N-Methyl-D-Aspartate受体拮抗剂对脑缺血后成年大鼠神经干细胞内源性激活的实验研究

目的　研究N - Methyl- D- Aspartate(NMDA)受体拮抗剂MK- 80 1对脑缺血后神经干细胞(NSC)激活的作用。方法　将4 0只SD大鼠分成对照组和实验组,两组大鼠均采用传统线栓法作成大脑中动脉缺血再灌注模型,实验组大鼠腹腔注射MK- 80 1,对照组腹腔注射生理盐水,通过免疫组织化学技术标记鼠脑海马齿状回颗粒细胞层(SGZ)、室管膜下层(SVZ)及梗死皮质周边区注射后第3、7、11、18天的Brdu、Nestin阳性细胞数。结果　对照组大鼠Brdu、Nestin阳性细胞7d在SGZ出现一小高峰,然后迅速下降,11d阳性细胞甚少,梗死皮质周边区更少;而实验组Brdu、Nestin阳性细胞3d在SVZ明显表达,7～11d在SGZ区达高峰,并可持续至18d,同样梗死皮质区Brdu、Nestin阳性细胞7～18d表达明显,两组比较,有统计学意义(P<0 .0 1)。结论　NMDA受体拮抗剂MK- 80 1在脑缺血后,能促进NSC的增殖、分化。     

NMDA受体拮抗剂MK-801对新生大鼠室管膜下区胶质纤维酸性蛋白表达的影响

目的研究N-甲基-D-天冬氨酸(NMDA)受体拮抗剂MK-801对新生7 d大鼠室管膜下区(SVZ)胶质纤维酸性蛋白(GFAP)表达的影响。方法将40只新生SD大鼠分成对照组和MK-801组,各组按出生后(P)时间点再随机分成4个亚组:P7 d、P14 d、P21 d、P28 d组。新生大鼠均于生后第3天给药,MK-801组腹腔注射MK-801 10 mg.kg-1;对照组腹腔注射同量生理盐水。通过免疫组化学方法观察大鼠SVZ区GFAP阳性细胞数。结果①对照组GFAP阳性细胞数于P14 d开始增加,至P21 d达最大值;但P28 d时阳性细胞迅速下降;②MK-801组GFAP阳性细胞数与对照组相比,P7 d和P28 d无明显差异,P14 d(65.40±6.11)和P21 d(239.60±12.92)细胞数明显减少;而对照组P14 d(79.20±5.26)、P21 d(265.20±7.40)GFAP阳性细胞数明显增多,差异有显著统计学意义(P<0.01)。结论 NMDA受体拮抗剂MK-801对正常新生大鼠SVZ区GFAP的表达有抑制作用,能够抑制SVZ区神经干细胞的增殖和分化。     

雌激素对大鼠脑缺血再灌注神经干细胞内源性激活的实验研究

目的探讨雌激素对脑缺血再灌注神经干细胞(neural stem cell,NSC)内源性激活的作用.方法将44只雄性大鼠随机分成假手术组、对照组和实验组.采用传统的线栓法制备大鼠大脑中动脉闭塞再灌注模型,实验组大鼠腹腔注射苯甲酸雌二醇,对照组腹腔注射生理盐水,通过免疫组织化学技术标记大鼠海马齿状回颗粒下层(subgranular zone,SGZ)、侧脑室室下层(subventricular zone,SVZ)以及梗死皮质周边区在缺血再灌注3、7、11、18 d的5-溴脱氧尿嘧啶核苷(bromodeoxyuridine,BrdU)阳性细胞,并采用HPIAS图像分析系统进行分析.结果正常成年大鼠脑组织SGZ和SVZ存在少量Brdu阳性细胞,对照组脑缺血再灌注3 d SGZ、SVZ和梗死皮质周边Brdu阳性细胞的数量开始增多,7 d达到高峰,11d后开始减少,18 d进一步下降.实验组与对照组相比,在各个时间点均能显著提高BrdU阳性细胞的数量(P＜0.01),而且增殖可以持续11d.结论脑缺血再灌注可激活脑内NSC的增殖,雌激素可以促进脑缺血再灌注多个区域NSC的增殖.     

