代谢型谷氨酸受体1亚型选择性拮抗剂LY367385对抗大鼠缺血性脑水肿

目的研究代谢型谷氨酸受体1亚型（mGluR1）选择性拮抗剂LY367385对大鼠缺血性脑水肿的影响.方法Wistar雄性大鼠（280～320g）线栓法复制大脑中动脉闭塞（MCAO）脑缺血模型.动物随机分为生理盐水（NS）对照组、LY367385给药组及MK-801给药组,于MCAO后1min,侧脑室内注射NS或LY367385（500nmol）5μl,或腹腔注射MK-801（1mg/kg）.各组动物分别于MCAO 6、24h进行神经病学评分、脑含水量测定及脑梗死面积测定.结果LY367385明显改善大鼠脑缺血引起的神经症状,而MK-801在MCAO 6h增加神经病学评分.LY367385降低大鼠MCAO引起的脑含水量增加,MK-801无明显作用.LY367385及MK-801均降低脑梗死面积百分率,且LY367385作用优于MK-801.结论LY367385能对抗大鼠脑缺血性脑水肿,作用明显优于MK-801.     

细胞外信号调节激酶在蛛网膜下腔出血损伤中的作用及意义

目的研究细胞外信号调节激酶(ERK)途径在蛛网膜下腔出血(SAH)脑损伤中的作用。方法ICR小鼠随机分为假手术组、模型组、U0126干预组,采用非开颅血管内穿线法制备小鼠SAH模型,给予ERK抑制剂U0126,术后行颅底检查,分别在SAH后12、24、48h 3个时相点取右侧大脑动脉标本,在光镜下观察大脑中动脉病理变化,应用免疫印迹法检测各组p-ERK1/2、caspase-8蛋白表达,TUNEL法检测大脑中动脉内皮细胞凋亡。结果随损伤时间延长,模型组小鼠p-ERK1/2、caspase-8蛋白均有不同程度增强,凋亡细胞增多。与模型组比较,U0126干预组小鼠各时相点3项指标的表达均不同程度下调。结论 ERK信号途径参与小鼠SAH病理损伤过程,并在神经细胞凋亡进程中发挥关键作用。     

巴豆生物碱通过ERK1/2通路对脑缺血再灌注大鼠海马神经元损伤及自噬的影响

目的 探讨巴豆生物碱(Croton alkaloids,CA)通过细胞外调节蛋白激酶1/2(Extracellular signal regulated kinase1/2,ERK1/2)通路对脑缺血再灌注大鼠海马神经元损伤及自噬的影响。方法 50只大鼠建立大脑中动脉闭塞(Middle cerebral artery occlusion,MCAO)再灌注模型,造模成功大鼠(48只),并随机分为模型组(12只)、CA低剂量组(12只)、CA中剂量组(12只)和CA高剂量组(12只),其余10只为对照组; CA低、中和高剂量组分别注射0.6、1.2、2.4 mg/kg的CA注射液,连续注射7 d; 对照组及模型组给予等量生理盐水注射; 应用神经功能评分法评定大鼠神经功能缺损和改善情况; 苏木精-伊红染色法(Hematoxylin eosin staining,HE)检测大鼠脑组织海马神经元的形态及数量; 原位末端转移酶标记法(Terminal uridine nick end labeling,TUNEL)检测大鼠脑组织细胞凋亡; 实时荧光定量聚合酶链反应(Real time quantitative PCR,RT-qPCR)和免疫印迹法(Western blot)检测各组大鼠海马ERK1/2、哺乳动物同源蛋白(Mammalian homologous protein,Beclin-1)、微管相关蛋白1轻链3(Microtubule-associated protein 1 light chain 3,LC3-Ⅱ)mRNA和蛋白表达水平。结果 与模型组比较,CA低、中、高剂量组神经功能评分、p-ERK1/2蛋白表达水平提高,神经细胞凋亡率、Beclin-1,LC3-Ⅱ mRNA和蛋白表达水平下降(P<0.05); 与CA低剂量组比较,CA中、高剂量组神经功能评分、p-ERK1/2蛋白表达水平提高,神经细胞凋亡率、Beclin-1,LC3-Ⅱ mRNA和蛋白表达水平下降(P<0.05); 与CA中剂量组比较,CA高剂量组神经功能评分、p-ERK1/2蛋白表达水平提高,神经细胞凋亡率、Beclin-1,LC3-Ⅱ mRNA和蛋白表达水平下降(P<0.05)。结论 CA可降低MCAO大鼠神经细胞凋亡率,在一定程度上修复MCAO大鼠神经功能,发挥神经保护作用,其机制可能与激活ERK1/2信号通路有关。     

