GR82334对强电流刺激大鼠隐神经增强扣带回前部Fos蛋白表达的影响

目的研究尾静脉或蛛网膜下腔注射神经激肽(neurokinin,NK)-1受体拮抗剂GR82334对强电流刺激大鼠隐神经(saphenous nerve,SN)增强扣带回前部(anterior cingulate gyrus,ACG)Fos蛋白表达的影响。方法应用免疫组化技术进行实验研究。结果强电流刺激大鼠SN引起ACG Fos蛋白表达显著增强;尾静脉或蛛网膜下腔注射GR82334拮抗了强电流刺激大鼠SN引起的ACG Fos蛋白表达的显著增强。然而,蛛网膜下腔注射GR82334并没有完全拮抗强电流刺激大鼠SN引起的ACG Fos蛋白表达的显著增强。结论大鼠SN传导的伤害性信息能够到达ACG,激活c-fos基因表达;外周NK-1受体与中枢NK-1受体参与大鼠SN传入信息引起的ACG Fos蛋白表达增强的过程,但是,还存在其他递质和受体参与的大鼠SN信息传入的其它中枢通路引起ACG Fos蛋白表达的显著增强。     

CNQX对伤害性刺激隐神经诱发大鼠脊髓Fos蛋白表达的影响

目的 探讨伤害性刺激隐神经（SN）能否诱发脊髓神经元Fos蛋白表达及发生机制.方法 应用免疫组化方法观察伤害性刺激SN和尾静脉注射谷氨酸非NMDA受体拮抗剂（CNQX）后诱发脊髓神经元Fos蛋白表达的变化.结果 伤害性刺激SN后,诱导脊髓神经元Fos蛋白表达显著增强,CNQX拮抗了Fos蛋白表达的显著增强.结论 以伤害性刺激SN模拟躯体痛后,CNQX拮抗了伤害性刺激SN引起的脊髓神经元Fos蛋白表达的显著增加,表明非NMDA受体在躯体痛的调控中起到了重要的作用.     

吗啡、MK-801对电刺激隐神经引起大鼠ACG多巴胺含量增高的影响

目的研究皮下注射吗啡、静脉注射N-甲基-D-天冬氨酸(N-methyl-D-aspartate,NMDA)受体拮抗剂5-甲基二氢丙环庚烯马来酸(MK-801)对电刺激隐神经(saphenous nerve,SN)引起大鼠扣带回前部(anterior cingulate gyrus,ACG)多巴胺含量增高的影响,以及MK-801对吗啡作用的影响。方法应用高效液相色谱-电化学检测技术进行实验研究。结果电刺激SN引起ACG多巴胺含量显著增高;皮下注射吗啡抑制电刺激SN引起的ACG多巴胺含量的显著增高;静脉注射MK-801能够拮抗电刺激SN引起的ACG多巴胺含量的显著增高,并且能够增强吗啡抑制电刺激SN引起的ACG多巴胺含量的显著增高。结论 SN传导的伤害性信息能够到达ACG,激活ACG多巴胺能神经元,释放多巴胺,谷氨酸NMDA受体参与此过程;吗啡抑制ACG多巴胺能神经元的活动;MK-801增强吗啡的抑制作用。     

中缝背核注射L-NAME抑制炎性痛大鼠脊髓Fos的表达

目的 观察中缝背核(DRN)内一氧化氮合酶(NOS)对炎性痛大鼠脊髓伤害性信息传递的调控作用.方法 建立大鼠单侧足底甲醛炎性痛模型,采用行为学、c-Fos免疫组织化学及烟酰胺腺嘌呤二核苷酸磷酸黄递酶(NADPH-d)组织化学技术,观察甲醛诱发炎性痛后大鼠DRN内NADPH-d、NADPH-d/Fos双标阳性神经元数量的变化;同时观察DRN内预先给予NOS抑制剂L-NAME对甲醛致痛大鼠疼痛评分及脊髓Fos蛋白表达的影响.结果 单侧足底注射甲醛后,DRN内NADPH-d、NADPH-d/Fos双标阳性神经元的数量增加.DRN内预先注射L-NAME降低炎性痛大鼠的疼痛学评分及脊髓Fos阳性神经元的数量.结论 DRN内NOS可能促进甲醛炎性痛大鼠脊髓伤害性信息的传递.     

