苯环壬酯对N-甲基-D-天冬氨酸诱导的原代培养的大鼠海马神经细胞损伤的保护作用

目的　观察苯环壬酯对N 甲基 D 天冬氨酸(NMDA)诱导的原代培养大鼠海马神经细胞损伤的保护作用。方法　建立NMDA诱导的原代培养大鼠海马神经细胞损伤模型 ,采用乳酸脱氢酶 (LDH )法及噻唑蓝 (MTT)比色法 ,以特异性NMDA受体拮抗剂MK 80 1作为阳性对照药 ,观察抗胆碱药苯环壬酯、东莨菪碱对NMDA诱导的原代培养大鼠海马神经细胞损伤的保护作用。结果　NMDA (4 0 0μmol·L- 1)可明显降低海马神经细胞的存活率 ,表现为细胞LDH释放量明显增高 ,MTT比色后的吸光值明显降低。苯环壬酯 (1,2 .5 ,10 ,2 0和 5 0 μmol·L- 1)对NMDA所致的LDH升高有明显对抗作用 ,MTT比色后的吸光值明显增高 (P <0 .0 1) ,其作用类似于MK 80 1(1,10 μmol·L- 1) ;而另外一种抗胆碱药东莨菪碱 (1,10 ,10 0 0 μmol·L- 1)对损伤细胞的LDH释放及MTT比色后的吸光值无明显影响。结论　苯环壬酯对NMDA诱导的大鼠海马神经细胞损伤有明显保护作用 ,其作用机制可能与其对NMDA受体的拮抗作用有关     

苯环壬酯等抗胆碱药对不同致惊厥剂的对抗作用

目的　探讨苯环壬酯抗惊厥的作用是否与非胆碱能系统有关。方法　大鼠sc梭曼 180 μg·kg- 1,惊厥出现后不同时间 (5 ,2 0及 4 0min)ip不同剂量阿托品、东莨菪碱及苯环壬酯 ,观察上述药物的抗梭曼致惊疗效。小鼠ip阿托品 (1,5 ,10 ,2 0 ,4 0 ,6 0mg·kg- 1)、东莨菪碱 (1,5 ,10 ,2 0 ,4 0 ,6 0mg·kg- 1)及苯环壬酯 (1,4 ,8,16mg·kg- 1)后 30minsc戊四氮 95mg·kg- 1或ipN 甲基 D 天冬氨酸 (NMDA) 175mg·kg- 1。结果　随着惊厥的延续 ,阿托品、东莨菪碱的抗惊作用逐渐下降 ,并最终在惊厥发作后 4 0min完全消失 ;而苯环壬酯在惊厥发作后的各个阶段 (惊厥后 5 ,2 0 ,4 0min) ,特别是在惊厥发作后 4 0min ,ip苯环壬酯 (8mg·kg- 1)仍具有很好的抗惊作用。此外 ,上述抗胆碱药中 ,只有苯环壬酯 (4,8,16mg·kg- 1ip)可以显著对抗戊四氮所致的惊厥 ;6 ,8,12mg·kg- 1可拮抗致死剂量NMDA中毒。结论　不同于阿托品及东莨菪碱 ,苯环壬酯在梭曼所致惊厥后期仍有效 ,并可以对抗戊四氮所致惊厥及致死剂量NMDA中毒     

丁基苯酞对氯化钾及 N-甲基-D-门冬氨酸诱导的大鼠皮质神经细胞损伤的保护作用

用原代培养大鼠皮质神经细胞的方法,观察l-丁基苯酞(l-NBP)和d-丁基苯酞(d-NBP)对KCl及N-甲基-D-门冬氨酸(NMDA)诱导的大鼠皮质神经细胞损伤的保护作用。结果表明:l-NBP和d-NBP能剂量依赖性地抑制NMDA诱导的大鼠皮质神经细胞内乳酸脱氢酶的释放,降低细胞死亡率,改善受损细胞的形态;此外l-NBP和d-NBP还能明显减轻KCl诱导的神经细胞损伤。提示:l-NBP和d-NBP对KCl及NMDA诱导的大鼠皮质神经细胞损伤有明显保护作用。     