TRPC1沉默对脑缺血大鼠神经干细胞迁移的影响

目的探讨瞬时受体电位通道1(TRPC1)沉默对脑缺血大鼠内源性神经干细胞增殖、迁移和分化的影响。方法 SD大鼠分为假手术组、脑缺血组、TRPC1沉默组(脑缺血+TRPC1沉默)和阴性对照组,以脑室内注射siRNA沉默TRPC1,以线栓法制作大鼠大脑中动脉脑缺血(MCAO)模型,脑缺血模型制作成功后,腹腔内注射Brdu标记内源性神经干细胞,分别于48 h、4 w后处死大鼠,行Brdu免疫组化染色、免疫荧光双标染色(Brdu/GFAP、Brdu/Neun)观察NSC的增殖、迁移和分化情况。结果脑缺血后48 h,脑缺血组和TRPC1沉默组SVZ区Brdu阳性表达均较假手术组明显增多(P0.01),但TRPC1沉默组Brdu阳性细胞数较缺血组低(P0.01)。脑缺血4 w后,缺血组与假手术组相比,皮质区具有更多的Brdu阳性细胞(P0.01),同样TRPC1沉默组Brdu阳性细胞数多于假手术组,但明显低于脑缺血组(P0.01);免疫荧光双标染色发现,脑缺血各组Brdu/GFAP、Brdu/Neun双阳性细胞的数量均比假手术组明显增高,但TRPC沉默组双阳性细胞显著少于脑缺血组和阴性对照组(P0.01)。结论 TRPC1沉默显著影响脑缺血大鼠SVZ区NSC的增殖、向脑缺血区迁移及向成熟细胞的分化。     

NMDA受体拮抗剂剂量与脑缺血再灌注大鼠海马内源性神经干细胞的增殖

背景：脑缺血再灌注后,过度释放的兴奋性氨基酸可通过NMDA受体激活内源性神经干细胞,促使其增殖、分化,修复神经细胞,但同时也导致细胞内钙离子超载,引起神经细胞的损伤。通过控制NMDA受体活化的程度,刺激内源性神经干细胞激活的同时把损伤减到最小。 目的：观察NMDA受体拮抗剂MK-801质量浓度对脑缺血再灌注大鼠海马内源性神经干细胞增殖的影响。 方法：健康雄性SD大鼠54只随机数字表法分为对照组(不进行任何处理)、手术组(缺血模型制作)及不同剂量MK-801组。采用大鼠四条血管阻断方法(Pulsinelli-4VO法)制备大鼠全脑缺血再灌注模型。不同浓度MK-801组在模型制作前30 min按照0.2,0.4,0.6,0.8,1.0 ,1.2 mg/kg侧脑室注射MK-801。Western-blot、RT-PCR技术检测各组nestin蛋白及mRNA水平及表达。 结果与结论：MK-801剂量在0.8 mg/kg以下时,nestin mRNA及蛋白的表达差异无显著性意义(P > 0.05),呈现高表达;当剂量为0.8 mg/kg时,可明显抑制内源性神经干细胞增殖;在0.8mg/kg以上,对神经干细胞的抑制作用随着剂量的升高呈递增趋势;在1.2 mg/kg时,大鼠有躁动、共济失调等严重不良反应。nestin mRNA表达结果与蛋白表达趋势相吻合。说明MK-801的剂量与脑梗死后神经功能的修复有一定的关系,实验中0.6 mg/kg是一个比较合适的实验应用剂量,在此剂量下既可使MK-801减少兴奋性氨基酸对神经元的毒性作用,保护神经细胞,又使内源性神经干细胞的增殖不受较大影响。     

左旋多巴诱导异动症大鼠模型纹状体棘状神经元电活动的研究

目的研究左旋多巴诱导异动症(levodopa induced-dyskinesias LID)大鼠模型纹状体棘状神经元的自发性电活动变化。方法帕金森病(Parkinson disease PD)大鼠模型应用左旋多巴(L-dopa)治疗28d诱发LID大鼠模型,29d L-dopa治疗前15min腹腔注射N-methyl-D-aspartic acid(NMDA)受体拮抗剂地佐环平(MK-801)1次。采用微电极细胞外记录技术检测大鼠模型纹状体棘状神经元的电生理活动。结果LID大鼠纹状体神经元的自发性电活动较对照组(P<0.01)及PD组(P<0.05)明显增多,MK-801治疗后显著减少(P<0.01)。结论纹状体棘状神经元的自发性电活动改变是LID的重要发病机制之一,NMDA受体拮抗剂可能通过逆转纹状体棘状神经元的电活动抑制LID的发生。     