Caspr敲除在蛛网膜下腔出血早期脑损伤机制的实验研究

目的 探讨黏连蛋白相关蛋白(Caspr)敲除对小鼠蛛网膜下腔出血(SAH)后早期脑损伤(EBI)的影响及其可能的作用机制。方法 采用C57BL/6小鼠及Caspr敲除(Caspr^+/-)小鼠,共分为4组：SAH模型组、假手术组、Caspr^+/-+SAH模型组和Caspr^+/-组,采用视交叉前池注血法建立SAH模型。SAH发生24 h后进行神经功能评分和脑水肿检测。采用Western Blot和ELISA法检测Caspr、B淋巴细胞瘤-2基因(Bcl-2)、Bax、Caspase-1、白细胞介素1β(IL-1β)和IL-18的表达;采用TUNEL染色法观察SAH后神经元的凋亡。结果 Caspr敲除导致Bcl-2表达下降,Bax、Caspase-1、IL-1β和IL-18表达升高,促进神经元凋亡。结论 Caspr敲除通过激活神经细胞凋亡加重SAH后的EBI。     

低聚体原花青素对实验性SAH大鼠早期脑损伤的保护作用研究

目的探讨低聚体原花青素(OPC)对实验性蛛网膜下腔出血(SAH)大鼠早期脑损伤的影响。方法 160只大鼠随机分为假手术对照组、SAH+生理盐水(NS)组,以及SAH+低剂量(50μg/kg)、中剂量(100μg/kg)、高剂量(200μg/kg)OPC组。采用视交叉池注血法建立SAH大鼠模型,分别给予不同剂量OPC或NS侧脑室注射治疗。术后24 h,检测各组大鼠的神经功能评分、脑含水量(干湿重法)、凋亡蛋白表达(Western blot)、细胞凋亡和炎症因子水平。结果与对照组比较,SAH大鼠脑组织含水量、活性氧(ROS)水平及颞叶皮层细胞凋亡蛋白表达水平、细胞凋亡数和炎症因子水平均明显增加。而经OPC治疗大鼠的这些指标水平均有明显降低,以及早期脑损伤症状有所缓解。结论 OPC可以减轻SAH后的早期脑损伤,可能与其抗氧化、抗炎和抗凋亡作用有关。     

脑源性神经营养因子对脑梗死大鼠神经细胞凋亡及Bcl-2、Bax蛋白表达的影响

目的 探讨侧脑室内立体定向注射脑源性神经营养因子(BDNF)对脑梗死大鼠神经细胞凋亡及Bcl-2、Bax蛋白表达的影响.方法 32只SD大鼠成功制作大脑中动脉闭塞模型,随机分为BDNF组(n=16)和对照组(n=16),在两组大鼠侧脑室内分别注射10μ1 BDNF溶液(0.5 μmol)和10μl磷酸盐缓冲液(PBS液).注射2周后,2组大鼠分别行神经功能严重性评分(mNSS)及梗死面积测定,应用免疫组化染色、Western blot分析脑组织Bcl-2、Bax蛋白的表达,Tunel检测细胞凋亡.结果 与对照组比较,BDNF组脑梗死面积缩小,神经细胞凋亡数少,Bax蛋白表达低,Bcl-2蛋白表达高,短期内神经功能恢复好,差异均具有统计学意义(P＜0.05).结论 BDNF可能通过调节Bcl-2、Bax蛋白表达,减少神经细胞凋亡,改善脑缺血大鼠的功能.     

