甲基苯丙胺急性处理对大鼠纹状体中神经元和谷氨酸转运体的影响

目的:观察甲基苯丙胺(METH)急性处理致神经损伤情况,以及纹状体中谷氨酸转运体1(GLT1)与囊泡型谷氨酸转运体1(VGLUT1)的变化。方法:建立METH急性毒性模型,同时利用谷氨酸转运体激动剂头孢曲松调控谷氨酸转运体的表达,尼氏染色实验观测神经元中尼氏小体的变化,利用Western blot实验检测其谷氨酸转运体蛋白表达的变化。结果:与盐水对照组相比,METH给药组刻板行为明显增加(P<0.01),尼氏小体显著减少,纹状体中GLT1和VGLUT1的表达增加分别为23.1%和66.1%(P<0.05);与METH组相比,头孢曲松预防给药组大鼠刻板行为明显减少,纹状体中GLT1的表达增加15.2%(P<0.05),VGLUT1的表达降低,但没有统计学意义(P>0.05)。结论:METH急性处理能导致神经损伤,引起纹状体中谷氨酸转运体的表达变化;头孢曲松能激活谷氨酸转运体的表达,缓解METH引起的神经损伤。     

头孢曲松对甲基苯丙胺致大鼠行为及纹状体氨基酸等递质含量改变的影响

目的观察甲基苯丙胺(METH)急性处理时致神经损伤情况,以及纹状体中氨基酸类神经递质谷氨酸(glutamate,Glu)、单胺类神经递质多巴胺(dopamine,DA)及其代谢产物DOPAC的变化。方法建立METH急性毒性模型,同时利用药物头孢曲松进行干预,利用清醒动物脑微透析技术检测神经递质含量的变化。结果 METH急性给药组与盐水对照组相比,刻板行为明显增加(P<0.01);急性给予METH后,胞外Glu浓度持续增加,在本试验检测时间(0～6 h)范围内,与基础平衡值相比,在给药5.5 h时Glu浓度已增加450%。胞外DA水平在1 h达峰值,与基础平衡值相比,浓度增加1248.6%。与METH组相比,头孢曲松预防给药可明显降低大鼠纹状体胞外Glu浓度(P<0.05)。结论 METH急性处理能引起纹状体中胞外谷氨酸的含量明显增加,导致神经损伤;METH的神经毒性与兴奋性氨基酸的过度释放密切相关。     

甲基苯丙胺对斑马鱼行为模式及相关基因表达变化的影响

目的利用斑马鱼这一新型模式动物建立行为模型,考察成瘾性药物甲基苯丙胺对于斑马鱼游泳行为的影响及谷氨酸转运体表达量的变化。方法利用斑马鱼行为视频跟踪分析系统自动记录动物行为参数,运动路程、穿越次数及在顶部停留时间作为测试指标,采用甲基苯丙胺5 mg·L-1,20 mg·L-1和50 mg·L-1,分别考察急性暴露及作用24 h后对于斑马鱼行为影响,之后利用实量定量PCR考察质膜型谷氨酸转运体(GLT1)和囊泡型谷氨酸转运体(VGLUT)表达量变化。结果急性暴露条件下,与正常组相比,斑马鱼垂直方向的穿越次数及在上半区停留时间呈非常显著的下降(P<0.01),且这种降低与甲基苯丙胺浓度有剂量依赖关系。在甲基苯丙胺急性处理后24 h,斑马鱼垂直方向的穿越次数及在上半区停留时间仍呈显著的下降(P<0.01)但不具有剂量依赖关系。急性暴露后斑马鱼脑GLT1显著下调(P<0.05),VGLUT3显著上调(P<0.01)。24 h后GLT1的表达量有所上调,VGLUT3上调趋势更加显著(P<0.01),但均无剂量关系。结论建立了甲基苯丙胺致斑马鱼神经损伤模型,甲基苯丙胺对于斑马鱼行为产生特征性影响且具有剂量关系。     

