急性脑缺血大鼠边缘系统谷氨酸及其受体对下丘脑-垂体-肾上腺轴的影响

Effects of glutamate, glutamate receptor in limbic system and hypothalamus on hypothalamus pituitary adrenal axis after rats MCAO

目的观察脑缺血／再灌流过程中海马和下丘脑的谷氨酸、谷氨酸受体（ＧｌｕＲ）的变化特征及其对下丘脑－垂体－肾上腺轴（ＨＰＡ）活动的影响。方法应用高效液相色谱、受体的放射配体结合分析、核酸原位杂交、放射免疫分析分别监测大脑中动脉闭塞大鼠海马和下丘脑的谷氨酸含量、促皮质释放激素（ＣＲＨ）信使核糖核酸（ｍＲＮＡ）表达水平、血浆促肾上腺皮质激素（ＡＣＴＨ）浓度变化。结果动脉闭塞１５分钟，下丘脑、海马两部位的谷氨酸含量迅速增加，缺血１小时达高峰，复流后迅速回落至基线水平；再灌流２４小时再次中度升高，并持续至４８小时后缓慢回降。缺血期海马、下丘脑的ＧｌｕＲ下调，再灌流期呈现典型的上向同种特异性正向调节。缺血１小时颞皮质，海马、下丘脑等区ＣＲＨｍＲＮＡ表达明显活跃，并持续至再灌流９６小时，血浆ＡＣＴＨ浓度同步升高。再灌流损伤高峰期下丘脑谷氨酸含量与ＣＲＨｍＲＮＡ阳性表达细胞数、血浆ＡＣＴＨ浓度间均呈显著正相关。结论谷氨酸参与了急性脑缺血特定条件下ＨＰＡ的异常活动。

Objective To investigate the features of activity changes of glutamate(Glu), glutamate receptors(GluR) in hippocampus and hypothalamus during rats middle cerebral artery occlusion (MCAO) or reperfusion. Methods Using radio legend binding assay of receptor (RBA),high performance liquid chromatography (HPLC) and hybridization in situ and radioimmunometric assay, (RIA), we determined the dynamic changes of Glu content,GluR capacity and it′s Kd in cell membrane from the hippocampus of the ischemic brain and the hypothalamus CRHmRNA expression levels in every brain areas and ACTH concentrations in plasma at different time after middle cerebral artery occlusion(MCAO) or reperfusion. Results Glu content rapidly increased in the hippocampus and the hypothalamus at 15 minutes after MCAO, and reached the peak values at I 1h , and rapidly decreased to the basic line level after reperfusion. Glu content IR 24h to IR 48h , was elevated again moderately , and declined slowly 48 hours after reperfusion. The GluR was down regulated and the affinity enhanced in during the ischemic period. During the reperfusion period, the GluR was typically up regulated. The CRHmRNA expressive levels were markedly enhanced in the tempol cortex, the hippocampus and the hypothalamus atI 1h ,and kept to IR 96h ,the ACTH concentration in the plasma increased relatively. In the peak time of reperfusion,the Glu content of hypothalamus was positively corrected with CRHmRNA expressive positive cell amounts of the hypothalamus. Conclusion CRH may aggravate ischemic neuronal damage, and Glu participates in the pathogenesis of HPA axis be excited strongly and may be an important impel factor for ACI specially condition.