地卓西平马来酸盐对雄性大鼠自发活动和前脉冲抑制及再认记忆的影响

目的 观察急性腹腔注射N-甲基-D-天冬氨酸(NMDA)受体拮抗剂地卓西平马来酸盐(MK-801)刘大鼠自发活动、感觉运动门控和物体再认记忆的影响,探讨MK-801模拟精神分裂症不同内表现型的适宜剂量.方法 成年雄性SD大鼠共104只,按照体质量采用分层随机化方法进行分组.(1)取SD大鼠48只,分为MK-801小剂量组、MK-801中剂量组、MK-801高剂量组和对照组,每组12只,观察不同剂量MK-801 (0.1、0.2、0.4 mg/kg)对大鼠自发活动的影响;(2)取SD大鼠32只,分为MK-801小剂量组、MK-801中剂量组、MK-801高剂量组和对照组,每组8只,观察不同剂量MK-801(0.1、0.2、0.4 mg/kg)对大鼠前脉冲抑制(PPI)的影响;(3)取SD大鼠24只,分为MK-801小剂量组和对照组,每组12只,观察小剂量MK-801 (0.1 mg/kg)对大鼠物体辨别测试的影响.结果 (1)中高剂量MK-801 (0.2,0.4 mg/kg)呈剂量依赖性诱导大鼠自发活动的增加以及PPI的损害(P＜0.05或P＜0.01),小剂量(0.1 mg/kg)组在自发活动和PPI上与对照组差异无统计学意义(P＞0.05).(2)小剂量MK-801组在物体辨别测试中对新物体的偏爱指数显著低于对照组[(57.79±10.66)％比(73.34±18.52)％,P＜0.05].结论 中高剂量MK-801可引起自发活动和感觉运动门控功能异常,而小剂量在排除运动系统异常的前提下可特异性地破坏大鼠的再认记忆,提示MK-801模拟精神分裂症的不同内表现型时应根据研究目的选择适宜剂量.     

N-甲基-D-天冬氨酸受体亚单位2B特异性拮抗剂对缺氧缺血性脑损伤新生大鼠脑室下区神经干细胞增殖的影响

目的:研究N-甲基-D-天冬氨酸受体(NMDAR)亚单位2B(NR2B)特异性拮抗剂(Ro 25-6981)对缺氧缺血性脑损伤(HIBD)新生大鼠脑室下区(SVZ)神经干细胞(NSCs)增殖的影响。方法:7 d龄新生SD大鼠随机分为Ro 25-6981组(HIBD前2 h,腹腔注射Ro 25-6981 10 mg.kg-1)、HIBD组(HIBD前2 h,腹腔注射等剂量生理盐水)和假手术组(仅游离右侧颈总动脉,不结扎)。采用免疫组化学染色检测SVZ Nestin表达量及BrdU阳性细胞数的变化。结果:HIBD组12h后Nestin表达量开始增多,48 h达峰值,之后缓慢下降;与其相比,Ro 25-6981组在12 h和24 h时下降明显(P<0.05)。HIBD组BrdU阳性细胞数在缺氧缺血3 h后缓慢上升,72 h达高峰;与其相比,Ro 25-6981组在各时间点BrdU阳性细胞表达均有所下降,以24、48和72 h减少明显,尤以72 h为著(P<0.05)。结论:Ro 25-6981能够降低HIBD新生大鼠SVZ Nestin的表达及Brdu阳性细胞数,对SVZ NSCs增殖起抑制作用,提示NR2B参与并促进HIBD引起的SVZ NSCs的增殖。     

快感缺失相关的精神分裂症阴性症状动物模型的研究

目的在精神分裂症NMDA受体功能低下神经发育假说基础上,建立快感缺失相关的精神分裂症阴性症状动物模型。方法将新生大鼠随机分6组,每组8～10只,NS-NS组,NS-HAL(氟哌啶醇)组,NS-RIS(利培酮)组,MK801-NS组,MK801-HAL组,MK801-RIS组。大鼠出生后第5～14天分别给予生理盐水及MK-801,在大鼠成年期给予抗精神病药利培酮及氟哌啶醇干预,亚慢性给药2周后进行糖水实验,检测糖水消耗量及糖水偏爱度。结果新生期暴露于MK-801的动物糖水偏爱度(0.63±0.046)显著低于对照组(0.838±0.047),P0.05,利培酮干预组动物的糖水偏爱度(0.86±0.060)显著高于氟哌啶醇干预组(0.631±0.055),P0.05。结论新生期暴露于NMDA受体拮抗剂MK-801可导致动物出现快感缺失,利培酮可逆转该损害。NMDA受体功能低下神经发育模型可作为快感缺失相关的精神分裂症阴性症状动物模型。     