丙泊酚对大鼠海马CA1区长时程增强的影响

目的：研究丙泊酚对大鼠海马CA1区长时程增强（LTP）表达的影响,并探讨其机制。方法：63只戊巴比妥钠麻醉大鼠分多组,分别观察腹腔注射丙泊酚20mg/kg对海马CA1区树突层兴奋性突触后膜电位（EPSP）、LTP表达的影响以及与D-2-氨基-5-磷酸戊酸（APV）和6-氰基-7-硝基喹啉-2,3-二酮（CNQX）合用时对LTP表达的影响。结果：各组基础EPSP幅值稳定;高频刺激（HFS）前应用丙泊酚引出的LTP与对照组相当（P〉0.05）,HFS后LTP幅值明显低于对照组（P〈0.01）;丙泊酚合用APV后不能引出LTP,合用CNQX后幅值一过性升高后,迅速下降并低于基线（P〈0.05）。结论：丙泊酚20mg/kg腹腔注射不影响戊巴比妥钠麻醉大鼠海马CA1区N-甲基-D-门冬氨酸（NMDA）受体依赖型LTP诱导,但可影响其维持;其机制与阻滞α-氨基-3-羟基-5-甲基恶唑-4-丙酸（AMPA）受体有关,与NMDA受体功能状态无关。     

NMDA和非NMDA受体参与介导猫脊髓内脏伤害性信息传递(英文)

目的:研究NMDA(N-methyl-D-aspartic acid)和非NMDA受体在介导脊髓内脏痛传入中的作用,方法:气球膨胀(3-15 kPa,20 s)麻醉猫结-直肠诱发脊髓背角痛敏神经元发放,结果:1)扩张结-直肠引起神经元发放增加的为兴奋性型:17个SLA型(短潜伏期突然增加);11个SLS型(短潜伏期渐增);9个LL型(长潜伏期),15个神经元属于抑制性的Inh型,2)67.6％,78.4％和59.5％的膨胀肠诱发兴奋的神经元,分别被微电泳NMDA、使君子酸(QA)和海人藻酸(KA)激活;60％,86.7％和53.3％的Inh神经元也分别被3个酸激活.3)微电泳NMDA受体拮抗剂d,l-2-amino-5-phosphonovalemte(APV)和非NMDA受体拮抗剂6,7-dinitro-quinoxaline-2,3-dione(DNQX),分别使兴奋性反应减少35％±10％和65％±14％,DNQX明显强于APV(P<0.05).DNQX使3/7个Inh神经元抑制翻转30％-50％,而APV无效,结论:NMDA和非NMDA受体均参与介导脊髓内脏伤害性信息传递,而非NMDA受体的作用更强。 (责任编辑 李颖)     

抗抑郁剂慢性给药对强迫游泳大鼠下丘脑c-Fos蛋白表达水平的下调作用

应用c-Fos蛋白免疫组织化学定位观察的方法, 在强迫游泳大鼠抑郁模型上, 观察地昔帕明(5, 20 mg·kg^-1), 吗氯贝胺 (10, 40 mg·kg^-1)和氟西汀 (5, 20 mg·kg^-1) 慢性给药 (ip 每日1次, 连续7 d)对大鼠游泳不动时间和下丘脑核团c-Fos蛋白表达水平的影响. 结果表明: 强迫游泳可使大鼠下丘脑多个核团的c-Fos蛋白表达水平明显升高, 而地昔帕明, 吗氯贝胺, 氟西汀明显缩短强迫游泳大鼠的不动时间, 并选择性地使强迫游泳诱导增加的下丘脑室旁核Fos样免疫阳性神经元数目明显减少. 提示下丘脑室旁核可能是介导抗抑郁剂抑制大鼠绝望行为的中枢部位之一. Fos蛋白可能是不同类型抗抑郁剂共同的受体后信号转导物质.     

NO介导吗啡戒断大鼠脊髓Fos蛋白和NMDA_(1A)受体mRNA表达的增加

目的:观察NO在纳洛酮催促吗啡戒断大鼠脊髓神经元活动变化中的作用。方法:采用Fos免疫组织化学、NADPH-d组织化学、Fos/NADPH-d双标、鞘内注射、反义寡核苷酸和RT-RCR技术。结果:急性应用纳洛酮和慢性应用吗啡对大鼠脊髓Fos蛋白及NADPH-d阳性神经元表达无明显影响,二者也无Fos/NADPH-d双标神经元表达;纳洛酮催促吗啡戒断大鼠脊髓Fos蛋白、NADPH-d阳性神经元、纤维和终末表达明显增加,且出现Fos/NADPH-d双标神经元表达。预先鞘内注射nNOS反义寡核苷酸明显降低吗啡戒断症状评分,减少吗啡戒断大鼠脊髓Fos蛋白及NMDA_(1A)R mRNA表达。结论:NO介导吗啡戒断大鼠脊髓Fos和NMD_(1A)R mRNA表达的增加。     