氟哌啶醇对大鼠离体海马脑片和原代神经元缺糖/缺氧和N-甲基-D-天冬氨酸损伤的保护作用

目的观察氟哌啶醇对大鼠离体海马脑片和原代神经元的缺糖/缺氧(OGD)和N-甲基-D-天冬氨酸(N-methyl-D-aspartate,NMDA)损伤的潜在保护作用及其机制。方法海马脑片OGD以无葡萄糖的人工脑脊液中通95% N₂+5% CO₂诱导。通过测定TTC染色后形成的红色产物来分析脑片活性。结果氟哌啶醇(1和10 μmol·L^-1)抑制OGD损伤,抑制率分别为17.7%和25%,而D₂多巴胺受体拮抗剂多潘立酮无此作用。NMDA也能显著降低海马脑片及原代神经元的活性,而氟哌啶醇可抑制这一损伤作用。结论氟哌啶醇对大鼠离体海马脑片OGD和原代神经元NMDA损伤有保护作用。     

大鼠海马注射胍基琥珀酸引起的惊厥及对神经细胞的损害作用

大鼠海马注射微量胍基琥珀酸,可引起典型的阵挛性惊厥和癫痫样放电,用高倍显微镜进行组织学分析发现,胍基琥珀酸能广泛损伤大鼠注射侧海马CA₁部位的锥体细胞。典型的抗癫痫药苯巴比妥和苯妥英钠不能对抗上述作用,而非竞争性NMDA受体的拮抗剂氯胺酮却有对抗作用,且能预防其对海马神经细胞的损害。结果提示,胍基琥珀酸在诱发惊厥和对神经细胞的损伤方面与兴奋性氨基酸 谷氨酸的作用非常相似。同时也说明,其作用与NMDA受体有一定的关系。     

盐酸苯环壬酯对大鼠后循环缺血性眩晕和小鼠位置性眩晕的改善作用

目的研究盐酸苯环壬酯的抗眩晕作用。方法利用双侧颈总动脉结扎法制备大鼠脑缺血模型,大鼠ig给予盐酸苯环壬酯0.1~4.0 mg·kg~(-1),每天2次,连续3 d,结合激光多普勒脑血流仪检测盐酸苯环壬酯对脑血流量变化的影响。通过XY-5双轴变速旋转刺激制备小鼠眩晕症模型,小鼠ig给予盐酸苯环壬酯1.4~5.6 mg·kg~(-1)后变速旋转刺激30 min,检测自发活动的变化;小鼠ig给予盐酸苯环壬酯1.4~8.4 mg·kg~(-1)30 min后,通过检测胃酚红排空率指标观察盐酸苯环壬酯对小鼠胃平滑肌的影响。结果大鼠双侧颈总动脉结扎24 h后脑血流量显著减少(P<0.01);与模型组比较,盐酸苯环壬酯0.5,2.0和4.0 mg·kg~(-1)可显著增加缺血大鼠脑血流量(P<0.05)。通过旋转刺激后,模型小鼠自发活动的总路程减少(P<0.05),运动速度减慢(P<0.05);与模型组比较,盐酸苯环壬酯2.8和5.6 mg·kg~(-1)可增加眩晕小鼠总路程和运动速度(P<0.05);盐酸苯环壬酯5.6和8.4 mg·kg~(-1)降低小鼠胃酚红排空率(P<0.05)。结论盐酸苯环壬酯增加脑血流量,改善后循环缺血,对眩晕的呕吐症状和运动功能具有显著的改善作用。     

人参皂甙Rb1和Rg1对原代培养大鼠海马神经细胞的保护作用

用大鼠海马神经细胞原代培养的实验模型,观察了人参皂甙Rb1和Rg1对原代培养的大鼠海马神经细胞生长的影响。结果发现Rb1和Rg1可明显延长培养神经细胞的存活时间、降低神经细胞的死亡率,并对抗谷氨酸介导的神经毒性作用。实验证明其机制在于选择性抑制大剂量谷氨酸引起的钙离子浓度异常升高。     

哇巴因预处理对模拟缺血大鼠海马神经元NMDA电流的影响

目的观察哇巴因预处理对模拟缺血大鼠海马神经元损伤的保护作用及其机制。方法采用原代培养的大鼠海马神经元,以全细胞膜片钳方法记录海马神经元NMDA电流（INMDA）。采用无糖无氧的方法模拟缺血灌流,建立神经元的体外急性缺血模型,观察模拟缺血对低浓度哇巴因预处理的海马神经元NMDA电流的影响。结果模拟缺血显著激活INMDA,低浓度哇巴因预处理可阻断模拟缺血对神经元INMDA的激活。结论模拟缺血可促进NMDA通道开放。哇巴因预处理能保护神经元抵抗由NMDA受体诱导的兴奋性神经毒性,此神经保护机制与哇巴因阻断缺血对NMDA受体的过度激活、缓解神经元Ca2＋超载密切相关。     