小剂量MK-801对大鼠参照记忆、空间工作记忆和逆反学习能力的影响

目的 探讨腹腔注射N-甲基-D-天冬氨酸 (NMDA )受体拮抗剂地卓西平马来酸盐(MK-801)对大鼠认知功能的影响.方法 成年雄性SD大鼠随机分为MK-801组和对照组,分别腹腔注射小剂量生理盐水或MK-801(0.1 mg/kg)20 min后在Morris水迷宫中评定MK-801对大鼠参照记忆、空间工作记忆和逆反学习能力的影响.结果 参照记忆任务中,与对照组相比MK-801组逃避潜伏期延长(P<0.05),且在目标象限的探索时间百分比[(22.7±2.9)%]与相邻象限[(24.0±0.9)%]和对立象限[(29.3±2.4)%]的差异无统计学意义 (P>0.05);空间工作记忆任务中,对照组匹配试次潜伏期显著短于样本试次[(37.6±6.0) vs (61.5±6.3),P<0.05],而MK-801组两试次潜伏期差异无统计学意义[(53.8±7.8) vs (62.2±7.1),P>0.05];逆反学习任务中,与对照组相比MK-801组潜伏期明显延长(P<0.05),且在空间探索中新旧目标象限探索时间百分比差值小于对照组[(-0.01±4.7) vs (23.5±6.2),P<0.01].结论 腹腔注射小剂量MK-801破坏了大鼠的参照记忆、空间工作记忆和逆反学习,提示其在多个认知维度上可模拟精神分裂症患者的认知缺陷.     

NMDA receptor blockade attenuates the haloperidol induction of Fos protein in the dorsal but not the ventral striatum.

Neuroleptic blockade of dopamine receptors is known to produce an increase in the expression of Fos. This increase may be related to elevations in glutamate transmission which in turn activates N-methyl-D-aspartate (NMDA) receptors. In the present study, we examine the role of these receptors in the haloperidol-induced augmentation of Fos in the caudate-putamen and nucleus accumbens of Wistar rats. Animals were divided into four groups for each experiment and each was injected either with saline; a noncompetitive NMDA antagonist, dizocilpine maleate (MK801, 5 mg/kg); haloperidol (0.5 mg/kg); or MK801 followed by an injection of haloperidol. Fos-immunoreactive cells appear in large numbers in all parts of the striatum 3 h after the administration of haloperidol. Pretreatment with MK801 attenuates the haloperidol-induced increase in Fos in the caudate-putamen. However, antagonism of the NMDA receptor does not significantly reduce the density of Fos-immunoreactive cells in any territory of nucleus accumbens, i.e., shell, core, or rostral pole. These data suggest that haloperidol acts in an NMDA-dependent manner in the caudate-putamen, but independently in parts of nucleus accumbens traditionally considered to be targets of antipsychotic drugs.     

Neonatal exposure to MK‐801 reduces mRNA expression of mGlu3 receptors in the medial prefrontal cortex of adolescent rats

Schizophrenia is considered as a “neurodegenerative” and “neurodevelopmental” disorder, the pathophysiology of which may include hypofunction of the N‐methyl‐d ‐aspartate receptor (NMDA‐R) or subsequent pathways. Accordingly, administration of NMDA‐R antagonists to rodents during the perinatal period may emulate some core pathophysiological aspects of schizophrenia. The effect of 4‐day (postnatal day; PD 7–10) administration of MK‐801, a selective NMDA‐R antagonist, on gene expression in the medial prefrontal cortex (mPFC), hippocampus, and amygdala was evaluated using quantitative polymerase chain reaction methods. Specifically, we sought to determine whether genes related to Glu transmissions, for example those encoding for NMDA‐Rs, metabotropic Glu receptors (mGluRs), or Glu transporters, were altered by neonatal treatment with MK‐801. Model rats showed downregulation of the mGluR3 subtype in the mPFC around puberty, especially at PD 35 in response to MK‐801 or during ontogenesis without pharmacological manipulations. Genes encoding for other mGluRs subtypes, that is NMDA‐Rs and Glu transporters, were not affected by the neonatal insult. These results suggest that NMDA‐R antagonism in the early course of development modulates the expression of mGluR3 in mPFC around puberty. Thus, mGluR3 may serve as a potential target to prevent the onset and progression of schizophrenia. Synapse 68:202–208, 2014 . © 2014 Wiley Periodicals, Inc.     

