Generation and propagation of 4-AP-induced epileptiform activity in neonatal intact limbic structures in vitro

We examined the generation, propagation and pharmacology of 4-aminopyridine (4-AP)-induced epileptiform activity (EA) in the intact interconnected limbic structure of the newborn (P0-7) rat in vitro. Whole-cell recordings of CA3 pyramidal cells and multisite field potential recordings in CA3, CA1, dentate gyrus, and lateral and medial entorhinal cortex revealed 4-AP-induced EA as early as P0-1. At this age, EA was initiated in the CA3 region and propagated to CA1, but not to the entorhinal cortex. Starting from P3-4, EA propagated from CA3 to the entorhinal cortex. Along the CA3 septo-temporal axis, EA arose predominantly from the septal pole and spread towards the temporal site. Whereas the onset of 4-AP-induced EA decreased with age from 21.2 +/- 1.6 min at P0-1 to 4.7 +/- 0.63 min at P6-7, the seizure duration increased in the same age groups from 98 +/- 14 s to 269.4 +/- 85.9 s, respectively. The EA was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) but not by DL-2-amino-5-phosphonovaleric acid (APV), (+)-MK-801 hydrogen maleate (MK-801) or (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG), suggesting that they were mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptor activation. We conclude that: (i) the septal pole of the hippocampal CA3 region plays a central role in the generation of EA in the neonatal limbic system; and (ii) AMPA/kainate receptor-mediated EA can be generated in CA3 already at birth. Therefore, the recurrent collateral synapses and circuits required for the generation of EA are developed earlier than previously suggested on the basis of studies on hippocampal slices.     

红藻氨酸诱导癫痫发作大鼠海马结构中EAAC-1变化

目的 研究谷氨酸转运蛋白亚型（ＥＡＡＣ－１）在红藻氨酸（ＫＡ）诱导癫痫发作大鼠海马结构中的变化。方法 用红藻氨酸诱导的复杂部分性癫痫模型,将２０只ＳＤ大鼠随机分为３,６,１２,４８ｈ及对照５组,用免疫蛋白印记法（Ｗｅｓｔｅｒｎ ｂｌｏｔ）观察ＥＡＡＣ－１在海马结构上的变化。结果 ＫＡ注射后３ｈ海马ＥＡＡＣ－１开始减少,６ｈ显著减少,１２ｈ后ＥＡＡＣ－１逐渐恢复。结论 ＥＡＡＣ－１表达的调控可能与Ｋ     

Role of the forebrain in bladder overactivity following cerebral infarction in the rat

This study was undertaken to investigate the contribution of the forebrain to bladder overactivity induced by cerebral infarction (CI). CI was induced by left middle cerebral artery (MCA) occlusion in female SD rat. Two and a half hours after CI or a sham operation (SO) decerebration was performed in some animals to eliminate forebrain influences on voiding function. Then bladder activity was monitored during continuous infusion cystometrograms in awake rats for 2.5 h. The effects of cumulative intravenous doses of MK-801 (0.1-1.4 mg/kg), an NMDA (N-methyl-D-aspartate) glutamatergic receptor antagonist, or sulpiride (0.1-41.1 mg/kg), D(2) selective dopaminergic receptor antagonists were studied over a 1.5-h period beginning 5 h after MCA occlusion. Bladder capacity was reduced by 57.5% after CI. In CI rats decerebration increased bladder capacity by 62.5% of predecerebration capacity. In SO rats bladder capacity was reduced by 25% after decerebration. MK-801 (0.4 and 1.4 mg/kg) increased bladder capacity in CI and CI-decerebrate rats, but did not change bladder capacity in SO-decerebrate rats. MK-801 decreased (60.7%) bladder capacity in SO-nondecerebrate rats. Sulpiride (11.1 and 41.1 mg/kg) significantly increased bladder capacity in CI, CI-decerebrate, and SO-decerebrate rats, but had no effect in SO-nondecerebrate rats. These results indicate that CI-induced decrease in bladder capacity is mediated by two mechanisms: (1) upregulation of an excitatory pathway from the forebrain, an effect blocked by decerebration and (2) downregulation of a tonic inhibitory pathway from the forebrain. The latter effect which can be induced by decerebration as well as CI unmasks a D(2) dopaminergic excitatory mechanism. An NMDA excitatory mechanism also contributes to the bladder overactivity after CI, but not after decerebration.     