天麻素注射液对蛛网膜下腔出血大鼠NF-κB/Bax/Caspase-3通路及神经元凋亡的影响

目的 探讨天麻素注射液对蛛网膜下腔出血(Subarachnoid hemorrhage,SAH)大鼠核转录因子-κB/B细胞淋巴瘤-2基因相关X蛋白/半胱氨酸天冬氨酸蛋白水解酶-3(Nuclear factor-κB,NF-κB/B cell lymphoma-2 associated X protein,Bax/Cysteinyl aspartate specific proteinase-3,Caspase-3)通路及神经元凋亡的影响。方法 血管穿刺法建立SAH大鼠模型,模型成功50只,随机分为模型组、天麻素低、中、高剂量组(腹腔注射5、10、20 mg·kg^-1·d^-1天麻素注射液)、阳性对照组(腹腔注射0.5 mg·kg^-1·d^-1地塞米松磷酸钠注射液),每组各10只,另10只大鼠设为假手术组; 干预3周后测定大鼠神经功能评分; 流式细胞术检测脑皮层细胞凋亡情况; 原位末端标记法(TdT-mediated dUTP-biotin nick end labeling assay,TUNEL)检测神经元凋亡状态; 蛋白免疫印迹(Western blot,WB)检测大鼠脑皮层NF-κB,Bax,Caspase-3、生长相关蛋白-43(Growth-associated protein-43,GAP-43)、突触素(Synaptophysin,SYN)蛋白表达水平。结果 与假手术组比较,模型组神经功能评分、脑皮层神经元凋亡率、脑组织中NF-κB,Bax,Caspase-3蛋白表达水平升高,脑皮层组织中GAP-43,SYN蛋白表达水平降低(P<0.05)。与模型组比较,天麻素中、高剂量组、阳性对照组神经功能评分、脑皮层神经元凋亡率、脑组织中NF-κB,Bax,Caspase-3蛋白表达水平降低,脑皮层组织中GAP-43,SYN蛋白表达水平升高(P<0.05); 天麻素低剂量组脑皮层神经元凋亡率、脑组织中NF-κB,Bax,Caspase-3蛋白表达水平降低,脑皮层组织中GAP-43,SYN蛋白表达水平升高(P<0.05); 随着天麻素注射液剂量的升高,神经功能评分、脑皮层神经元凋亡率、脑组织中NF-κB,Bax,Caspase-3蛋白表达水平降低,脑皮层组织中GAP-43,SYN蛋白表达水平升高(P<0.05)。结论 天麻素注射液可能通过抑制NF-κB/Bax/Caspase-3通路来实现对神经元凋亡的缓解和对SAH大鼠的脑保护。     

辛伐他汀对蛛网膜下腔出血早期脑损伤大鼠NLRP3炎性小体的表达及NF-κB信号通路的影响

目的 探究辛伐他汀(simvastatin)对蛛网膜下腔出血(SAH)早期脑损伤(EBI)大鼠NLRP3的表达及NF-κB信号通路的影响。方法 100只大鼠随机分为假手术(Sham)组、SAH组、Simvastatin组、NF-κB信号通路抑制剂(PJ34)组,每组25只。视交叉前池注血法构建SAH模型,建模后2h给药,Simvastatin组、PJ34组腹腔注射辛伐他汀和PJ34,另外两组腹腔注射等体积生理盐水。1次·d^-1,连续14 d。给药结束24 h后,采用Garcia评分评估造模后大鼠的神经功能;Sugawara出血量评分评价脑组织出血情况;苏木精-伊红染色、透射电镜观察脑组织病理变化与超微结构损伤;测定脑组织含水量;TUNEL染色、ELISA、免疫组化分别检测细胞凋亡情况、炎症因子表达水平与NLRP3表达情况;Western blotting检测脑组织NLRP3、Caspase-1、核因子-κB (NF-κB-p65)的表达水平。结果 与SAH组相比,Simvastatin组SAH、炎性浸润明显减轻,脑组织病理损伤明显改善,脑组织含水量、神经细胞凋亡、...     