匹诺塞林对体外共培养海兔SN/L7神经元电生理活动的作用

目的研究匹诺塞林(PNCB)对海兔神经元共培养体系(SN/L7)的电生理效应,探讨可能的作用机制。方法体外共培养海兔(aplysia)的感觉神经元(SN)和运动神经元(L7),使其互相接触形成突触连接。细胞培养至d 5,给予不同浓度的PNCB刺激,考察药物对SN/L7兴奋性突触后电位(EPSP)的影响,随后撤去药物,观察EPSP的恢复情况。另取细胞,在PNCB孵育后加入0.005 mmol.L-15-羟色胺(5-HT),观察SN/L7对5-HT的反应性的变化。结果 PNCB作用5 min,使SN/L7的EPSP幅值降低。药物浓度低于0.1 mmol.L-1时,作用强度与药物剂量呈负线性关系(r>0.995),在0.1～0.4 mmol.L-1的浓度范围内,作用强度与药物剂量呈正线性关系(r>0.998);撤去药物后,SN/L7的EPSP幅值可恢复至初始值。PNCB使SN/L7对5-HT的反应性消失,撤去药物后,该反应性得以恢复。结论 PNCB可逆地抑制体外共培养的海兔SN/L7神经元突触的兴奋性传导,并可逆地抑制SN/L7对5-HT的反应性。这一效应可能与突触后膜的谷氨酸受体有关。     

AMPA受体成像与突触可塑性

在中枢神经系统中,α-氨基-3-羟基-5-甲基-4-异唑丙酸(AMPA)型谷氨酸受体介导大部分快速兴奋性神经突触传递,受体插入和离开突触的转运过程高度动态化,该过程的调节对多种形式的突触可塑性起至关重要的作用。而突触可塑性被认为是包括学习、记忆在内的大脑高级认知行为的关键分子机制。研究表明,当AMPA受体或调控AMPA受体转运的蛋白发生遗传突变时,会导致各种各样的疾病,包括自闭症、精神分裂症、阿尔茨海默病以及智力障碍等疾病。因此,阐明AMPA受体转运和功能的调控对于理解大脑高级功能有重要意义。以前研究结果表明,利用连有荧光蛋白标签的AMPA受体,可以直接观察到受体在膜上的转移过程。大多数研究是在体外的原代神经元培养或急性脑片上进行的,令人欣喜的是,最近,活体内突触蛋白的可视化得以实现,为研究突触可塑性提供了崭新的手段。本文主要讨论AMPA受体转运领域的重要发现,阐述体外成像和体内成像技术的发展对突触可塑性研究的贡献,并对该领域未来的发展进行展望。     

Resolution, absolute stereochemistry and molecular pharmacology of the enantiomers of ATPA

(RS)-2-Amino-3-(5-tert-butyl-3-hydroxy-4-isoxazolyl)propionic acid (ATPA), an analogue of (RS)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA), has previously been shown to be a relatively weak AMPA receptor agonist and a very potent agonist at the GluR5 subtype of kainic acid-preferring (S)-glutamic acid ((S)-Glu) receptors. We report here the separation of (+)- and (−)-ATPA, obtained at high enantiomeric purity (enantiomeric excess values of 99.8% and >99.8%, respectively) using chiral chromatography, and the unequivocal assignment of the stereochemistry of (S)-(+)-ATPA and (R)-(−)-ATPA. (S)- and (R)-ATPA were characterized in receptor binding studies using rat brain membranes, and electrophysiologically using the rat cortical wedge preparation and cloned AMPA-preferring (GluR1, GluR3, and GluR4) and kainic acid-preferring (GluR5, GluR6, and GluR6+ KA2) receptors expressed in Xenopus oocytes. In the cortical wedge, (S)-ATPA showed AMPA receptor agonist effects (EC₅₀=23 μM) approximately twice as potent as those of ATPA. (R)-ATPA antagonized depolarizations induced by AMPA (K_i=253 μM) and by (S)-ATPA (K_i=376 μM), and (R)-ATPA antagonized the biphasic depolarizing effects induced by kainic acid (K_i=301 μM and 1115 μM). At cloned AMPA receptors, (S)-ATPA showed agonist effects at GluR3 and GluR4 with EC₅₀ values of approximately 8 μM and at GluR1 (EC₅₀=22 μM), producing maximal steady state currents only 5.4–33% of those evoked by kainic acid. (R)-ATPA antagonized currents evoked by kainic acid at cloned AMPA receptor subtypes with K_i values of 33–75 μM. (S)-ATPA produced potent agonist effects at GluR5 (EC₅₀=0.48 μM). Due to desensitization of GluR5 receptors, which could not be fully prevented by treatment with concanavalin A, (S)-ATPA-induced agonist effects were normalized to those of kainic acid. Under these circumstances, maximal currents produced by (S)-ATPA and kainic acid were not significantly different. (R)-ATPA did not attenuate currents produced by kainic acid at GluR5, and neither (S)- nor (R)-ATPA showed significant effects at GluR6. (S)-ATPA as well as AMPA showed weak agonist effects at heteromeric GluR6+KA2 receptors, whereas (R)-ATPA was inactive. Thus, (S)- and (R)-ATPA may be useful tools for mechanistic studies of ionotropic non-NMDA (S)-Glu receptors, and lead structures for the design of new subtype-selective ligands for such receptors.     

