Study On The Relationship Between High Reactivity Of Hypothalamus Pituitary Adrenal Axis And Corticosteroid Receptor In Anxiety Model Rats

Objective: To study whether the high reactivity of the hypothalamus pituitary adrenal(HPA)axis in the model of stress rats is related to the hyperthyroidism of the axis itself or to the change of the corticosteroid receptor.Methods: SD healthy male rats were randomly divided into two groups: control group(n=20)and model group(n=26).The model of rat anxiety was established by unpredictable emotional stress method.The control group was given normal feeding.The weight of all rats was weighed every week and the modeling was successful by behavioral experiments after modeling.After the end of the stimulus,their behavioral were observed through elevated plus-maze(EPM)and open-field test.The rats were stimulated with EPM and open-field as stressor in order to measure the serum levels of ACTH and corticosterone.The mineralocorticoid steroid receptor(MR)and glucocorticoid steroid receptor(GR)m RNA levels in the hippocampus of the two groups were detected by real-time fluorescence quantitative PCR.The expression of GR in the hypothalamus,pituitary and adrenal tissues in the m RNA expression level.The expression of MR and GR protein in hippocampus and GR in hypothalamus,pituitary and adrenal gland tissues were detected by Western blot.Results:(1)Compared with the control group,the body weight growth rate of anxiety rats was significantly decreased(P<0.01).(2)The rats from the anxious group had significantly lower open arm entry(OE),the OE%,the open arm time(OT)and OT%(P<0.01),and shorter total distance and central time,and lower central distance percentage in the open-field test(P<0.05,P<0.01).(3)There were no significant differences in the secretion of ACTH and corticosterone between the 2 groups under baseline.After stress induction,the levels were obviously higher in the model group than the control group(P<0.01).(4)Compared with the control group,There was no significant difference in MR m RNA expression between the model group and the hippocampus(p>0.05);The expression level of GR m RNA in the model group was significantly lower than that in the hippocampus,hypothalamus,pituitary gland and adrenal gland(p<0.01,p<0.05).(5)Compared with the control group,There was no significant difference in MR protein expression between the model group and the hippocampus(p>0.05);the protein level of GR was reduced in the hypothalamic and adrenal tissues(P<0.05,P<0.01)in the model group,but no difference was seen in the pituitary(P>0.05).Conclusion: Under stress,the HPA axis of the anxiety model rats was associated with GR-mediated negative feedback regulation.