头孢曲松神经保护作用及其与胶质细胞谷氨酸转运体1表达的关系

目的:研究头孢曲松对神经细胞的保护作用及其机制。方法:培养大鼠脑皮层神经细胞,加头孢曲松保护和谷氨酸损伤,光镜及四氮唑蓝(MTT)比色法观察细胞改变,逆转录-聚合酶链反应(RT- PCR)检测GLT1 mRNA、EAAC1 mRNA表达变化;激光共聚焦显微镜(LSCM)实时观测加或不加二氢红藻氨酸(DHK)后谷氨酸诱导钙超载时细胞内Ca~(2+)荧光强度变化。结果:头孢曲松组较对照组神经细胞损伤减轻,GLT1 mRNA表达增加(0.435±s 0.006,P<0.01);细胞内Ca~(2+)荧光强度在钙超载后上升缓慢但恢复迅速,加入DHK后,与对照组变化基本相同。结论:头孢曲松通过上调GLT1 mRNA表达,减轻谷氨酸细胞毒性和内钙超载,对神经细胞产生保护作用。     

甲基苯丙胺所致的大鼠神经毒性损伤及nNOS抑制剂的保护作用

目的探讨神经元型一氧化氮合酶(nNOS)在甲基苯丙胺(METH)所致大鼠中枢神经系统氧化应激损伤中的作用机制。方法建立METH中毒动物模型,并给予nNOS抑制剂7硝基吲唑(7-NI)预处理,观察各组间动物行为学的变化,并检测nNOS表达、多巴胺(DA)含量、硝基化蛋白表达及凋亡等指标。结果 METH组大鼠纹状体中nNOS蛋白表达水平明显升高,而METH+7-NI组nNOS表达水平较METH组明显降低。METH组DA明显降低(P<0.01),而METH+7-NI组、7-NI组与对照组比较,DA无差异(P>0.05)。METH组硝基化蛋白含量明显升高(P<0.01),而METH+7-NI组硝基化蛋白表达较METH组明显降低(P<0.05)。METH组与对照组相比,凋亡细胞数明显升高(P<0.01),而7-NI对凋亡的增高表现出明显的保护作用(与METH组相比P<0.01)。METH组和METH+7-NI组的动物刻板行为评分均明显高于7-NI和对照组(P<0.01),METH、METH+7-NI组间差异无显著性(P>0.05)。结论METH可导致大鼠大脑纹状体nNOS蛋白表达水平增高、DA含量的降低、硝基化蛋白水平升高及细胞凋亡增多等多种神经毒性表现,7-NI能部分减轻其神经毒性作用。METH明显增加大鼠的不自主刻板运动,而应用7-NI预处理后,对刻板行为的改善并不明显。     

甲基苯丙胺对SH-SY5Y细胞的毒性作用及对α-核突触蛋白表达的影响

目的:探讨甲基苯丙胺(methamphetamine,METH)对SH-SY5Y细胞的毒性作用和对α-核突触蛋白(α-synuclein,α-SN)表达的影响,为研究α-SN在METH神经毒性机制中的作用奠定基础。方法:分别用浓度0、0.5、1.5、2.5、3.5、4.5 mmol.L-1的METH处理SH-SY5Y细胞24 h,倒置显微镜下观察细胞形态变化;透射电镜观察细胞超微结构;CCK-8法检测细胞存活率;流式细胞术分析细胞凋亡率;实时荧光定量PCR和Western Blot分别检测α-SN基因和蛋白水平的表达变化。结果:以0 mmol.L-1为对照组,0.5-4.5 mmol.L-1METH处理的SH-SY5Y细胞镜下可见胞体皱缩变圆,突起变短、断裂、消失。电镜显示,METH处理的细胞内可见包涵体和自噬小体。0.5 mmol.L-1处理组与对照组比较,细胞存活率无显著性差异(P=0.274),其他浓度处理组与对照组相比均有显著性差异(P<0.001)。细胞凋亡率随METH浓度增加而递增,与对照组相比均有显著性差异(P<0.001)。与对照组比较,0.5 mmol.L-1处理组α-SN-mRNA的表达量没有显著差异(P=0.936),其他浓度处理组α-SN-mRNA均显著性上升(P<0.001),且α-SN-mRNA表达量随METH浓度增加而逐步上升。α-SN蛋白的表达也随METH浓度增加而递增。结论:METH对SH-SY5Y细胞有毒性作用并可刺激细胞中α-SN基因和蛋白水平的高表达。细胞毒性作用和α-SN的表达均随METH浓度的增加而递增。     