Effects of CNQX and MPEP on sensitization to the rewarding effects of morphine

The present study was conducted to evaluate the influence of the glutamatergic receptors α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and metabotropic glutamate 5 (mGlu5) receptors on sensitization to the rewarding effects of morphine. The effects of pre-treatment with saline or 20 mg/kg morphine plus the AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (5 or 10 mg/kg) or the metabotropic Glu5 receptor antagonist 6-methyl-2-(phenylethynyl)-pyridine (MPEP) (5 or 10 mg/kg) on the place conditioning induced by a low dose of morphine (2 mg/kg) were assessed. The 2 mg/kg dose of morphine was ineffective in animals pre-treated with saline but induced a clear conditioned place preference (CPP) in mice pre-treated with morphine alone and morphine plus any of the MPEP doses or the lowest dose of CNQX. Conversely, animals pre-treated with morphine plus 10 mg/kg of CNQX did not acquire CPP. Our results suggest that AMPA glutamate receptors are involved in the development of sensitization to the conditioned rewarding effects of morphine.     

Functional role of the endocannabinoid system and AMPA/kainate receptors in 5-HT2A receptor-mediated wet dog shakes

These experiments sought to determine the influence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptors and the endocannabinoid system in the functional expression of the serotonin (5-HT) type 2A receptor-mediated wet dog shake response. Male Long-Evans rats were pretreated with either 1 mg/kg i.p. of the 5-HT(2A/2C) receptor antagonist ketanserin; 1, 10 or 30 mg/kg i.p. of the AMPA/kainate antagonist 6,7-dinitroquinnoxaline-2,3-dione (DNQX); 1, 5 or 10 mg/kg i.p. of the endocannabinoid uptake inhibitor AM404; or 1, 5 or 10 mg/kg i.p. of the cannabinoid CB(1) receptor antagonist AM 251 prior to injection of the 5-HT(2A/2C) receptor agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI, 1 mg/kg i.p.). Results demonstrated that 10 mg/kg of AM404 significantly reduced the expression of DOI-induced wet dog shakes, but lower doses were ineffective. Administration of AM251 did not induce wet dog shakes behavior when administered alone, but significantly potentiated DOI-induced wet dog shaking behavior at a dose of 10 mg/kg. Pretreatment with DNQX significantly reduced the expression of DOI-induced wet dog shakes at all doses tested. These data suggest that AMPA/kainate receptors play a role in the mediation of 5-HT(2A) receptor activity, whereas the endocannabinoid system may act as a regulatory buffer system during periods of elevated activity, but not under basal conditions.     

