Regulative effect of corticotropin-releasing hormone on the concentration of cytoplasmic cyclic adenosine monophosphate and Ca2+in hypothalamic neuron / 中国组织工程研究

ABSTRACT

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.