The Changes Of Synaptic Related Protein Expression In Hypothalamus Of Chronic Unpredictable Stress Rats And The Antidepressant Effect Of Penta-acetyl Geniposide

With the accelerated pace of life,more and more people suffer from depression under different types of pressure.The hypothesis of depression mechanisms mainly includes monoamine transmitter hypothesis,receptor hypothesis,neuroendocrine hypothesis and neural plasticity hypothesis.The neural plasticity hypothesis can explain some controversies in other hypotheses.With the development of imaging technology in recent years,accumulating evidence indicated that depression is closely related to the changes of neural plasticity.Therefore,prevention of neural plasticity changes has become one of the main directions of antidepressant therapy.The current antidepressant drugs,especially the third and fourth generation antidepressants,have a higher remission rate and better tolerability,but the cure rate is still about 30%.More researchers pay their attention to traditional Chinese medicine.A large number of studies have shown that some traditional Chinese medicine achieved a better antidepressant effect through regulating HPA axis and exerted synergistic effects with some western medicine.Therefore,herbal therapies can provide prospective alternative/complementary strategies for depression.The main contents of this paper include the following two parts:Part one: The Changes of Synaptic Related Protein Expression in Hypothalamus of Chronic Unpredictable Stress Rats and its Pathological SignificanceObjective: Observe the changes of glutamate AMPA receptor and synaptic related protein expression in hypothalamus of chronic unpredictable stress rats and its pathological significance.Methods: We established a depressed rat model using 3 consecutive weeks of chronic unpredictable mild stress(CUMS).The changes of animal behavior were measured by sucrose preference test and open field test.Serum corticosterone(CORT)levels were detected by Elisa.Immunohistochemistry was used to detect the protein expression of CRH and Glutamate AMPA receptor subunit Glu R1 in paraventricular nucleus(PVN).The co-expression of CRH and Glu R1 in PVN CRH neurons were observed by immunofluorescence double labeling.The m RNA and protein levels of Glu R1 and synapse associated proteins(PSD95,SYP and MAP2)in hypothalamus measured by real time QPCR and western blot analyses,respectively.Results: Compared with the normal group,CUMS rats showed abnormal behaviors(lower sucrose preference,decreased numbers of total crossing squares and rearing)and elevated serum CORT,suggesting that the CUMS depression model was successfully prepared.Immunohistochemistry results showed that the protein expression of CRH and Glu R1 in PVN significantly increased in CUMS rats.Results of immunofluorescence double labeling revealed that CRH and Glu R1 were co-expressed in PVN neurons,indicating Glu R1 located on the cell membrane of CRH neurons.The m RNA and protein expressions of Glu R1 and synaptophysin(PSD95,SYP,MAP2)were significantly increased in hypothalamus of CUMS rats.Interestingly,correlation analysis indicated that the protein levels of Glu R1,PSD95,SYP and MAP2 negatively correlated with depression-like behaviors of rats in the sucrose preference and open field test.Conclusion: The dysregulation of the glutamatergic and synaptic systems in the hypothalamus of CUMS rats may contribute to the CRH neurons hyper-activation in PVN and is closely involved in the depression-like behaviors of rats.Part two: The Effect of Penta-acetyl Geniposideon on Depression-like Behaviors of Chronic Unpredictable Stress Rats and Its MechanismsObjective: To reveal the effect of penta-acetyl geniposideon on depression-like behaviors of chronic unpredictable stress rats and its mechanisms.Methods: Sixty rats were randomly divided into six groups: normal group,CUMS group,penta-acetyl geniposide(25,50,100 mg/kg)-treated groups and fluoxetine(10 mg/kg)-treated group.Except the rats in normal group,CUMS was applied to induce depression in rats.Penta-acetyl geniposide and fluoxetine were intragastric administrated from day 8 to 21 after CUMS exposure.Sucrose preference test,open field test and forced swimming test were used to detection the behaviors of rat.The corticosterone(CORT)serum level,the adrenal index and the hypothalamic corticotrophin-releasing hormone(CRH)m RNA level were assayed.The protein levels of Glu R1 and synapse associated proteins(PSD95,SYP and MAP2)in hypothalamus were measured by western blot analyses.Results: Compared with the normal group,CUMS rats showed abnormal behaviors and HPA axis activation.Penta-acetyl geniposide could reverse the CUMS-induced behavioral abnormalities,as indicated by increased sucrose consumption,improved crossing and rearing behavior,reduced immobility time and increased swimming time.Penta-acetyl geniposide could restore the CUMS-induced overactivity of HPA axis,evidenced by decreased CORT serum level,adrenal gland index and hypothalamic CRH m RNA level.Interestingly,penta-acetyl geniposide could reduce the expressions of Glu R1 and synapse associated proteins in hypothalamus of CUMS rats.Conclusion: Penta-acetyl geniposide can improve the behavior of CUMS rats,and its antidepressant effect may be related to the regulation of HPA axis function and the reduction of the expression of Glu R1 and synapse related proteins.