1 week,rats in the model,venlafaxine and Xiaoyao pill groups were given,by microinjection,with the more appropriate molding drug dose to make depression model.Rats in the blank control group were injected with equal volume of 0.9%sodium chloride injection in the same site.After the model was finished,venlafaxine group rats were treated with venlafaxine hydrochloride(12.5mg/kg/d)and Xiaoyao Pill group rats were treated with Xiaoyao Pill(1.5g/kg/d)by intragastric for 2 weeks.The blank control group and model group rats were given the same amount of distilled water by intragastric for 2 weeks.We used the experiments of sucrose consumption,open-field test,novelty suppressed feeding test and step-down test to evaluate the rats behavior,and monitored the change rate of body weight at three different time points,such as before modeling,1 day after modeling,and 2 weeks after modeling.2 weeks after modeling,HPLC-MS/MS technology was used to detect the contents of neurotransmitters in brain tissue.Results:1.Experimental study on the method of making rat model of depression.Compared with the normal control group,there was no significant difference in the body weight and the indexes of behavioral tests in each group before the model was established(P>0.05).① Compared with the blank control group,1 day and 1 week after modeling,the body weight growth rates of the medium and high dose molding group were significantly decreased(P<0.01).2 weeks after modeling,the body weight growth rates of the low,medium and high dose molding group were significantly decreased(P<0.05 or P<0.01).② Compared with the blank control group,1 day and 1 week after modeling,the sucrose preference rates of the low,medium and high dose molding group were significantly decreased(P<0.05).2 weeks after modeling,the sucrose preference rates of the low and medium dose molding group were significantly decreased(P<0.05).③ Compared with the blank control group,1 day after modeling,the horizontal motion scores of the low,medium and high dose molding group were significantly decreased(P<0.05).1 week and 2 weeks after modeling,the horizontal motion scores of the low,medium and high dose molding group were significantly decreased(P<0.01),and same as the vertical motion scores(P<0.01).④ Compared with the blank control group,1 day after modeling,the feeding latent periods of the low,medium and high dose molding group were significantly increased(P<0.05).1 week after modeling,the feeding inhibition times of the low,medium and high dose molding group were significantly increased(P<0.01 or P<0.05).2 weeks after modeling,the feeding inhibition times of the low,medium and high dose molding group were significantly increased(P<0.05).No significant difference in the levels of IL-1β and TNF-α in the cerebrospinal fluid of each group was observed.Compared with the blank control group,the content of 5-HT,NE and Glu in the hippocampus of the medium dose molding group were significantly increased(P<0.01),and the content of DA and Ach showed decreasing trends(P>0.05).The content of Glu in cerebral cortex was significantly increased(P<0.05),and the content of 5-HT and NE showed increasing trends(P>0.05),the content of DA and Ach showed decreasing trends(P>0.05).2.Predictive validity evaluation of the new depression rat model Compared with the normal control group,there was no significant difference in the body weight and the indexes of behavioral tests in each group before the model was established(P>0.05).After modeling,compared with the blank control group,the weight growth rates of model group,venlafaxine group and Xiaoyao Pill group were significantly decreased(P<0.01),sucrose preference rates were significantly decreased(P<0.05),horizontal motion and vertical motion scores of open field test were significantly decreased(P<0.05),feeding inhibition times were significantly increased(P<0.05).After 2 weeks of intragastric administration,compared with the model group,the body weight growth rates of venlafaxine group and Xiaoyao pill group were significantly increased(P<0.01),the sucrose preference rate of venlafaxine group was significantly increased(P<0.05),the vertical motion scores of venlafaxine group and Xiaoyao pill group increased significantly(P<0.01 or P<0.05),the feeding inhibition time of venlafaxine group decreased significantly(P<0.05),the learning ability and memory ability of venlafaxine group were significantly increased(P<0.01),the learning ability and memory ability of Xiaoyao Pill group were significantly improved(P<0.05 or P<0.01).Compared with the blank control group,the content of 5-HT,NE and Glu in left hippocampus of model group were significantly increased(P<0.01 or P<0.05),and the content of DA and Ach showed decreasing trends(P>0.05).The content of 5-HT,NE and Glu in right hippocampus of model group were significantly increased(P<0.05),and the content of DA and Ach showed decreasing trends(P>0.05).The content of Glu in cerebral cortex was significantly increased(P<0.05),and the content of 5-HT and NE showed increasing trends(P>0.05),the content of DA and Ach showed decreasing trends(P>0.05).After 2 weeks of intragastric administration,compared with the model group,the content of 5-HT,NE and Glu in the hippocampus of venlafaxine group and Xiaoyao Pill group showed decreasing trends(P>0.05),the content of DA and Ach showed increasing trends(P>0.05),and the proportion of neurotransmitters in the cerebral cortex has also been adjusted to varying degrees.Conclusion:1.In this study,a rat model of depression was successfully replicated,the model rats showed decreased interest,lack of pleasure,decreased spontaneous activity,decreased exploratory ability,decreased appetite,and slow weight gain and other typical depressive behavior,which well simulated the depressive symptoms of patients with clinical depression.The model has good stability,and depression symptoms can last for at least 2 weeks.Using the dosage of 2μg/μl is more suitable.The change trend of neurotransmitters in the cerebral cortex of the model rats was similar to the main trend of the neurotransmitters in the whole brain region of the depressed patients.2.Venlafaxine and Xiaoyao Pills can regulate the neurotransmitters in the brain of rats with depression,and reverse the changes in the neurotransmitter level caused by the model,balance the proportion of the antagonizing pairs of neurotransmitters,so as to reverse this model induced depression behavior,indicating that the model has good predictive validity. |
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