谷氨酸受体1与钩藤碱抑制甲基苯丙胺依赖斑马鱼条件性位置偏爱的关系

目的研究钩藤碱对甲基苯丙胺(METH)依赖斑马鱼产生条件性位置偏爱(CPP)的影响,以及谷氨酸受体1(GluR1)对METH依赖斑马鱼的作用机制。方法斑马鱼随机分为5组:对照组、模型组、钩藤碱低剂量组(50 mg·kg~(-1))、钩藤碱高剂量组(100 mg·kg~(-1))和氯胺酮组(150 mg·kg~(-1))。斑马鱼腹腔注射METH后,进行CPP训练,建立斑马鱼METH依赖CPP模型,分析各组斑马鱼在CPP箱中的活动,采用免疫组化和Western blot等方法研究各组斑马鱼脑内GluR1的表达情况。结果腹腔注射METH 40 mg·kg~(-1)后,METH依赖斑马鱼CPP模型成功建立。与对照组相比,模型组斑马鱼在白箱中的停留时间明显增加;与模型组相比,钩藤碱高剂量组斑马鱼在白箱中的停留时间明显减少。与对照组相比,模型组斑马鱼脑内GluR1阳性细胞数及GluR1蛋白的表达明显增加;钩藤碱干预后,斑马鱼脑内GluR1阳性细胞数明显减少。结论钩藤碱在一定程度上可以抑制METH诱导斑马鱼产生CPP效应,其作用机制可能与斑马鱼脑内GluR1的表达有关。     

甲基苯丙胺对体外培养SH-SY5Y细胞线粒体膜电位、超微结构及Mfn1、Fis1蛋白表达的影响

目的评估甲基苯丙胺(METH)对体外培养的SHSY5Y细胞线粒体膜电位(MMP)、线粒体超微结构及Mfn1、Fis1蛋白表达的影响。方法 SH-SY5Y细胞中加入METH(0. 0、1. 0、1. 5、2. 0 mmol·L~(-1)),培养3、6、12、24 h; JC~(-1)法检测SH-SY5Y细胞MMP;透射电镜观察SH-SY5Y细胞线粒体超微结构; Western blot检测Mfn1、Fis1蛋白表达。结果METH作用SH-SY5Y细胞3、6、12、24 h,与对照组比较,METH组细胞MMP红绿荧光比值明显降低(P <0. 05),Mfn1蛋白表达降低(P <0. 05),Fis1蛋白表达升高(P <0. 05); METH作用SH-SY5Y细胞24 h时,透射电镜观察见未处理组细胞线粒体呈椭圆形棒状双层膜结构,线粒体嵴正常、清晰,METH组细胞线粒体椭圆形棒状结构被分裂成小球状结构,并发现线粒体自噬小体及自噬溶酶体。结论METH可引起SH-SY5Y细胞MMP下降、线粒体超微结构改变及Mfn1、Fis1蛋白表达水平改变,其改变可能参与METH致神经细胞损伤的发病机制。     

Iptkalim inhibits cocaine challenge—induced enhancement of dopamine levels in nucleus accumbens and striatum of rats by up—regulating Kir6.1 and Kir6.2 mRNA expression

