钩藤碱对苯丙胺依赖大鼠神经核团中NR2B mRNA表达的影响

目的研究钩藤碱对苯丙胺诱导的条件性位置偏爱大鼠伏核和杏仁核中NR2B mRNA表达的影响。方法将56只♂SPF级SD大鼠分为正常对照组、苯丙胺模型组、氯胺酮+苯丙胺组、钩藤碱低、中、高剂量+苯丙胺组和钩藤碱+生理盐水组,每组8只。按要求分别给予相应药物。d5用条件性位置偏爱箱观察大鼠在白箱中的停留时间,并用原位杂交技术对伏核和杏仁核NR2B mRNA表达进行检测。结果①连续4d给予苯丙胺2mg.kg-1建立了位置偏爱模型,氯胺酮及钩藤碱低、中、高剂量均可消除位置偏爱效应,随钩藤碱剂量增加效应加强,且钩藤碱自身无精神依赖性;②苯丙胺模型大鼠伏核和杏仁核NR2B mRNA表达较正常对照大鼠明显增加,氯胺酮及中、高剂量钩藤碱抑制NR2B mRNA的表达,低剂量无明显影响。钩藤碱本身不影响正常大鼠NR2B mRNA的表达。结论伏核和杏仁核NR2B mRNA的表达参与了钩藤碱抗苯丙胺依赖作用的分子生物学机制。     

Intrathecal administration of roscovitine inhibits Cdk5 activity and attenuates formalin-induced nociceptive response in rats

Aim: To investigate effects of the cyclin-dependent kinase5 (Cdk5) inhibitor roscovitine on formalin-induced nociceptive responses in rats. Methods: The flinch response as a methood of pain threshold measurement and intrathecal injection techniques were used. Cdk5 and phosphorylation of its downstream target,DARPP-32 (dopamine-and cAMP-regulated phosphoprotein of Mr32 kDa), were investigated by Western blot analysis. Results: Rats demonstrated a typical flinch response after formalin injection. Intrathecal roscovitine injections significantly suppressed the flinch response in a dose-dependent manner. Western blot analysis showed that phosphorylated DARPP-32 at Thr75 increased in concentration after formalin hyperalgesia, with this effect reduced by roscovitine administration. This antinociception was partially attenuated by administration of naloxone before the formalin test. Conclusion: DARPP-32 phosphorylation is in volved inacute inflammatory pain response. Intrathecal roscovitine administration attenuates formalin-induced nociceptive responses and there is potential for further application.     

NMDA受体NR2B亚单位在慢性内脏痛觉敏化中的作用

目的探讨外周与脊髓NMDA受体NR2B亚单位在慢性内脏痛觉敏化中的作用。方法模型组大鼠出生后d8～15,每天接受一次伤害性结直肠扩张刺激,8wk龄后用腹壁撤退反射(AWR)评估大鼠肠道敏感性。对腰骶背根神经节及胸腰与腰骶脊髓背角神经元进行免疫组织化学染色,比较对照与模型大鼠NR2B的表达。并比较对照与模型两组大鼠腹腔注射AP-7(NMDA受体拮抗剂)前后原发传入神经对结直肠扩张刺激的反应。结果①模型组大鼠AWR评分显著增高。②模型大鼠脊髓背根神经节NR2B亚单位表达增强。③模型大鼠脊髓内脏相关神经元NR2B亚单位表达增强。④AP-7显著抑制模型大鼠腰骶传入神经纤维对结直肠刺激的反应。结论NMDA受体NR2B亚单位可能参与慢性内脏痛外周与脊髓痛觉敏化的过程。     

Isoflurane anaesthesia reversibly improves cognitive function and long-term potentiation (LTP) via an up-regulation in NMDA receptor 2B subunit expression

Postoperative cognitive dysfunction (POCD) is a decline in cognitive performance after a surgery performed under anaesthesia. The exact roles of surgery and/or anaesthesia for facilitating POCD are unclear. This study investigates the effects of isoflurane anaesthesia on cognitive performance and cellular mechanisms involved in learning and memory function. Male C57BL6/J mice (age: 4-5 months) were anaesthetized with isoflurane in oxygen/air (FiO₂ = 0.5) for 2 h, non-anaesthetized mice served as controls. After 24 h, neurocognitive function, in vitro long-term potentiation (LTP), or protein expression were evaluated. In a visuospatial test, anaesthetized mice showed better cognitive performance as they learned faster compared to controls. In hippocampal slices of anaesthetized mice, in vitro LTP was enhanced as reflected in an increased extracellular field potential (fEPSP) slope after 1 h to 210.2 ± 17% (control: 156.8 ± 7.2%; n = 14; p < 0.05). NR2B subunits of the NMDA receptors were selectively up-regulated in hippocampal neurones after anaesthesia. Blocking these receptors either with the NR2B selective antagonists ifenprodil or RO25-6981 (R-(R,S)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperidine propranol), prevents the anaesthesia-induced improvement in cognitive function as well as enhancement of in vitro LTP. The anaesthesia-mediated effects on NR2B subunits were fully reversed to control levels seven days after anaesthesia. The present data suggests that isoflurane anaesthesia induces a hippocampus-specific elevation of NR2B subunit composition, enhances LTP in CA1 neurones, and produces hippocampal-dependent cognitive improvement.     

