生理学报Acta Physiologica Sinica, June 25 2003 55(3)

研究论文

代谢型谷氨酸受体阻断剂α-methyl-(4-tetrazolyl-phenyl) glycine对大鼠海马脑缺血耐受诱导的影响

冯荣芳, 李文斌*, 刘惠卿, 李清君, 陈晓玲, 周爱民, 赵红岗, 艾洁

河北医科大学基础医学研究所病理生理学研究室, 石家庄 050017

摘要: 实验采用大鼠四血管闭塞全脑缺血模型, 用硫堇染色法和胶质纤维酸性蛋白(GFAP)免疫组化法, 观察右侧脑室内注射Ⅱ型代谢型谷氨酸受体(metabotropic glutamate receptor 2/3, mGluR2/3)阻断剂α-methyl-(4-tetrazolyl-phenyl)glycine (MTPG)对海马CA1区神经元缺血耐受(BIT)诱导的影响, 以探讨mGluR2/3在BIT诱导中的作用。54只大鼠椎动脉凝闭后分为5组: (1)假手术组(n=8): 游离双侧颈总动脉, 但不夹闭; (2)单纯缺血组(n=8): 夹闭双侧颈总动脉8 min; (3)缺血预处理组(n=8): 夹闭双侧颈总动脉3 min作为脑缺血预处理(CIP), 再灌注24 h后再行夹闭8 min; (4) MTPG+缺血预处理组(n=22): CIP前20 min右侧脑室注射MTPG, 其余步骤同缺血预处理组; MTPG的剂量分别为0.4、0.2、0.04和0.008 mg, 以观察其剂量效应关系; (5) MTPG+单纯缺血组(n=8): 右侧脑室注射MTPG 0.2 mg 24 h后, 夹闭双侧颈总动脉8 min。所有动物均在手术后或末次缺血后7 d处死, 取材观察。结果如下: (1) 与假手术组相比, 单纯8 min缺血组海马CA1区组织学分级升高、锥体神经元密度降低, GFAP阳性表达增加(P<0.05); (2) 缺血预处理组的组织学分级、神经元密度及GFAP表达与假手术组相似, 未见单纯缺血组的上述变化, 表明CIP可防止后续8 min缺血造成的神经元损伤; (3) MTPG+缺血预处理组海马CA1区组织学分级明显增加、锥体神经元密度降低, 并且GFAP表达也明显增加(P<0.05), 这种变化与MTPG的剂量呈明显正相关, 表明CIP对神经元的保护作用可被MTPG阻断。(4) MTPG+单纯缺血组海马CA1区组织学分级和神经元密度以及GFAP的表达与单纯缺血组相似。上述结果提示, 3 min CIP 可诱导BIT的形成, MTPG可阻断CIP诱导BIT的作用, 表明mGluR 2/3参与BIT的诱导。

关键词: 脑预缺血处理; 代谢型谷氨酸受体; α-甲基-(4-四唑基-苯)甘氨酸; 脑缺血耐受; 海马

中图分类号: Q426; R338

Effects of α-methyl-(4-tetrazolyl-phenyl) glycine on the induction of hippocampal ischemic tolerance in the rat

FENG Rong-Fang, LI Wen-Bin*, LIU Hui-Qing, LI Qing-Jun, CHEN Xiao-Ling, ZHOU Ai-Min,

ZHAO Hong-Gang, AI Jie

Department of Pathophysiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang 050017

Abstract: To explore the role of metabotropic glutamate receptor 2/3（mGluR 2/3）in the induction of brain ischemic tolerance (BIT), the influences of mGluR2/3 antagonist α-methyl-(4-tetrazolyl-phenyl) glycine (MTPG) on the induction of BIT and expression of glial fibrillary acidic protein (GFAP) in the hippocampus were observed using thionin staining and GFAP immunohistochemical staining in a rat brain ischemic model with four-vessel occlusion (4VO). Fifty-four rats, of which bilateral vertebral arteries were occluded permanently by electrocautery, were divided into 5 groups: (1) sham operated group (n=8): the bilateral carotid common arteries (BCCA) were separated, but the blood flow was not blocked; (2) ischemia group (n=8): the blood flow of BCCA was blocked for 8 min; (3) ischemic preconditioning (IP) group (n=8): the blood flow of BCCA was occluded for 3 min as a cerebral ischemic preconditioning (CIP), and then the rats were exposed to an 8-min brain ischemic insult 24 h after the CIP; (4) MTPG+IP group (n=22): MTPG was administered 20 min before the CIP, then the rats were exposed to an 8-min brain ischemia insult 24 h after the CIP . In order to examine dosage dependency in the effect of MTPG, 4 dosages of MTPG (0.4, 0.2, 0.04 and 0.008 mg) were administered; (5) MTPG+ischemia group (n=8): an ischemic insult for 8 min was given 24 h after the administration of MTPG (0.2 mg). MTPG was injected into the right lateral cerebral ventricle. The results obtained are as follows. (1) Ischemic insult for 8 min increased the histological grade (HG) and reduced the neuronal density (ND) significantly, and also increased the expression of GFAP significantly (P<0.05 vs sham-operated group). (2) In the IP group, the above changes were not observed, indicating that CIP could protect pyramidal neurons against the ischemic insult. (3) The protective effects of CIP were blocked by MTPG, as manifested by the significant increase in HG and decrease in ND in the MTPG+IP group (P<0.05 vs sham-operated group). The changes were dose-dependent . (4) No obvious difference in the HG, ND and expression of GFAP was detected between the groups of MTPG+ischemia and ischemia. The above results indicate that MTPG blocks the induction of BIT induced by CIP, suggesting that mGluR2/3 participates in the induction of BIT.

Key words: cerebral ischemic preconditioning; metabotropic glutamate receptors; α-methyl-(4-tetrazolyl-phenyl)glycine; brain ischemic tolerance; hippocampus