目的:研究钾通道开放剂埃他卡林对急慢性可卡因应用引起的伏隔核、纹状体和额叶皮层的多巴胺和谷氨酸水平变化的影响及其机制。方法:采用高效液相色谱与电化学检测、荧光检测联用的方法测定各脑区谷氨酸和多巴胺的含量;采用半定量逆转录聚合酶链反应(RT-PCR)研究ATP敏感性钾通道亚单位Kir6.1、Kir6.2、SUR1和SUR2 mRNA表达的变化。结果:埃他卡林不影响急性可卡因应用引起纹状体和伏隔核中多巴胺和谷氨酸水平的增高(P>0.05),能够逆转激发剂量可卡因诱导的慢性成瘾大鼠纹状体和伏隔核的多巴胺含量增高(P<0.05),对激发后皮层和伏隔核谷氨酸水平增高有降低趋势但差异无显著性(P>0.05)。激发剂量可卡因能提高可卡因预处理组和埃他卡林预处理组纹状体和伏隔核的Kir6.1和Kir6.2 mRNA表达以及皮层的Kir6.2 mRNA表达,而且IPT预处理组的升高幅度显著高显著高于可卡因慢性处 理组。结论:埃他卡林通过上调Kir6.1和Kir6.2 mRNA表达抑制可卡因激发引起的纹状体和伏隔核的多巴胺水平的增高。     

木犀草素对脊髓损伤大鼠Nrf2/HO-1通路的影响

摘要：目的:观察木犀草素对脊髓损伤大鼠的影响,并初步探讨其作用机制。方法:将SD大鼠随机分为假手术组、模型组、木犀草素低、中、高剂量组和阳性对照组,除假手术组外,其余各组均采用改良的Allen重物打击法制备大鼠脊髓损伤（SCI）模型,建模成功后,分别给予生理盐水、10 mg·kg-1木犀草素、20 mg·kg-1木犀草素、40 mg·kg-1木犀草素、30 mg·kg-1甲泼尼龙2 ml灌胃处理,q12 h,连续7d。采用BBB评分法检测大鼠下肢运动功能恢复情况;苏木素-伊红（HE）染色观察脊髓损伤区神经元形态变化情况;末端脱氧核苷酸转移酶介导的缺口末端标记（TUNEL）测定大鼠脊髓损伤组织细胞凋亡情况;酶联免疫吸附（ELISA）法检测脊髓损伤组织中丙二醛（MDA）水平和超氧化物歧化酶（SOD）活性;蛋白免疫印迹分析法检测核转录因子红系2相关因子2（Nrf2）、血红素加氧酶-1（HO-1）蛋白表达。结果:假手术组尼氏小体多且均匀分布,神经元结构清晰;模型组神经元胞体固缩,形态各异,尼氏小体数量明显减少;木犀草素各剂量组及阳性对照组尼氏小体数量增多,神经元损伤较模型组有所好转。与假手术组相比,模型组TUNEL阳性细胞数、MDA浓度、Nrf2和HO-1蛋白表达水平显著升高（P<0.05）,BBB评分、SOD活性显著降低（P<0.05）;与模型组相比,木犀草素低、中、高剂量组TUNEL阳性细胞数、MDA浓度呈剂量依赖性降低（P<0.05）,BBB评分、Nrf2、HO-1蛋白表达水平和SOD活性呈剂量依赖性升高（P<0.05）;与木犀草素低、中剂量组相比,阳性对照组术后3 d和术后7 d的BBB评分、SOD活性、Nrf2和HO-1蛋白表达水平升高,TUNEL阳性细胞数、MDA浓度降低（P<0.05）;与木犀草素高剂量组相比,阳性对照组术后3 d的BBB评分、Nrf2蛋白表达水平降低,术后7 d的BBB评分、HO-1蛋白表达水平升高（P<0.05）。结论:木犀草素能够改善大鼠脊髓损伤,可能与促进大鼠脊髓组织Nrf2/HO-1通路活化,降低氧化应激相关。     