褪黑激素抑制NLRP3炎性小体减轻小鼠蛛网膜下腔出血早期脑损伤

目的探讨褪黑素通过调节核苷酸结合寡聚化结构域样受体3炎症复合体(NLRP3)对蛛网膜下腔出血(SAH)后早期脑损伤(EBI)的保护作用和机制。方法建立小鼠颈动脉线穿法SAH模型,分为假手术组、假手术+溶剂组、SAH+溶剂组和SAH+褪黑素组四组,进行SAH出血量评级和小鼠神经功能缺陷评分,脑组织水含量测定脑水肿,伊文思蓝法测定血脑屏障(BBB)通透性,检测脑丙二醛(MDA)和谷胱甘肽(GSH)水平,神经核抗原(Neu N)和末端脱氧核苷酸转移酶介导的d UTP缺口末端标记测定法(TUNEL)检测神经元存活和死亡率,Western Blot检测脑凋亡相关斑点样蛋白(ASC)、白细胞介素-1β(IL-1β)、核苷酸结合寡聚化结构域样受体3炎症复合体(NLRP3)、B淋巴细胞瘤-2基因(Bcl2)、前凋亡因子(Bim)和活化的caspase-1蛋白表达,酶联免疫吸附测定(ELISA)脑中细胞因子白介素-1β(IL-1β)和白介素-6(IL-6)水平。结果槲皮素可以提高SAH小鼠生存率,降低神经功能缺陷评分,减少脑神经元凋亡,提高脑谷胱甘肽(GSH)水平,降低丙二醛(MDA)水平,减轻脑水肿和BBB通透性损害。槲皮素可以降低NLRP3以及细胞凋亡相关斑点样蛋白(ASC)的表达,抑制IL-1β、IL-6的分泌和活化的caspase-1的蛋白表达,并可以增高抗凋亡因子Bcl2的表达,降低凋亡前体因子Bim的表达。结论槲皮素通过抑制NLRP3炎性相关的凋亡来减轻SAH后的EBI。     

虾青素对小鼠蛛网膜下腔出血早期脑损伤的保护机制的研究

目的研究虾青素对小鼠蛛网膜下腔出血(SAH)早期脑损伤的保护机制。方法 ICR雄性小鼠采用随机数字法随机分为四组:蛛网膜下腔出血组、假手术组、蛛网膜下腔出血+溶剂组(DMSO)、蛛网膜下腔出血+虾青素组。通过建立小鼠视交叉注血方法建立蛛网膜下腔出血模型,于手术后24 h记录神经功能评分,并应用末端脱氧核苷酸转移酶介导的生物素脱氧尿嘧啶核苷酸缺口末端标记法(TUNEL)、western blot法检测脑组织中的NOX2蛋白含量、ELISA法检测TNF-a/IL-1β水平,干湿法检测脑组织中含水量。结果与对照组相比,SAH后小鼠神经功能损伤评分加重,脑水肿加重,脑组织中的NOX2蛋白及脑组织中凋亡阳性细胞数也显著增多,TNF-a/IL-1β值明显升高;应用虾青素干预以后,小鼠神经功能改善,脑组织凋亡阳性细胞明显减少。同时,虾青素能够降低SAH后小鼠脑组织中NOX2蛋白,TNF-a/IL-1β水平值也明显降低。结论虾青素对s AH后早期脑损伤(EBI)具有保护作用,其作用机制可能与其抗氧化性有关。     

Pharmacological antagonism of metabotropic glutamate receptor 1 regulates long-term potentiation and spatial reference memory in the dentate gyrus of freely moving rats via N-methyl-D-aspartate and metabotropic glutamate receptor-dependent mechanisms