MK-801建立谷氨酸功能低下精神分裂症大鼠模型的研究

目的 用N-甲基-D-天门冬氨酸(NMDA)非竞争性受体拮抗剂地卓西平马来酸盐(MK801)建立具有类精神分裂症症状的大鼠模型.方法 24只SD大鼠随机分为MK801组、生理盐水组和正常对照组,每组各8只.MK801组的大鼠每天腹膜腔内注射0.5 mg/kg(给药体积为10 mL/kg)MK801共6 d以建立精神分裂症模型,生理盐水组给予等体积生理盐水.用自发活动、强迫游泳试验、逃避性抑制(inhibitory avoidance,IA)试验以及海马神经生长因子表达评价该模型.结果 MK801组、生理盐水组和对照组的大鼠10min自发活动总路程分别为(3127±381)cm、(935±196)cm、(1060±243)cm,游泳不动时间分别为(147±18)s、(58±10)s、(52±10)s.3组的自发活动和游泳不动时间差异均有统计学意义(F=149.7,P<0.01;F=122.6,P<0.01),MK801组的自发活动较另两个组均增加(P<0.01),而游泳不动时间延长(P<0.01).3组的24 h IA的记忆潜伏期也有明显差异(F=5.2,P<0.05),MK801组的记忆潜伏期[(26±10)s]较生理盐水组[(47±16)s]和对照组[(46±14)s]均缩短(P<0.05).而且,MK801组海马神经生长因子表达明显下调.结论 连续给予高剂量MK801诱导的大鼠谷氨酸功能低下模型不仅具有类精神分裂症症状.而且还存在神经生物学改变,可作为模拟精神分裂症的模型.     

补肾壮阳胶囊对精神分裂症模型大鼠海马胶质细胞源性神经营养因子表达的影响

目的 探讨补肾壮阳胶囊(WSKY)对地卓西平马来酸盐(MK801)建立的精神分裂症模型大鼠海马胶质细胞源性神经营养因子(GDNF)表达的影响.方法 将40只6周龄SD雄性大鼠随机分为3组:对照组(生理盐水腹腔注射+生理盐水灌胃)、模型组(M K801腹腔注射+生理盐水灌胃)及WSKY+MK801组(MK801腹腔注射+WSKY灌胃,而根据WSKY剂量的不同又分为3个亚组);各组相应处理两周后运用Western Blot和RT-PCR技术分别检测各组大鼠海马区GDNF蛋白及mRNA的表达.结果 与对照组相比较,模型组的GDNF蛋白及mRNA的表达下降,差异有统计学意义(P<0.05);而与模型组相比,WSKY+MK801组中较高剂量WSKY可致GDNF蛋白及其mRNA的表达增加,差异有统计学意义(P<0.05).结论 MK801可致大鼠海马GDNF表达减少,而补肾壮阳胶囊可上调大鼠海马GDNF的表达.     