Effects of ceftriaxone on ethanol intake: a possible role for xCT and GLT-1 isoforms modulation of glutamate levels in P rats

Rationale

Evidence suggests that glutamate transporter 1 (GLT-1) and cystine/glutamate exchanger transporter (xCT) are critical in maintaining glutamate homeostasis. We have recently demonstrated that ceftriaxone treatment induced upregulation of GLT1 levels and attenuated ethanol intake; however, less is known about the involvement of xCT on ethanol intake. In this study, we investigated the effects of ceftriaxone on the levels of xCT in both continuous and relapse-like ethanol drinking, as well as GLT-1 isoforms, and glutamate aspartate transporter (GLAST) in relapse-like ethanol intake.

Methods

P rats received free choice of 15 and 30 % ethanol and water for 5 weeks and then deprived of ethanol for 2 weeks. Rats were treated with ceftriaxone (100 mg/kg, i.p.) or saline during the last 5 days of the 2-week deprivation period. After deprivation period, P rats were re-exposed to free choice of 15 and 30 % ethanol and water for nine consecutive days. A second group of P rats was given continuous ethanol access for 5 weeks, then ceftriaxone (100 mg/kg, i.p.) or saline throughout the week 6.

Results

Ceftriaxone significantly attenuated relapse-like ethanol intake. Importantly, this effect of ceftriaxone was associated in part with upregulation of the levels of GLT-1a and GLT-1b isoforms and xCT in the prefrontal cortex (PFC) and the nucleus accumbens (NAc). There were no significant differences in GLAST expression among all groups. We also found that ceftriaxone treatment increased xCT levels in both PFC and NAc in continuous ethanol intake.

Conclusion

These findings suggest that xCT and GLT-1 isoforms might be target proteins for the treatment of alcohol dependence.     

Developmentally regulated expression of VGLUT3 during early post-natal life

Three subtypes of vesicular glutamate transporters, named VGLUT1-3, accumulate glutamate into synaptic vesicles. In this study, the post-natal expression of VGLUT3 was determined with specific probes and antiserums in the rat brain and compared with that of VGLUT1 and VGLUT2. The expression of VGLUT1 and VGLUT2 increases linearly during post-natal development. In contrast, VGLUT3 developmental pattern appears to have a more or less biphasic profile. A first peak of expression is centered around post-natal day 10 (P10) while the second one is reached in the adult brain. Between P1 and P15, VGLUT3 is observed in the frontal brain (striatum, accumbens, and hippocampus) and in the caudal brain (colliculi, pons and cerebellum). During a second phase extending from P15 to adulthood, the labeling of the caudal brain fades away. The adult pattern is reached at P21. We further analyzed the transient expression of VGLUT3 in the cerebellum and found it to correspond to a temporary expression in Purkinje cells. At P10 VGLUT3 immunoreactivity was present both in the soma and terminals of Purkinje cells (PC), where it colocalized with the vesicular inhibitory amino acid transporter (VIAAT). In agreement with data from the literature [Gillespie, D.C., Kim, G., Kandler, K., 2005. Inhibitory synapses in the developing auditory system are glutamatergic. Nat. Neurosci. 8, 332-338], our results suggest that during the first 2 weeks of post-natal life PC may have the potential to transiently release simultaneously GABA and glutamate.     

Up‐regulated GLT‐1 Resists Glutamate Toxicity and Attenuates Glutamate‐induced Calcium Loading in Cultured Neurocytes