Group I metabotropic glutamate receptors (mGluRs) are critically required for multiple forms of hippocampal synaptic plasticity in vivo. The role of the receptor subtype mGluR1 in long-term potentiation (LTP) and learning is unclear. We examined the contribution of mGluR1 to hippocampal LTP and spatial learning using the selective antagonist (S)-(+)-alpha-amino-4carboxy-2-methylbenzene-acetic acid (LY367385). Male Wistar rats were chronically implanted with recording and stimulating electrodes to enable measurement of evoked potentials from medial perforant path-dentate gyrus granule cell synapses. An injection cannula was inserted into the ipsilateral cerebral ventricle to enable drug application. Experiments were begun 10 days after the implantation procedure. We induced a robust LTP which lasted over 25 h with a 200-Hz tetanization. Injections of LY367385 at all concentrations under investigation (4-32 nmol in a 5-microL injection volume) did not affect basal synaptic transmission. In contrast, we observed a dose-dependent impairment of LTP expression: LY367385 (4 nmol) had no effect on LTP induction, whereas 8 and 16 nmol LY367385 reduced both LTP induction and expression, suggestive of an interaction with N-methyl-d-aspartate receptors. We assessed the effects of daily LY367385 application (8 nmol) on performance in an eight-arm radial maze. LY367385-treated rats showed deficits in reference but not working memory performance compared with vehicle-treated controls. Rearing, grooming and locomotor activity were unaffected by LY367385. These data suggest an important role for mGluR1 in LTP and learning and highlight the specific significance of this mGluR subtype for reference memory.     

Selective blockade of the mGluR1 receptor reduces traumatic neuronal injury in vitro and improvesoOutcome after brain trauma

The effects of selective blockade of group I metabotropic glutamate receptor subtype 1 (mGluR1) on neuronal cell survival and post-traumatic recovery was examined using rat in vitro and in vivo trauma models. The selective mGluR1 antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), and (S)-(+)-alpha-amino-4-carboxy-2-methylbezeneacetic acid (LY367385) provided significant neuroprotection in rat cortical neuronal cultures subjected to mechanical injury, in both pretreatment or posttreatment paradigms. Administration of the antagonists also attenuated glutamate-induced neuronal cell death in the cultures. Coapplication of these antagonists with the N-methyl-d-aspartate (NMDA) receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) had additive neuroprotective effects in glutamate injured cultures. Intracerebroventricular administration of AIDA to rats markedly improved recovery from motor dysfunction after lateral fluid percussion induced traumatic brain injury (TBI). Treatment with mGluR1 antagonists also significantly reduced lesion volumes in rats after TBI, as evaluated by MRI. It appears that these compounds mediate their neuroprotective effect through an mGluR1 antagonist action, as demonstrated by inhibition of agonist induced phosphoinositide hydrolysis in our in vitro system. Moreover, AIDA, CPCCOEt, and LY367385, at concentrations shown to be neuroprotective, had no significant effects on the steady state NMDA evoked whole cell current. Taken together, these data suggest that modulation of mGluR1 activity may have substantial therapeutic potential in brain injury.     

The metabotropic glutamate receptor 5 is necessary for late-phase long-term potentiation in the hippocampal CA1 region

Selective antagonists of the metabotropic receptors 1 (mGluR1), +/-2-methyl-4-carboxyphenylglycine (LY367385), and mGluR5, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), were used to investigate the role of group I metabotropic receptors in late-phase long-term potentiation (L-LTP) at Schaffer collateral/commissural fiber-CA1 synapses in rat hippocampal slices. L-LTP was induced with three trains of tetanization of 1 s duration at 100 Hz separated by 10-min intervals. Neither LY367385 nor MPEP affected basal synaptic responses at the doses used (200 and 10 microM, respectively) and only the mGluR5 inhibitor MPEP blocked L-LTP. However, in agreement with previous mouse mutant studies, we found that both LY367385 and MPEP inhibited the induction of an LTP obtained with a single train of tetanization of 1 s duration at 100 Hz. MPEP's ability to disrupt L-LTP was not due to an effect on NMDA responses since it did not affect pharmacologically isolated N-methyl-D-aspartate (NMDA) excitatory postsynaptic potentials (EPSPs). However, MPEP prevented the increased phosphorylation in dendrites of p70 S6 kinase (p70(S6K)) at Thr3889, a major regulator of translation required for the induction of protein synthesis-dependent forms of LTP.     