Hippocampal CRF,NE, and NMDA system interactions in memory processing in the rat

In the present study, we investigated the neural mechanisms of corticotropin-releasing factor (CRF) and the interactions among CRF, norepinephrine (NE), and N-methyl-D-aspartate (NMDA) systems in the dentate gyrus (DG) of hippocampus in modulating the memory process of rats. One-way passive avoidance task was adopted. Results indicated that CRF (80 ng), when directly injected into the DG, consistently and significantly enhanced memory retention in rats. The noradrenergic neurotoxin DSP-4, at a high dose (4 μg), impaired memory. DSP-4 at a moderate dose (2 μg), which did not affect retention alone, antagonized the memory-enhancing effect of CRF. Similarly, the ß-adrenergic antagonist propranolol, at a high dose (8 μg), reduced retention. At a low dose (80 ng), which did not markedly affect retention by itself, propranolol also prevented the memory-improving effect of CRF. Moreover, direct NE infusions to the DG significantly improved retention performance in a dose-sensitive manner. Coadministration of CRF and NE did not further enhance retention. These results together suggest that CRF and NE facilitated memory probably through the same instead of independent mechanisms. In contrast, the selective NMDA receptor antagonists 2-amino-5-phosphonopentanoate (AP5) and MK801, at high doses markedly impaired memory retention (0. 8 and 3. 2 μg for AP5, 2 and 10 μg for MK801). At a dose of MK801 that did not significantly alter retention alone (80 ng), it completely blocked the memory-facilitating effect of CRF. These results indicate that CRF enhanced memory indirectly through NMDA receptor mediation also. Finally, MK801 at 80 ng also successfully antagonized the memory-facilitating effect of NE in the DG. We have demonstrated that MK801, at the dose chosen for interaction studies, did not markedly alter locomotor activity. These results together suggest that CRF, through a presynaptic facilitation mechanism, possibly facilitates NE release in the DG: increased NE release and stimulation of ß-adrenergic receptors in the DG result in NMDA receptor activations in the same area. This sequence of events enhance the memory consolidation process in the hippocampus and explained the neural mechanism of CRF in facilitating retention performance in rats. The same neuropeptide/neurotransmitter interactions may have other physiological and neuropathological implications. © 1993 Wiley-Liss, Inc.     

In vitro and in vivo characterization of the NMDA receptor-linked strychnine-insensitive glycine site.

Modulation of the NMDA receptor by the strychnine-insensitive glycine site was studied both in vitro and in vivo. In vitro the glycinergic stimulation of [3H]MK801 binding was measured in three different rat forebrain membrane preparations. An increased association rate of [3H]MK801 in the presence of glycine was observed. The binding of the radioligand was also enhanced by D-serine, whereas L-serine was less potent. The concentration-effect curves were shifted to the right by the glycine antagonist 7-chlorokynurenic acid (7CKA). In vivo modulation of the N-methyl-D-aspartate (NMDA) receptor was studied using NMDA induced convulsions in 7 day old rats. The NMDA effect was blocked by (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten,5,10-imine maleate (MK801) and D-(-)-2-amino-5-phosphono-pentanoic acid (AP5). The effect of a submaximal dose of NMDA was dose-dependently potentiated by 1-10 mg/kg D-serine, whereas higher doses of L-serine were needed to obtain a similar effect. 7CKA did not affect NMDA-induced convulsions but reduced the D-serine potentiation of NMDA responses. This study illustrates the ability of the strychnine-insensitive glycine site to modulate the NMDA receptor function both in vitro and in vivo.     

Effect of an NMDA receptor antagonist on the wind-up of neurons in the trigeminal oralis subnucleus

Extracellular recordings of convergent neurons of the oralis subnucleus of the trigeminal sensory complex were performed in paralysed rats under halothaneN₂OO₂ anesthesia using glass micropipettes. The effects of MK801, a noncompetitive NMDA receptor antagonist, were observed on the increased cell activity (wind-up), triggered by the repetition, at a low frequency (0.66 Hz) and high intensity (3 times the threshold of C-fiber response), of electrical stimulation of the receptive field. Successive cumulative doses (up to 1 mg/kg) of MK801 i.v. resulted in a dose-dependent decrease in the responses related to C-fiber input (11 cells). A single dose of 1 mg/kg applied in four cells had effects similar to the 1 mg/kg dose given cumulatively. Three units were either weakly or not modified by MK801. In a second experiment, recordings were performed in 12 cells for 80 min after an injection of a small dose of MK801 (0.15 mg/kg). C input was not significantly modified by the antagonist. The effects of MK801 on the first part of the wind-up response (wind-up proper) peaked between 15 and 50 min and returned to control values at about 80 min. The effects on the postdischarge followed approximately the same time course. It is concluded that despite being devoid of substantia gelatinosa, the oralis subnucleus contains neurons that display an NMDA receptor-linked wind-up similar to the phenomenon described in the dorsal horn of the spinal cord.     

