焦虑模型大鼠下丘脑-垂体-肾上腺轴高反应性与糖皮质激素受体蛋白表达降低相关

Hyperactivity of hypothalamus-pituitary-adrenalaxis is associated with reduced expression of glucocorticoid steroid receptor in a rat model of anxiety

目的研究焦虑模型大鼠在应激条件时下丘脑-垂体-肾上腺(hypothalamus-pituitaryadrenal,HPA)轴呈高反应性是与轴本身功能亢进还是与反馈调节中糖皮质激素受体(glucocorticoid steroid receptor,GR)蛋白表达改变相关。方法 SD健康雄性大鼠随机分为对照组(n=20)和焦虑模型组(n=26)。对照组正常饲养。采用不可预知的情绪应激方法建立大鼠焦虑模型。所有大鼠每周称量体质量。造模结束后,通过行为学鉴定造模是否成功。旷场和高架作为应激源刺激大鼠,测定两组大鼠血清中促肾上腺激素和皮质酮水平。Western blot检测GR蛋白在大鼠海马、下丘脑、垂体和肾上腺组织中的表达。结果焦虑模型大鼠体质量增长率与对照组相比明显降低(P<0.01)。高架十字迷宫实验和旷场实验显示:与对照组相比,模型组大鼠进入开臂次数、开臂停留时间、进入开臂次数百分比和进入开臂时间百分比均显著降低(P<0.01);总路程、中央活动路程百分比和中央活动时间百分比均显著降低(P<0.05,P<0.01)。在基础条件下,两组大鼠分泌促肾上腺激素和皮质酮差异无统计学意义(P>0.05);而应激条件下,模型组大鼠分泌两种激素显著高于对照组(P<0.01)。与对照组比较,模型组在大鼠海马、下丘脑和肾上腺组织中GR蛋白表达显著降低(P<0.05,P<0.01),而在垂体中表达差异无统计学意义(P>0.05)。结论焦虑模型大鼠在应激条件下,HPA轴反应性增加与GR所介导的负反馈调节作用减弱有关。

Objective To determine whether the hyperactivity of the hypothalamus-pituitary-adrenal（ HPA） axis in response to stress is associated with the hyperfunction of the HPA axis or with the feedback regulation of glucocorticoid steroid receptor（ GR） expression in rat model of anxiety. Methods Healthy male SD rats were randomly divided into control group（ n = 20） without any stimulation and anxiety model group（ n = 26） exposed to unpredictable emotional stress. All the rats were weighed once a week and at the end of the stimulus,and the behavioral changes of the rats were observed in elevated plus-maze（ EPM） and openfield tests. Serum levels of adrenocorticotropic hormone（ ACTH） and corticosterone were measured in the rats following stimulation with open-field and EPM as the stressors,and the expression of GR in the hippocampal,hypothalamic,pituitary and adrenal tissues was detected with Western blotting. Results The rat models of anxiety showed a significantly lower rate of body weight increase than the control rats（ P〈0. 01）. The rats with anxiety exhibited a significantly lower number and a lower percentage of open arm entry,shorter and lower percentage of retention time in the open arm（ P〈0. 01）,shorter total distance and central time,and lower central distance percentage in the open-field test（ P〈0. 05,P〈0. 01）. No significant differences were found in the serum levels of ACTH or corticosterone between the 2 groups at baseline,but after stress stimulation,their levels became obviously higher in the model group than in the control group（ P〈0. 01）.The protein level of GR was significantly reduced in the hypothalamic（ P〈0. 05） and adrenal tissues（ P〈0. 01） in the model group as compared with the control group,but no significant difference was found in GR level in the pituitary tissue between the 2 groups（ P〉0. 05）. Conclusion The hyperactivity of the HPA axis under stress is associated with the attenuation of GR-mediated negative feedback regulation in rat models of anxiety.