托吡酯对原代培养海马神经元癫痫样放电的抑制效应

目的:探讨托吡酯对原代培养海马神经元癫痫样放电的抑制作用及其特点。方法:分离原代培养 1日龄SD大鼠海马神经元,d9~15采用膜片钳全细胞模式记录托吡酯 ( 20, 100μmol·L-1 )和苯妥英 (10μmol·L-1 )对电流刺激及谷氨酸诱导神经元癫痫样放电的抑制效应。结果:苯妥英(10μmol·L-1 )、托吡酯(20, 100μmol·L-1 )抑制电流刺激诱导神经元动作电位,分别减少 100 %,(38±25) %和 ( 70±19 ) %。苯妥英 ( 10μmol·L-1 )及托吡酯(100μmol·L-1 )分别完全或部分抑制谷氨酸诱导海马神经元的癫痫样放电。结论:托吡酯抑制原代培养海马神经元的癫痫样放电,并与其浓度及作用时间有关。     

腺苷A1受体和NMDA受体在海马齿状回突触传递活动中的关系

目的探讨腺苷A₁受体阻断剂对海马齿状回(DG)突触传递活动的影响及其与NMDA受体的关系。方法 采用在体记录麻醉大鼠LTP的电生理学方法,观察腺苷A₁受体特异性阻断剂8-环戊-1,3-二丙基黄嘌呤(DPCPX)与NMDA受体激动剂、阻断剂在海马DG基础突触传递活动和高频刺激诱导的LTP中作用的相关性。结果DPCPX(6 mg·L^-1,5 μL,icv)或NMDA(0.2 mg·L^-1,5 μL,icv)不影响大鼠海马DG突触传递活动,DPCPX对icv NMDA后高频刺激诱导已形成的LTP维持也无影响;预先给予DPCPX后则可显著增强NMDA的海马DG基础突触传递活动和LTP;AP₅(0.5 mg·L^-1,5 μL)阻断NMDA受体后对LTP的抑制作用不受DPCPX的影响,但预先给予DPCPX则可取消AP₅对LTP的抑制作用。结论DPCPX不影响海马DG突触传递活动,但可影响NMDA受体的效应,增强NMDA受体在海马DG突触传递活动中的作用。     

Protective Effect of Gabapentin on N-methyl-D-aspartate–Induced Excitotoxicity in Rat Hippocampal CA1 Neurons

Gabapentin was developed as an anticonvulsant, but has also been used to alleviate hyperalgesia in neuropathic pain. In this study, the protective effect of gabapentin against N-methyl-D-aspartate (NMDA)-induced excitotoxicity in rat hippocampal CA1 neurons was investigated. Pre-treatment with gabapentin reduced the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices. Patch-clamp studies revealed that gabapentin significantly inhibited the NMDA receptor–activated ion current in dissociated hippocampal CA1 neurons, resulting in suppression of glutamate-induced neuronal injury. These results show that gabapentin may exert protective effects against glutamate-induced neuronal injury at least in part by inhibiting the NMDA receptor–activated ion current.     

Effects of GYKI 52466 and some 2,3-benzodiazepine derivatives on hippocampal in vitro basal neuronal excitability and 4-aminopyridine epileptic activity

In order to determine whether the anticonvulsant effect of 2, 3-benzodiazepines is also displayed in a model of in vitro epilepsy, such as the "epileptiform" hippocampal slice, we studied the effects of 2,3-benzodiazepine 1-(4-aminophenyl)-4-methyl-7, 8-methylenedioxe-5H 2,3-benzodiazepine hydrochloride (GYKI 52466) and some new 2,3-benzodiazepine derivatives on CA1 basal neuronal excitability and on CA1 epileptiform burst activity produced by 4-aminopyridine in rat hippocampal slices. The results showed that GYKI 52466 affected basal neuronal excitability as evidenced by its influence on the magnitude of the CA1 orthodromic-evoked field potentials. 2,3-Benzodiazepines showed their antiepileptic effect also in an in vitro model of experimental epilepsy. The effects of the new 2,3-benzodiazepine derivatives suggest that the methylenedioxidation in positions 7 and 8 of the 2,3-benzodiazepine ring is the main structural modification for the antiepileptic effect of 2,3-benzodiazepines to take place.     