Mutual enhancement of central neurotoxicity induced by ketamine followed by methamphetamine

We hereby report that repeated administration of ketamine (350 mg/kg in total) and methamphetamine (30 mg/kg in total) causes specific glutamatergic and dopaminergic neuron deficits, respectively, in adult mouse brain. Acute ketamine did not affect basal body temperature or the later methamphetamine-induced hyperthermia. However, pretreatment with repeated doses of ketamine aggravated methamphetamine-induced dopaminergic terminal loss as evidenced by a drastic decrease in the levels of dopamine, 3,4-dihydroxyphenylacetic acid, and dopamine transporter density as well as poor gait balance performance. In contrast, methamphetamine-induced serotonergic depletion was not altered by ketamine pretreatment. Likewise, the subsequent treatment with methamphetamine exacerbated the ketamine-induced glutamatergic damage as indicated by reduced levels of the vesicular glutamate transporter in hippocampus and striatum and poor memory performance in the Morris water maze. Finally, since activation of the D1 and AMPA/kainate receptors has been known to be involved in the release of glutamate and dopamine, we examined the effects of co-administration of SCH23390, a D1 antagonist, and CNQX, an AMPA/kainate antagonist. Intraventricular CNQX infusion abolished ketamine's potentiation of methamphetamine-induced dopamine neurotoxicity, while systemic SCH23390 mitigated methamphetamine's potentiation of ketamine-induced glutamatergic toxicity. We conclude that repeated doses of ketamine potentiate methamphetamine-induced dopamine neurotoxicity via AMPA/kainate activation and that conjunctive use of methamphetamine aggravates ketamine-induced glutamatergic neurotoxicity possibly via D1 receptor activation.     

Involvement of AMPA receptors in the antidepressant-like effects of lithium in the mouse tail suspension test and forced swim test

In addition to its clinical antimanic effects, lithium also has efficacy in the treatment of depression. However, the mechanism by which lithium exerts its antidepressant effects is unclear. Our objective was to further characterize the effects of peripheral and central administration of lithium in mouse models of antidepressant efficacy as well as to investigate the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors in these behaviors. We utilized the mouse forced swim test (FST) and tail suspension test (TST), intracerebroventricular (ICV) lithium administration, AMPA receptor inhibitors, and BS3 crosslinking followed by Western blot. Both short- and long-term administration of lithium resulted in robust antidepressant-like effects in the mouse FST and TST. Using ICV administration of lithium, we show that these effects are due to actions of lithium on the brain, rather than to peripheral effects of the drug. Both ICV and rodent chow (0.4% LiCl) administration paradigms resulted in brain lithium concentrations within the human therapeutic range. The antidepressant-like effects of lithium in the FST and TST were blocked by administration of AMPA receptor inhibitors. Additionally, administration of lithium increased the cell surface expression of GluR1 and GluR2 in the mouse hippocampus. Collectively, these data show that lithium exerts centrally mediated antidepressant-like effects in the mouse FST and TST that require AMPA receptor activation. Lithium may exert its antidepressant effects in humans through AMPA receptors, thus further supporting a role of targeting AMPA receptors as a therapeutic approach for the treatment of depression.     

Cyclothiazide and AMPA receptor desensitization: analyses from studies of AMPA-induced release of [3H]-noradrenaline from hippocampal slices

1. Responses in brain produced by the activation of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) subtype of ionotropic receptor for L-glutamate are often rapidly desensitizing. AMPA-induced desensitization and its characteristics, and the potentiating effect of cyclothiazide were investigated in vitro by analysing AMPA-induced release of [³H]-noradrenaline from prisms of rat hippocampus.
2. AMPA (1–1000 μM) stimulated the release of [³H]-noradrenaline in a concentration-dependent manner that was both calcium-dependent and tetrodotoxin-sensitive, and attenuated by the AMPA-selective antagonists, NBQX (1 and 10 μM), LY 293558 (1 and 10 μM) and GYKI 52466 (10 and 30 μM).
3. By use of an experimental procedure with consecutive applications of AMPA (100 μM, 28 min apart), the second response was reduced, indicative of receptor desensitization, and was reversed by cyclothiazide in a concentration-dependent manner (1–300 μM). The concentration-response curve for AMPA-induced release of [³H]-noradrenaline was shifted leftwards, but the reversal by cyclothiazide of the desensitized response was partial and failed to reach the maximal response of the first stimulus.
4. Observations made with various schedules of cyclothiazide application indicated that the initial AMPA-evoked response was already partially desensitized (150% potentiation by 100 μM cyclothiazide) and that the desensitization was not likely to be due to a time-dependent diminution and was long-lasting (second application of cyclothiazide was ineffective).
5. Co-application of a number of drugs with actions on second messenger systems, in association with the second AMPA stimulus, revealed significant potentiation of the AMPA-induced release of [³H]-noradrenaline: forskolin (10 μM, +78%), Rp-cAMPS (100 μM, +65%), Ro 31-8220 (10 μM, + 163%) and thapsigargin (100 μM, +161%).
6. The AMPA receptor-mediated response regulating the release of [³H]-noradrenaline from rat hippocampal slices was desensitized and cyclothiazide acted to reverse partially the desensitization in a concentration-dependent manner. Since the time-course of desensitization was longer lasting than that noted in previous electrophysiological studies, multiple events may be involved in the down-regulation of AMPA receptor activity including receptor phosphorylation and depletion of intracellular Ca²⁺ stores.