Glutamate transporter‐1 (GLT‐1) plays a dual role in glutamate transportation: both normally devotion to the clearance of glutamate and during some pathological conditions extruding glutamate to the extracellular space. Therefore, it is uncertain whether increased expression of GLT‐1 will actually be helpful against glutamate excitotoxicity. In this study, GLT‐1 up‐regulation was induced by ceftriaxone, and L‐glutamate was added to induce glutamate toxicity in primary cultured rat cortical cells. The results showed that up‐regulated GLT‐1 induced by 1 μM ceftriaxone for 2 days markedly increased cell viability, decreased apoptotic cell death and alleviated ultrastructural damage induced by 50 μM glutamate 15 min. as well as promoted L‐[³H]‐glutamate uptake in cultured cells. GLT‐1 up‐regulation had no effect on the intracellular free calcium concentration ([Ca²⁺]_i) in the resting situation, while relieved intracellular calcium overloading by reducing the elevation and promoting the recovery of [Ca²⁺]_i following stimulation of 50 μM glutamate for 2 min. Applying 100 μM dihydrokainic acid (GLT‐1 antagonist) 30 sec. before glutamate eliminated the above effect of GLT‐1 up‐regulation on [Ca²⁺]_i. In conclusion, GLT‐1 up‐regulation induced by ceftriaxone plays a positive glutamate transporting role against glutamate toxicity in primary cultured rat cortical cells.     

Prenatal exposure to the cannabinoid receptor agonist WIN 55,212-2 increases glutamate uptake through overexpression of GLT1 and EAAC1 glutamate transporter subtypes in rat frontal cerebral cortex

Prenatal exposure to the CB1 receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)-pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) mesylate (WIN) at a daily dose of 0.5 mg/kg, and Delta9-tetrahydrocannabinol (Delta9-THC) at a daily dose of 5 mg/kg, reduced dialysate glutamate levels in frontal cerebral cortex of adolescent offspring (40-day-old) with respect to those born from vehicle-treated mothers. WIN treatment induced a statistically significant enhancement of Vmaxl-[3H]glutamate uptake, whereas it did not modify glutamate Km, in frontal cerebral cortex synaptosomes of adolescent rats. Western blotting analysis, performed either in membrane proteins derived from homogenates and in proteins extracted from synaptosomes of frontal cerebral cortex, revealed that prenatal WIN exposure enhanced the expression of glutamate transporter 1 (GLT1) and excitatory amino acid carrier 1 (EAAC1). Moreover, immunocytochemical analyses of frontal cortex area revealed a more intense GLT1 and EAAC1 immunoreactivity (ir) distribution in the WIN-treated group. Collectively these results show that prenatal exposure to the cannabinoid CB1 receptor agonist WIN increases expression and functional activity of GLT1 and EAAC1 glutamate transporters (GluTs) associated to a decrease of cortical glutamate outflow, in adolescent rats. These findings may contribute to explain the mechanism underlying the cognitive impairment observed in the offspring of mothers who used marijuana during pregnancy.     

Identification of glutamate transporters and receptors in mouse testis

INTRODUCTION Glutamate is the predominant excitatory neu-rotransmitter in the central nervous system (CNS). Itsneurotransmission can be mediated by various ligand-gated ion channels, of which there are three subtypes.These subtypes, which are classified on the basis ofsequence homologies and agonist affinities, are N-methyl-D-aspartate (NMDA) receptors (NR1 andNR2A-D), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors (GluR1-4), and kainate(KA) receptors (GluR5-7…     

谷氨酸转运体亚型谷氨酸转运体1与其调控药物的研究进展

胞外谷氨酸浓度的动态平衡是由谷氨酸转运体精确调控的,谷氨酸转运体功能或表达失调时导致胞外谷氨酸水平异常,引起一系列神经系统疾病。其中谷氨酸转运体1(GLT-1)起着"谷氨酸泵"作用,近年来还发现了仅在肽链C末端发生改变的GLT-1剪切变异体;其中GLT-1a、GLT-1b和GLT-1v发现与某些疾病具有相关性。药物调控谷氨酸转运体的表达或功能,维持胞外谷氨酸正常浓度,能有效改善病理状况。目前已有多种药物被报道对谷氨酸转运体具有激动或抑制作用,如能够上调GLT-1活性的药物有头孢曲松、苯环己哌啶、胞二磷胆碱、利鲁唑、凝血酶、蛋白激酶B等;下调GLT-1活性的药物有依托咪酯、氯氮平、天冬酰胺类衍生物、内皮素等。该文将调控谷氨酸转运体的药物做一总结,为药物开发和临床治疗提供新的思路。     