General anesthetics selectively modulate glutamatergic and dopaminergic signaling via site-specific phosphorylation in vivo

Isoflurane, propofol and ketamine are representative general anesthetics with distinct molecular mechanisms of action that have neuroprotective properties in models of excitotoxic ischemic damage. We characterized the effects of these agents on neuronal glutamate and dopamine signaling by profiling drug-induced changes in brain intracellular protein phosphorylation in vivo to test the hypothesis that they affect common downstream effectors. Anesthetic-treated and control mice were killed instantly by focused microwave irradiation, frontal cortex and striatum were removed, and the phosphorylation profile of specific neuronal signaling proteins was analyzed by immunoblotting with a panel of phospho-specific antibodies. At anesthetic doses that produced loss of righting reflex, isoflurane, propofol, and ketamine all reduced phosphorylation of the activating residue T183 of ERK2 (but not of ERK1); S897 of the NR1 NMDA receptor subunit; and S831 (but not S845) of the GluR1 AMPA receptor subunit in cerebral cortex. At sub-anesthetic doses, these drugs only reduced phosphorylation of ERK2. Isoflurane and ketamine also reduced phosphorylation of spinophilin at S94, but oppositely regulated phosphorylation of presynaptic (tyrosine hydroxylase) and postsynaptic (DARPP-32) markers of dopaminergic neurotransmission in striatum. These data reveal both shared and agent-specific actions of CNS depressant drugs on critical intracellular protein phosphorylation signaling pathways that integrate multiple second messenger systems. Reduced phosphorylation of ionotropic glutamate receptors by all three anesthetics indicates depression of normal glutamatergic synaptic transmission and reduced potential excitotoxicity. This novel approach indicates a role for phosphorylation-mediated down-regulation of glutamatergic synaptic transmission by general anesthetics and identifies specific in vivo targets for focused evaluation of anesthetic mechanisms.     

Astrocytes in the damaged brain: Molecular and cellular insights into their reactive response and healing potential

Long considered merely a trophic and mechanical support to neurons, astrocytes have progressively taken the center stage as their ability to react to acute and chronic neurodegenerative situations became increasingly clear. Reactive astrogliosis starts when trigger molecules produced at the injury site drive astrocytes to leave their quiescent state and become activated. Distinctive morphological and biochemical features characterize this process (cell hypertrophy, upregulation of intermediate filaments, and increased cell proliferation). Moreover, reactive astrocytes migrate towards the injured area to constitute the glial scar, and release factors mediating the tissue inflammatory response and remodeling after lesion. A novel view of astrogliosis derives from the finding that subsets of reactive astrocytes can recapitulate stem cell/progenitor features after damage, fostering the concept of astroglia as a promising target for reparative therapies. But which biochemical/signaling pathways modulate astrogliosis with respect to both the time after injury and the type of damage? Are reactive astrocytes overall beneficial or detrimental for neuroprotection and tissue regeneration? This debate has been animating this research field for several years now, and an integrated view on the results obtained and the possible future perspectives is needed. With this Commentary article we have attempted to answer the above-mentioned questions by reviewing the current knowledge on the molecular mechanisms controlling and sustaining the reaction of astroglia to injury and its stem cell-like properties. Moreover, the cellular/molecular mechanisms supporting the detrimental or beneficial features of astrogliosis have been scrutinized to gain insights on possible pharmacological approaches to enhance astrocyte neuroprotective activities.     

N-甲基-D-天门冬氨酸受体亚型NR1、NR2A在大鼠视网膜缺血再灌注损伤模型中的表达

目的:研究N-甲基-D-天门冬氨酸受体(N-methyl-D-aspartate receptor,NMDAR)功能亚单位NMDAR1、NM-DAR2A在Wister大鼠视网膜缺血再灌注模型中的表达情况。方法:18只健康成年Wister大鼠分成6组,每组3只,都取其右眼行视神经周围血管结扎手术制备视网膜缺血再灌注模型,左眼作为对照组不行手术。60分钟后去除结扎缝线恢复血流,分别于再灌注后即刻、3、12、24、72、168小时处死大鼠,摘除眼球,做冰冻切片。用免疫组织化学方法观察NR1、NR2A在视网膜缺血再灌注后不同时刻的变化并进行图象分析及统计学处理。结果:(1)各实验组和对照组间及各实验组间NMDAR1的表达无统计学意义。(2)除即刻组外各实验组和对照组间及各实验组间NMDAR2A的表达均有统计学意义,从再灌注后3小时至168小时NMDR2A表达缓慢上升。结论:(1)NMDAR1与视网膜缺血再灌注损伤无关,不参与谷氨酸的兴奋性毒性作用。(2)NMDAR2A与视网膜缺血再灌注损伤有关,参与谷氨酸兴奋性毒性作用。     