Protective effect of methanol extract of Uncaria rhynchophylla against excitotoxicity induced by N-methyl-D-aspartate in rat hippocampus

Uncaria rhynchophylla is a medicinal herb used for convulsive disorders in Oriental medicine. In this study, the effect of the methanol extract of Uncaria rhynchophylla against N-methyl-D-aspartate (NMDA)-induced excitotoxicity was investigated. Pretreatment with the extract of Uncaria rhynchopylla reduced the degree of neuronal damage induced by NMDA exposure in cultured hippocampal slices. In the patch clamp study, Uncaria rhynchophylla significantly inhibited NMDA receptor-activated ion current in acutely dissociated hippocampal CA1 neurons. These results indicate that Uncaria rhynchophylla offers protection against NMDA-induced neuronal injury and inhibitory action on NMDA receptor-mediated ion current may be a mechanism behind the neuroprotective effect of Uncaria rhynchophylla.     

Inhibition of excitotoxicity in cultured rat cortical neurons by a mixture of conjugated linoleic acid isomers.

Glutamate excitotoxicity, which is mediated by both N-methyl-D-aspartate (NMDA) and non-NMDA receptors, directly contributes to the neuronal cell loss associated with both acute insults and chronic neurodegenerative disorders. Conjugated linoleic acid (CLA) is a group of dienoic derivatives of linoleic acid shown to have anticarcinogenic and antioxidative activities. To evaluate the effect of a mixture of CLA isomers (cis-9, trans-11 and cis-10, trans-12 octadecadienoic acids) on glutamate- and NMDA-induced excitotoxicity, primary cultures of rat cortical neurons were treated for 15 min with 300 microM glutamate or NMDA in the presence of various concentrations of CLA. After the exposure, cell cultures were maintained at 37 degrees C for 18 h in minimum essential medium supplemented with glucose. Neuronal injury was measured by a colorimetric cell proliferation assay, and a qualitative assessment was made by phase-contrast microscopy. CLA inhibited glutamate- and NMDA-induced neuronal cell death in a concentration-dependent fashion with the most effective dose for neuroprotection being 500 microM. These results demonstrate that a mixture of CLA isomers exhibits protective action against glutamate- and NMDA-induced excitotoxicity.     

Are neuronal nicotinic receptors a target for antiepileptic drug development? Studies in different seizure models in mice and rats

Altered function of neuronal nicotinic acetylcholine receptors in the brain has recently been associated with an idiopathic form of partial epilepsy, suggesting that functional alterations of these receptors can be involved in the processes leading to epileptic seizures. Thus, nicotinic acetylcholine receptors may form a novel target for antiepileptic drug development. In the present study, various nicotinic acetylcholine receptor antagonists, including novel amino-alkyl-cyclohexane derivatives, were evaluated in two animal models, namely the maximal electroshock seizure test in mice and amygdala-kindling in rats. For comparison with these standard models of generalized and partial seizures, the effects against nicotine-induced seizures were examined. Because some of the agents tested showed an overlap between channel blocking at nicotinic acetylcholine receptors and NMDA receptors, the potency at these receptors was assessed by using patch clamp in a hippocampal cell preparation. Preferential nicotinic acetylcholine receptor antagonists were potent anticonvulsants in the maximal electroshock seizure test and against nicotine-induced seizures. The anticonvulsant potency in the maximal electroshock seizure test was decreased by administration of a subconvulsant dose of nicotine. Such a potency shift was also seen with selective NMDA receptor antagonists, which were also efficacious anticonvulsants against both maximal electroshock seizures and nicotine-induced seizures. Experiments with agents combining nicotinic acetylcholine receptor and NMDA receptor antagonistic effects suggested that both mechanisms contributed to the anticonvulsant effect of the respective agents in the maximal electroshock seizure test. This was not found in kindled rats, in which nicotinic acetylcholine receptor antagonists exerted less robust effects. In conclusion, it may be suggested that nicotinic acetylcholine receptor antagonism might be a valuable therapeutic approach to treat generalized epileptic seizures but rather not complex partial seizures.     

Perspectives for the use of excitatory amino acid ionotropic receptor antagonists as antiepileptic drugs

Numerous antagonists of glutamate, belonging to N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists, were demonstrated to display anticonvulsant activity in various models of experimental epilepsy. Also, the glutamate antagonists enhanced the protective activity of conventional antiepileptic drugs against maximal electroshock-induced seizures in mice. However, some combinations of conventional antiepileptics with NMDA receptor antagonists resulted in profound adverse effects. In contrast, the antagonists for the non-NMDA receptor group potentiated the anticonvulsant activity of conventional antiepileptics, with no side-effects being observed. In some cases, the combined treatments were superior to the administration of an antiepileptic drugs alone, as regards adverse effects. In no case, glutamate antagonists affected the plasma levels of antiepileptic drugs. These data seem to indicate that non-NMDA receptor antagonists bear more important clinical potential as adjuvant antiepileptic drugs.     