The glutamate and neutral amino acid transporter family: physiological and pharmacological implications

The solute carrier family 1 (SLC1) is composed of five high affinity glutamate transporters, which exhibit the properties of the previously described system XAG-, as well as two Na+-dependent neutral amino acid transporters with characteristics of the so-called "ASC" (alanine, serine and cysteine). The SLC1 family members are structurally similar, with almost identical hydropathy profiles and predicted membrane topologies. The transporters have eight transmembrane domains and a structure reminiscent of a pore loop between the seventh and eighth domains [Neuron 21 (1998) 623]. However, each of these transporters exhibits distinct functional properties. Glutamate transporters mediate transport of L-Glu, L-Asp and D-Asp, accompanied by the cotransport of 3 Na+ and one 1 H+, and the countertransport of 1 K+, whereas ASC transporters mediate Na+-dependent exchange of small neutral amino acids such as Ala, Ser, Cys and Thr. Given the high concentrating capacity provided by the unique ion coupling pattern of glutamate transporters, they play crucial roles in protecting neurons against glutamate excitotoxicity in the central nervous system (CNS). The regulation and manipulation of their function is a critical issue in the pathogenesis and treatment of CNS disorders involving glutamate excitotoxicity. Loss of function of the glial glutamate transporter GLT1 (SLC1A2) has been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS), resulting in damage of adjacent motor neurons. The importance of glial glutamate transporters in protecting neurons from extracellular glutamate was further demonstrated in studies of the slc1A2 glutamate transporter knockout mouse. The findings suggest that therapeutic upregulation of GLT1 may be beneficial in a variety of pathological conditions. Selective inhibition of the neuronal glutamate transporter EAAC1 (SLC1A1) but not the glial glutamate transporters may be of therapeutic interest, allowing blockage of glutamate exit from neurons due to "reversed glutamate transport" of EAAC1, which will occur during pathological conditions, such as during ischemia after a stroke.     

Changes in the Neuronal Glutamate Transporter EAAT3 in Rat Brain after Exposure to Methamphetamine

Methamphetamine (METH), an addictive psychostimulant, can induce glutamate release in several brain areas such as cerebral cortex, hippocampus and striatum. Excess glutamate is ordinarily removed from the synaptic cleft by glutamate transporters for maintaining homoeostasis. EAAT3, a subtype of glutamate transporter expressed mainly by neurons, is a major glutamate transporter in the hippocampus and cortex. Therefore, this study examined the effects of acute and sub‐acute METH administration on the expression of the EAAT3 in the hippocampal formation, striatum and frontal cortex. Male Sprague–Dawley rats received vehicle injections (i.p.) for 13 days followed by one injection of METH (8 mg/kg, i.p.) on day 14 in acute group. Animals received METH (4 mg/kg, i.p.) or vehicle for 14 days in sub‐acute and control groups, respectively. EAAT3 immunoreactivity was determined by western blotting followed by measurement of the integrated optical density. A significant increase in EAAT3 was found in the hippocampal formation after sub‐acute, but not acute, METH administration. Conversely, a significant decrease in EAAT3 in striatum was observed in both acute and sub‐acute groups. A trend towards a decrease in EAAT3 was also found in frontal cortex in the sub‐acute group. Our results of decreased EAAT3 in striatum and frontal cortex suggest deficits of cortico‐striatal glutamatergic synapses after METH exposure. Increased EAAT3 expression in the hippocampus may be a compensatory response to possible deficits of glutamatergic neurotransmission induced by METH. Moreover, our findings provide further support for glutamatergic dysfunction with abnormalities involving a transporter important in the regulation of neuronal glutamate.