碱性成纤维细胞生长因子对谷氨酸毒性损伤豚鼠视网膜内突触小泡蛋白表达的影响

目的:探讨过量谷氨酸毒性损伤豚鼠视网膜内突触小泡蛋白(SYP)的表达及碱性成纤维细胞生长因子(bFGF)对其表达的影响。方法:豚鼠随机分成谷氨酸钠损伤组、对照组和bFGF治疗组。采用免疫组织化学方法和图像分析技术,对各组豚鼠视网膜内SYP免疫反应产物的表达进行检测。结果:对照组豚鼠视网膜内SYP的表达为强阳性,主要定位于外网状层和内网状层,损伤组视网膜相应区域内阳性反应产物的光密度值明显低于对照组,bFGF治疗后SYP的阳性表达明显高于损伤组,且与对照组相比,无显著性差异。结论:bFGF可抑制过量谷氨酸钠诱发的视网膜内SYP的表达减少,上调SYP的表达,对视神经损伤有显著地促功能修复作用。     

补阳还五汤对全脑缺血再灌注不同时点大鼠皮质神经细胞谷氨酸受体2表达的影响

目的 研究补阳还五汤抗全脑缺血后再灌注损伤的分子机制.方法 将SD大鼠随机分为3组,即正常组、模型组和药物组(补阳还五汤预干预),模型组和药物组再分别设置2、12、24、48、72 h五个观察时间点.连续给药5 d后,采用改良的Pulsinelli四血管闭塞法复制全脑缺血大鼠模型,再灌注后2、12、24、48、72 h分别检测各组大鼠皮质神经细胞谷氨酸受体2(glutamate receptor 2,GluR2)的表达水平.结果 与正常组比较,再灌注各时点模型组大鼠大脑皮质神经细胞GluR2表达水平显著降低(P<0.01);与模型组比较,再灌注各时点药物组GluR2表达水平显著升高(P<0.01);与再灌注2 h比较,再灌注12、24、48、72 h药物组GluR2表达水平显著升高(P<0.01).结论 补阳还五汤可预防大鼠脑缺血再灌注引起的GluR2表达减少,且在再灌注2 h后这种抑制作用更强.     

Neuroprotective action of lithium in disorders of the central nervous system

Substantial in vitro and in vivo evidence of neurotrophic and neuroprotective effects of lithium suggests that it may also have considerable potential for the treatment of neurodegenerative conditions.Lithium's main mechanisms of action appear to stem from its ability to inhibit glycogen synthase kinase-3 activity and also to induce signaling mediated by brain-derived neurotrophic factor.This in turn alters a wide variety of downstream effectors,with the ultimate effect of enhancing pathways to cell surviva...     

Visual Performance in Monosodium Glutamate-Treated Rats

Abstract

The purpose of this study was to examine the effect of monosodium glutamate on the visual performance in rats. The Wistar strain of neonatal rats were injected subcutaneously with a solution of the glutamate at doses of 1 or 2 or 4 mg/gm body weight on days 2, 4, 6, 8 and 10 postnatally. Control rats received an injection of physiological saline. At 1, 2 and 3 months of age, the rats were tested for visual performance (brightness discrimination, pattern discrimination and visual acuity). As a result, the 4 mg/gm glutamate treatment was observed to impair brightness discrimination performance at 1 month of age as compared to the control animals. This impairment was also observed in animals at 2 and 3 months as compared, in addition, to the values in other doses of glutamate treatment. Pattern discrimination performance in every group of animals was at the same level at 1 month of age. However, at 2 months of age, the performance in the 2- and 4 mg/gm glutamate-treated groups was lower than those in the control group. This comparison was more pronounced at 3 months of age. Visual acuity performance results were quite the same as the pattern discrimination performance at all ages of animals. In conclusion, glutamate treatment was shown to cause dose-dependent deficit in visual performance and this may reflect impairment of visual organs and brain function.