Selective Blockade of the mGluR1 Receptor Reduces Traumatic Neuronal Injury in Vitro and Improves Outcome after Brain Trauma

The effects of selective blockade of group I metabotropic glutamate receptor subtype 1 (mGluR1) on neuronal cell survival and post-traumatic recovery was examined using rat in vitro and in vivo trauma models. The selective mGluR1 antagonists (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), 7-(hydroxyimino)cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt), and (S)-(+)-α-amino-4-carboxy-2-methylbezeneacetic acid (LY367385) provided significant neuroprotection in rat cortical neuronal cultures subjected to mechanical injury, in both pretreatment or posttreatment paradigms. Administration of the antagonists also attenuated glutamate-induced neuronal cell death in the cultures. Coapplication of these antagonists with the N-methyl- -aspartate (NMDA) receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) had additive neuroprotective effects in glutamate injured cultures. Intracerebroventricular administration of AIDA to rats markedly improved recovery from motor dysfunction after lateral fluid percussion induced traumatic brain injury (TBI). Treatment with mGluR1 antagonists also significantly reduced lesion volumes in rats after TBI, as evaluated by MRI. It appears that these compounds mediate their neuroprotective effect through an mGluR1 antagonist action, as demonstrated by inhibition of agonist induced phosphoinositide hydrolysis in our in vitro system. Moreover, AIDA, CPCCOEt, and LY367385, at concentrations shown to be neuroprotective, had no significant effects on the steady state NMDA evoked whole cell current. Taken together, these data suggest that modulation of mGluR1 activity may have substantial therapeutic potential in brain injury.     

Melatonin decreases calcium levels in retinotectal axons of Xenopus laevis by indirect activation of group III metabotropic glutamate receptors

Melatonin is a neuromodulator that binds to receptors in the retinotectal laminae of the amphibian optic tectum. The effect of melatonin on calcium dynamics in Xenopus retinotectal axons was investigated by imaging retinotectal axons labeled with the fluorescent indicator Fluo-4. Melatonin exerted an inhibitory influence on depolarization-evoked calcium increases, and the melatonin receptor antagonist 4-P-PDOT blocked this effect. Blockade of group III metabotropic receptors (mGluRs) counteracted the effect of melatonin on retinotectal axons. Application of the group II/group III mGluR antagonist MSPG or the group III-selective antagonist MSOP abolished the effect of melatonin. Conversely, this effect was not significantly affected by the group I mGluR antagonist LY367385 nor by EGLU or LY341495 at concentrations that specifically inhibit group II mGluRs. Furthermore, a higher concentration of LY341495 that affects group III mGluRs inhibited the effect of melatonin. The data therefore support the hypothesis that, in retinotectal axons, melatonin reduces cAMP levels, thereby relieving PKA-induced inhibition of group III mGluRs; the newly activated mGluRs in turn inhibit voltage-sensitive calcium channels, leading to a decrease in Ca2+ concentrations. The role of GABA(C) receptors in retinotectal responses was also evaluated. GABA(C) receptor antagonists did not block the effects of melatonin but instead were additive. Moreover, while other studies have shown that in Xenopus tectal cells, GABA(C) receptors mediate inhibition, in retinotectal axons, the opposite appears to occur since depolarization-evoked calcium rises in retinotectal axons were inhibited by GABA(C) receptor blockade. This result suggests that activation of GABA(C) receptors produces an increase in the synaptic excitability of retinotectal axon terminals.     

Down-regulation of metabotropic glutamate receptor 1alpha in globus pallidus and substantia nigra of parkinsonian monkeys

Enhanced glutamatergic neurotransmission via the subthalamopallidal or subthalamonigral projection seems crucial for developing parkinsonian motor signs. In the present study, the possible changes in the expression of metabotropic glutamate receptors (mGluRs) were examined in the basal ganglia of a primate model for Parkinson's disease. When the patterns of immunohistochemical localization of mGluRs in monkeys administered systemically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were analysed in comparison with normal controls, we found that expression of mGluR1alpha, but not of other subtypes, was significantly reduced in the internal and external segments of the globus pallidus and the substantia nigra pars reticulata. To elucidate the functional role of mGluR1 in the control of pallidal neuron activity, extracellular unit recordings combined with intrapallidal microinjections of mGluR1-related agents were then performed in normal and parkinsonian monkeys. In normal awake conditions, the spontaneous firing rates of neurons in the pallidal complex were increased by DHPG, a selective agonist of group I mGluRs, whereas they were decreased by AIDA, a selective antagonist of group I mGluRs, or LY367385, a selective antagonist of mGluR1. These electrophysiological data strongly indicate that the excitatory mechanism of pallidal neurons by glutamate is mediated at least partly through mGluR1. The effects of the mGluR1-related agents on neuronal firing in the internal pallidal segment became rather obscure after MPTP treatment. Our results suggest that the specific down-regulation of pallidal and nigral mGluR1alpha in the parkinsonian state may exert a compensatory action to reverse the overactivity of the subthalamic nucleus-derived glutamatergic input that is generated in the disease.     

