游泳应激对下丘脑室旁核CRH/AVP基因转录的影响及糖皮质激素的作用

Effect of Swim Stress on CRH/AVP Gene Transcription and the Role of Glucocorticoid

目的阐明游泳应激后下丘脑室旁核(PVN)促肾上腺皮质激素释放激素(CRH)和血管加压素(AVP)基因转录的变化以及非生理剂量地塞米松对两基因转录的调节作用。方法生理盐水(100μl)或地塞米松(0.3mg/kg)腹腔内注射2h后,强迫游泳10min分别立即断头取血;血中促肾上腺皮质激素(ACTH)水平应用放射免疫分析法(RIA)测定。合成[35S]标记的RNA探针,应用原位杂交组织化学方法及放射自显影的方法检测CRH mRNA、CRH hnRNA、AVP mRNA及AVP hnRNA的表达量,放射自显影图像应用NIH Image软件系统解析。所有数据均输入数据库,以statview软件进行统计分析。结果强迫游泳10min血中的ACTH明显升高,而地塞米松可部分抑制这种由于游泳应激引起的血中ACTH升高。游泳应激10min时PVN内的CRH hnRNA表达量明显升高,地塞米松的投与完全抑制了CRH hnRNA的增加(P<0.01,n=5)。在单纯生理盐水和地塞米松注射组PVN小细胞内AVP hnRNA的表达量极少,游泳应激10min小细胞内AVP hnRNA的表达量无明显变化,地塞米松对此也无任何影响。结论糖皮质激素可以抑制急性应激所致的CRH基因转录。与此不同的是强迫游泳应激后PVN小细胞区AVP基因转录水平却并未立即增加,说明虽然AVP与CRH基因均表达于PVN区同一神经元,但是其转录调控机制却不尽相同。

Objective To elucidate the transcriptional variety of corticotropin releasing hormone （CRH） and arginine vasopressin （AVP） gene after swim stress in the paraventricular nucleus （PVN） of rat hypothalamus, and to examine the effect of large-dose glucocorticoid on CRH/AVP gene transcription induced by swim stress. Methods Two hours after the injection of saline （ 100 μl） or dexareethasone （0.3 mg/kg） into peritoneal cavity,the rats were forced to swim for 10 minutes and then decapitated. The ACTH level in the blood was detected by radioimmunological assay. The expressions of CRH mRNA,CRH hnRNA,AVP reRNA,and AVP hnRNA were detected by in situ hybridization histochemistry,using [35S]-labeled cRNA probes. All the data were analyzed by using StatView software. Results The ACTH level in the blood significantly increased after 10-minute swim stress, which was inhibited by dexamethasone in part. The expression of CRH hnRNA in PVN significantly increased after 10-minute swim stress,and this effect was completely inhibited by dexamethasone （P 〈 0.01 ,n = 5）. The expression of AVP hnRNA in PVN was low after the injection of saline or dexamethasone. No remarkable change in AVP hnRNA expression was found after 10-minute swim stress, and dexamethasone did not affect the expression of AVP hnRNA. Conclusion Glucocortieoid could inhibit CRH gene transcription induced by stress, but A VP gene transcription in PVN does not increase after swim stress, suggesting the regulatory mechanisms for these 2 genes were different although they are expressed in the same neuron of PVN.