Association between inflammation and nigral neuronal damage following striatal excitotoxic lesion

We examined the expression of TNF-alpha within the substantia nigra pars reticulata (SNR) following intrastriatal injection of quinolinic acid (QA) and studied the effect of rolipram, a TNF-alpha-inhibitor, on the secondary neuronal damage. QA (240 nmol in 1 microl) was injected stereotactically into the striatum of male Wistar rats. After survival of 1, 3 or 10 days, the animals were sacrificed and immunohistochemical staining with an antibody against TNF-alpha was performed. From day 1 to day 10 after striatal QA injection TNF-alpha positive cells were observed within ipsilateral substantia nigra which were neither present on the contralateral side nor in sham-operated controls. Double labeling with antibodies against TNF-alpha and NeuN, keratan sulfate proteoglycan or GFAP displayed a good overlap between TNF-alpha and NeuN, which suggests that TNF-alpha positive cells are neurons. For the pharmacological approach, three groups of QA rats were treated intraperitoneally with either solvent (n=5), the NMDA receptor antagonist MK 801 (4 mg/kg, n=6) or the TNF-alpha inhibitor rolipram (0.3 mg/kg, n=6), which was started 24 h after QA-injection and continued with daily applications for 14 days. The amount of striatal damage did not differ between the three groups. The number of intact neurons within the ipsilateral substantia nigra of the solvent treated group was reduced by approximately 30% compared to the contralateral side. Both MK 801 and rolipram ameliorated this secondary damage and reduced the number of TNF-alpha positive cells. The observed association between expression of TNF-alpha and secondary neuronal damage within the substantia nigra induced by intrastriatal QA application might hint towards an involvement of this cytokine in transneuronal degeneration.     

Effects of antipsychotic treatments and D-serine supplementation on the electrophysiological activation of midbrain dopamine neurons induced by the noncompetitive NMDA antagonist MK 801

The acute administration of the noncompetitive glutamate N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine (MK 801) is known to increase central dopaminergic activity in rats and to elicit schizophreniform behavior in human. The current study was undertaken to compare the effects of different acute or chronic neuroleptic treatments, on the response of ventral tegmental area dopamine (DA) neurons to MK 801, using the in vivo electrophysiological paradigm in anesthetized preparations. Sprague Dawley male rats were treated, acutely or chronically during 3 weeks, with saline, olanzapine (10 mg/kg), haloperidol (1 mg/kg) or the combination of haloperidol with D-serine (1 mg/kg/300 mg/kg), a gliotransmitter coagonist of the NMDA receptor that has been shown to improve the efficacy of typical neuroleptics. In control animals, the acute administration of MK 801 (0.5 mg/kg, i.v.) increased significantly both the firing and burst activity of DA neurons by 20 and 26%, respectively, the latter effect being partially reversed by the selective 5-HT2A antagonist M 100,907 (0.4 mg/kg, i.v.). The acute preadministration of haloperidol (1 mg/kg, i.p.) and olanzapine (10 mg/kg, i.p.) failed to prevent or reverse the activatory effect of MK 801 on firing activity. On the other hand, MK 801-induced burst activity, was partially prevented by olanzapine, but not by haloperidol pretreatment. All antipsychotic treatments, when administered chronically, prevent the activatory effect of MK 801 on both firing and burst activity, and occasionally convert the response to MK 801 on burst activity to an inhibitory response, the latter occurring more predominantly in rats treated with the combination haloperidol/D-serine. These results suggest that a chronic antipsychotic regime alters the function of the NMDA receptors that tonically control the firing activity of midbrain dopaminergic neurons.     

Kindled seizure-evoked somatostatin release in the hippocampus: inhibition by MK-801

The aim of this study was to evaluate the contribution of ionotropic glutamate receptors to kindled seizure-evoked somatostatin release in the hippocampus, using a microdialysis approach. Basal and amygdala stimulation-evoked somatostatin-like immunoreactivity (-LI) release was significantly greater in kindled compared to naive rats. In naive rats, neither hippocampal perfusion with the selective AMPA/kainate receptor antagonist GYKI 52466 nor with the selective NMDA receptor antagonist MK-801 affected behavior, EEG, or somatostatin-LI release. In kindled rats, GYKI 52466 was still devoid of any effect, while MK-801 significantly decreased stimulus-evoked (but not basal) somatostatin-LI efflux. MK-801 produced identical effects when injected i.p. This study provides the first direct evidence that kindled seizure-evoked somatostatin release in the hippocampus is partly NMDA receptor dependent.