     

YM90K, an AMPA receptor antagonist, protects against ischemic damage caused by permanent and transient middle cerebral artery occlusion in rats

The neuroprotective effect of YM90K, a potent AMPA receptor antagonist, was examined in rats with permanent and transient occlusion of middle cerebral artery (MCA) using intraluminal suture occlusion method. In rats with permanent MCA occlusions, two types of occluders were used to compare the efficacy of YM90K. When a 4–0 (diameter: 0.19 mm) suture was used, YM90K (20 mg kg^–1 h^–1 i.v. infusion for 4 h) significantly reduced infarct volume (P<0.05) and neurologic deficits (P<0.05) 24 h after MCA occlusion. Infarct volume was also reduced by YM90K at the same dose (P<0.01) when severe ischemia was induced by a 3–0 (diameter: 0.23 mm) suture. In rats with transient (3 h) MCA occlusions, a 10-mg kg^–1 h^–1 dose of YM90K that did not show significant protection in rats with permanent MCA occlusion offered neuroprotective effects. These data demonstrate that YM90K provides cerebral neuroprotection against a wide range of ischemic insults. Received: 19 June 1998 / Accepted: 2 September 1998     

Studies of the antagonist actions of (RS)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO) on non-NMDA receptors in cultured rat neurones

1. Whole-cell patch-clamp recordings from single cultured cortical neurones have been used to study the action of (RS)-2-amino-3-[5-tert-butyl-3-(phosphonomethoxy)-4-isoxazolyl]propionic acid (ATPO), which has previously been proposed to be a potent selective antagonist of 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptors.
2. ATPO competitively reduced peak responses evoked by semi-rapid applications of AMPA (K_i=16 μM) but had variable effects on plateau responses, which were on average unchanged. Following blockade of AMPA receptor desensitization by cyclothiazide (CTZ, 100 μM), the plateau responses were reduced by ATPO to a similar extent as the peak responses, indicating that ATPO reduces desensitization of AMPA receptors.
3. Semi-rapid application of kainic acid (KA) and the KA receptor-selective agonist, (2S,4R)-4-methylglutamic acid (MeGlu) evoked non-desensitizing responses which were competitively antagonized by ATPO (K_i values: 27 and 23 μM, respectively).
4. Responses to MeGlu were unaffected by CTZ (100 μM), but potentiated 3 fold following blockade of KA receptor desensitization by concanavalin A (Con A, 300 μg ml⁻¹). Responses of spinal cord neurones to MeGlu were blocked by ATPO to a similar extent before and after blockade of KA receptor desensitization by Con A.
5. Although selectively potentiated by Con A, plateau responses to MeGlu were reduced by 69.6% by the AMPA selective antagonist, GYKI 53655 (10 μM). The remaining component was further reduced by ATPO with a K_i of 36 μM, which was not significantly different from that in the absence of GYKI 53655, but was greater than that on responses to AMPA.
6. It is concluded that ATPO is a moderate-potency competitive inhibitor of naturally expressed non-NMDA receptors.

     

Differential regulation of glutamate receptor-mediated BDNF mRNA expression in the cerebellum and its defects in stargazer mice

Activity-dependent regulation of BDNF expression plays important roles in synaptic plasticity and neuronal function. We have investigated glutamate receptor-mediated regulation of BDNF expression in the cerebellum of wild-type and stargazer (stg) mice. Both in vivo and in vitro studies revealed that BDNF response kinetics in the cerebellum were much delayed with reversed sensitivity to NMDA versus non-NMDA agonist exposures significantly different from those in the cortex and hippocampus of wild-type mice. In stg mice, the severely impaired BDNF expression was restricted to the cerebellum while responses in the forebrain were intact. A selective failure of BDNF mRNA response to AMPA stimulation, but not NMDA, was evident in cultured stg cerebellar granule cells. These results demonstrate that BDNF expression is differentially regulated with region-specific kinetics. It indicates that the BDNF expression defect in the stg cerebellum is attributable to the AMPA receptor defect caused by the stargazin mutation.