银杏内酯对脑淋巴阻滞后蛛网膜下腔出血大鼠脑水肿和神经元超微结构的影响

目的 探讨脑淋巴引流阻滞对大鼠蛛网膜下腔出血（subarachnoid hemorrhage,SAH）后脑水肿、海马神经元超微结构的影响及银杏内酯（Ginkgolide,Gl）对其的保护作用。方法 成年雄性Wistar大鼠90只,采用枕大池内新鲜自体动脉血二次注入法建立大鼠SAH模型,用颈淋巴管结扎和颈淋巴结摘除法制作大鼠脑淋巴引流阻滞（cerebral lymphatic blockade,CLB）模型。将动物随机分为：正常对照组;SAH组;CLB＋SAH组;CLB＋SAH＋生理盐水（NS）组;CLB＋SAH＋20mg/kg银杏内酯（Ginkgolides,Gl20）组;CLB＋SAH＋80mg/kg银杏内酯（Gl80）组。在建立SAH模型24h和72h后测定脑组织含水率;72h后用透射电镜观察神经元超微结构。结果 SAH组脑组织含水率较正常组增加;CLB＋SAH组脑组织含水率增加最为明显;与CLB＋SAH组比较,脑组织含水率在CLB＋SAH＋Gl20、CLB＋SAH＋Gl80两组均明显降低,其中CLB＋SAH＋Gl80组脑组织含水率降低明显。除对照组以外,神经元超微结构均有不同程度的损伤,CLB＋SAH组损伤较严重。结论 脑淋巴引流途径对大鼠SAH后脑组织水肿及海马神经元超微结构有重要影响;银杏内酯可降低脑淋巴阻滞后SAH大鼠的脑组织含水率,对海马神经元具有保护作用。     

Neuroprotection against NMDA excitotoxicity by group I metabotropic glutamate receptors is associated with reduction of NMDA stimulated currents

The neurotransmitter glutamate can have both excitotoxic and protective effects on neurons. The excitotoxic effects have been intensively studied, whereas the protective effects, including the involvement of metabotropic glutamate receptors (mGluRs), remain unclear. In the present study, we tested the protective effects of the group-I-mGluR agonist (S)-3,5-dihydroxyphenylglycine (DHPG) on organotypic hippocampal slice cultures exposed to excitotoxic concentrations of N-methyl-D-aspartate (NMDA). Effects of DHPG on electrophysiological responses induced by NMDA receptor activation were also recorded. Experiments were performed on organotypic hippocampal slice cultures derived from 7-day-old rats, with cellular uptake of propidium iodide as a marker for neuronal cell death. Slice cultures pretreated with DHPG (10 or 100 microM) for 2 h prior to exposure to 50 microM NMDA for 30 min displayed reduced propidium iodide uptake, compared to cultures exposed to NMDA only. The neuroprotective effect was confirmed by Hoechst 33342 staining, where the appearance of pycnotic nuclei after NMDA treatment was prevented by the DHPG pretreatment. Using caspase-3 activity to monitor the presence of apoptosis, failed to demonstrate this type of cell death in CA1 after NMDA application. The protective effect of DHPG was abolished by the mGluR1 selective antagonist (S)-(+)-alpha-amino-4-carboxy-2-methylbenzeneacetic acid (LY367385; 5 or 10 microM), whereas the mGluR5-selective antagonist 2-methyl-6-phenylethynylpyridine (MPEP; 1 microM) had no effect. Voltage-clamping of CA1 pyramidal cells in cultures treated with 10 microM DHPG for 2 h showed a significant depression of NMDA-induced inward currents compared to untreated controls. We conclude that neuroprotection induced by activation of group-I-mGluRs involve mGluR1 and is associated with decreased NMDA-stimulated currents.