促肾上腺皮质激素释放激素对下丘脑神经元胞浆内环磷酸腺苷和Ca2+浓度的调节作用

背景:在应激反应中,下丘脑-垂体-肾上腺皮质轴的激活对下丘脑促肾上腺皮质激素释放激素表达的增加起着关键的作用。然而关于通过何种途径调控下丘脑神经元表达促肾上腺皮质激素释放激素的神经内分泌活性,促肾上腺皮质激素释放激素能否激活下丘脑神经元,尚不十分清楚。目的:通过外源性促肾上腺皮质激素释放激素刺激培养下丘脑神经元,以观察细胞内环磷酸腺苷和胞浆内钙离子浓度的变化。设计:观察对比实验。单位:解放军第三军医大学大坪医院野战外科研究所,首都医科大学附属天坛医院神经外科。材料:实验于1999-12/2002-03在解放军第三军医大学大坪医院完成。取孕17d胎鼠下丘脑分散培养下丘脑神经元。方法:用外源性促肾上腺皮质激素释放激素刺激培养下丘脑神经元,促肾上腺皮质激素释放激素1受体特异性拮抗剂CP-154526预先处理下丘脑神经元。将培养的细胞分组:①促肾上腺皮质激素释放激素(10-12,10-10,10-8,10-6mol/L)刺激组。②预先用CP-154526(500μmol/L)处理再用促肾上腺皮质激素释放激素(10-12,10-10,10-8,10-6mol/L)刺激组。③分别设置相应的正常对照组,正常对照组用等渗盐水刺激。用PTI荧光成像系统测量和分析外源性促肾上腺皮质激素释放激素对培养下丘脑神经元胞浆内游离钙浓度变化,用放射免疫方法测定神经元内环磷酸腺苷含量。主要观察指标:①下丘脑神经元胞浆内游离钙浓度。②下丘脑神经元内环磷酸腺苷含量。结果:正常对照组的下丘脑神经元胞浆内游离钙浓度和环磷酸腺苷含量较低,外源性促肾上腺皮质激素释放激素刺激后,胞浆内游离钙浓度立即升高,神经元胞浆内环磷酸腺苷生成明显增加[(240±22),(153±11)nmol/L;(3.26±0.19),(0.44±0.02)pmol/dish,P<0.01];CP-154526可明显抑制促肾上腺皮质激素释放激素(10-6mol/L)刺激的下丘脑神经元胞浆内游离钙浓度和环磷酸腺苷含量的生成[钙离子浓度:(240±22),(171±16)nmol/L;环磷酸腺苷含量:(3.26±0.19),(2.33±0.21)pmol/dish,P<0.01]。结论:促肾上腺皮质激素释放激素可通过与其1受体结合直接作用于下丘脑神经元,使神经元胞浆内游离钙浓度和环磷酸腺苷含量明显增加,在调节下丘脑神经元激活过程中下丘脑合成和分泌的促肾上腺皮质激素释放激素可能起了重要作用。

Regulative effect of corticotropin-releasing hormone on the concentration of cytoplasmic cyclic adenosine monophosphate and Ca2+in hypothalamic neuron

BACKGROUND: The activation of hypothalamus-pituitary-adrenal cortex axis may play key role in the increasing expression of hypothalamic corticotropin-re-leasing hormone (CRH) during stress reaction. However by what way to induce the CRH expression in hypothalamic neuron, and whether CRH can activate hypothalamic neurons are still not very clear.OBJECTIVE: To observe the changes of intracellular cyclic adenosine monophosphate (cAMP) and cytoplasmic Ca2+ concentration in the hypothalamic neurons cultured in vitro due to exogenous CRH stimulation.DESIGN: Comparative observation experiment.SETTING: Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA; Department of Neurosurgery , Tiantan Hospital, Capital University of Medical Sciences MATERIALS: This experiment was carried out in the Research Institute of Surgery, Daping Hospital, Third Military Medical University of Chinese PLA between December 1999 and March 2002. Hypothalamus was obtained from fetus rat at pregnancy of 17 days for the in vitro culture of hypothalamic neurons.METHODS: Hypothalamic neurons were co-cultured with exogenous CRH,with or without pretreatment with specific CRH 1 receptor antagonist -CP-154526. hypothalamic neurons were randomized into: ① CRH (10-12,10-10, 10-8, 10-6 mol/L) stimulation group. ② CP-154526(500 μmol/L)pretreatment aud CRH ( 10-12, 10-10, 10-8,10-6 mol/L) stimulation group. ③Hypothalamic neurons in corresponding normal control group were exposed to the isotonic saline stimulation. PTI fluorescence image system was used to determine and analyze the change of cytoplasmic free Ca2+ concentration in hypothalamic neurons due to exogenous CRH stimulation and RIA was used to detect the neuronal cAMP content.MAIN OUTCOME MEASURES: ①Cytoplasmic free Ca2+ concentration in hypothalamic neurons. ②cAMP content in hypothalamic neurons.RESULTS: The cytoplasmic free Ca2+ concentration and cAMP content were relatively lower in the hypothalamic neurons in normal control group,which obviously increased due to CRH stimulation [(240±22),(153±11)nmol/L; (3.26±0.19),(0.44±0.02) pmol/dish,P ＜ 0.01];CP-154526 could remarkably suppress the CRH (10-6 mol/L)induced increase in cytoplasmic free Ca2+ concentration and cAMP content in hypothalamic neurons [Ca2+ concentration: (240±22),(171±16)nmol/L; cAMP content:(3.26±0.19), (2.33±0.21) pmol/dish, P ＜ 0.01].CONCLUSION: CRH can directly act on hypothalamic neurons via type 1-receptor,thereby increase the cytoplasmic free Ca2+ concentration and cAMP content in hypothalamic neurons,playing the key role in the modulation of the synthesis and secretion of CRH during the activation of hypothalamic neurons.