Imidazoline-induced neuroprotective effects result from blockade of NMDA receptor channels in neuronal cultures

Imidazolines have been shown to be neuroprotective in focal and global ischemia in the rat. However, their mechanism of action is still unclear. We have studied the neuroprotective effects of imidazolines against NMDA-induced neuronal death and hypoxic insult in cerebellar and striatal neuronal cultures. All of the imidazolines tested decreased the NMDA-mediated neurotoxicity in a non-competitive manner. Antazoline was the most effective (IC(50) of 5 microM, maximal neuroprotection reaching 90% at 100 microM). The neuroprotective effects were still present when the imidazolines were applied during the post-insult period. Antazoline, idazoxan and guanabenz also showed neuroprotective effects against hypoxia-induced neuronal death (neuroprotection reaching 95% for antazoline at 100 microM). Antazoline was still active if applied during the reoxygenation period (15% neuroprotection). To determine the mechanism of the neuroprotective effects, the possible interaction of imidazolines with NMDA receptors was studied. Imidazolines dose-dependently and non-competitively inhibited NMDA currents. As found for the neuroprotective effects, antazoline was the most effective imidazoline, with an IC(50) of 4 microM and a maximal inhibition of 90% at 100 microM. This blockade was rapid, reversible and voltage-dependent. We compared these effects to those of the classical non-competitive antagonist of NMDA channels, MK-801. In contrast to imidazolines, blockade of the NMDA current by MK-801 was voltage-independent and reversible only at positive potentials. When co-applied with MK-801, antazoline prevented the long lasting blockade of the NMDA current by MK-801. These results are consistent with the existence of overlapping binding sites for these drugs on the NMDA receptor channel. They indicate that imidazolines exert a strong neuroprotective effect against excitotoxicity and hypoxia in cerebellar and striatal primary neuronal cultures by inhibiting NMDA receptors. Since these effects were non-competitive, imidazolines appear to be interesting new drugs with therapeutic potential.     

Neuroprotective effect of Smilacis chinae rhizome on NMDA-induced neurotoxicity in vitro and focal cerebral ischemia in vivo

Previous work has shown that the Smilacis chinae rhizome (SCR) markedly inhibits amyloid beta protein (25-35)-induced neuronal cell damage in cultured rat cortical neurons. The present study was conducted to further verify the neuroprotective effect of SCR on excitotoxic and cerebral ischemic injury using both in vitro and in vivo studies. Exposure of cultured cortical neurons to 1 mM N-methyl-D-aspartate (NMDA) for 12 h induced neuronal cell death. SCR (10 and 50 microg/ml) inhibited NMDA-induced neuronal death, elevation of intracellular calcium ([Ca(2+)](i)), and generation of reactive oxygen species (ROS) in primary cultures of rat cortical neurons. In vivo, SCR prevented cerebral ischemic injury induced by 3-h middle cerebral artery occlusion (MCAO) and 24-h reperfusion. The ischemic infarct was significantly reduced in rats that received SCR (30 and 50 mg/kg, orally), with a corresponding improvement in neurological function. Moreover, SCR treatment significantly decreased the histological changes observed following ischemia. Oxyresveratrol and resveratrol isolated from SCR also inhibited NMDA-induced neuronal death, increase in [Ca(2+)](i), and ROS generation in cultured cortical neurons, suggesting that the neuroprotective effect of SCR may be attributable to these compounds. Taken together, these results suggest that the neuroprotective effect of SCR against focal cerebral ischemic injury is due to its anti-excitotoxic effects and that SCR may have a therapeutic role in neurodegenerative diseases such as stroke.     

Neuroprotective effects of estrone on NMDA-induced toxicity in primary cultures of rat cortical neurons are independent of estrogen receptors

It has been hypothesized that some estrogenic metabolites with low hormonal activity, such as estrone or estriol, may serve as endogenous neuroprotective agents. Since estrone naturally occurs in abundance in the human brain, we evaluated its effects on the NMDA-induced toxicity in primary cultures of the rat cortical neurons. The results showed that NMDA (1 mM) had toxic effect on the rat cortical neurons on 12, but not on 7 day in vitro. This effect was partially prevented by DL-2-amino-5-phosphonovaleric acid (AP-5); a competetive NMDA receptor antagonist. Estrone (500 nM) attenuated the NMDA-induced toxicity in estrogen receptor-independent way. These data support the hypothesis that toxic effects of NMDA depend on stage of neuronal development and point to non-genomic neuroprotective actions of estradiol metabolites.