三七总皂苷对脑出血大鼠前脑兴奋性氨基酸受体NR2A和NR2B表达的作用

N-甲基-D-天门冬氨酸受体（NMDA受体）是由NRI和NR2（NR2A～NR2D）亚单位构成的功能性异聚体，其中NR2参与NMDA受体的组成并修饰其功能。许多研究表明，NMDA受体介导的Glu神经兴奋毒性作用在缺血性脑损伤的众多环节中起着关键作用。本实验主要研究三七总皂苷对脑出血大鼠前脑病灶周围NR2A、NR2B表达的作用。     

选择性N-甲基-D-天门冬氨酸受体NR2B亚型阻滞剂的研究进展

选择性N-甲基-D-天门冬氨酸受体NR2B亚型阻滞剂近年来受到了越来越多的关注。目前，已报道的NR2B亚型阻滞剂的结构类型绝大多数仍为艾芬地尔发展而来的哌啶衍生物，另外还有酰胺、脒、氨基喹啉等结构类型；NR2B亚型阻滞剂在神经元保护、镇痛、抗药物依赖、抗帕金森病等方面表现了潜力。现根据不同结构类型综述NR2B亚型阻滞剂的结构及药理活性，并探讨其毒副作用较低的可能原因和临床应用潜力。     

Regulation of NMDA receptor subunit expression and its implications for LTD, LTP, and metaplasticity

NMDA-type glutamate receptors (NMDARs) mediate many forms of synaptic plasticity. These tetrameric receptors consist of two obligatory NR1 subunits and two regulatory subunits, usually a combination of NR2A and NR2B. In the neonatal neocortex NR2B-containing NMDARs predominate, and sensory experience facilitates a developmental switch in which NR2A levels increase relative to NR2B. In this review, we clarify the roles of NR2 subunits in synaptic plasticity, and argue that a primary role of this shift is to control the threshold, rather than determining the direction, for modifying synaptic strength. We also discuss recent studies that illuminate the mechanisms regulating NR2 subunits, and suggest that the NR2A/NR2B ratio is regulated by multiple means, which may control the ratio both locally at individual synapses and globally in a cell-wide manner. Finally, we use the visual cortex as a model system to illustrate how activity-dependent modifications in the NR2A/NR2B ratio may contribute to the development of cortical functions.     

NR2B containing NMDA receptor dependent windup of single spinal neurons

Windup, the frequency dependent build-up of spinal neuronal responses, is implicated in the development of central sensitization of nociceptive pathways. N-methyl-D-aspartate (NMDA) receptors have been shown to be involved in these processes but the role of various receptor subtypes at the spinal level is not fully understood. In our experiments, we compared the inhibitory effect of MK-801 (a nonselective NMDA receptor antagonist, 0.01-3 mg/kg i.v.) and CI-1041 (an NR2B subunit specific NMDA receptor antagonist, 0.3-10 mg/kg i.v.) on the formation of dorsal horn neuronal windup in spinalized rats, in vivo. Both types of antagonist blocked windup considerably at doses not affecting the normal synaptic transmission. These results are in agreement with the well-documented effectivity of NR2B subtype selective NMDA receptor antagonists in chronic pain models and give the first direct evidence that spinal mechanisms are involved in this effect.     

Nucleus accumbens NMDA receptor subunit expression and function is enhanced in morphine-dependent rats

We have previously shown, using radioligand binding studies, that N-methyl-d-aspartate (NMDA) NR1 and NR2A receptor subunits density was decreased in the forebrain of morphine-dependent rats. We have now determined if morphine-dependent rats display regional differences in NMDA receptor expression and whether such changes are functionally relevant. In morphine-dependent rats, the expression of NR1 and NR2A subunits protein, as determined by Western blotting with NMDA receptor subunit antibodies, were decreased in frontal cortex and hippocampus but significantly increased in the nucleus accumbens. The expression of the NR2B subunit was unchanged in all regions examined. In separate groups of morphine-dependent rats, MK-801-induced hyperactivity (thought to be mediated via modulation of nucleus accumbens dopamine release) was significantly enhanced in morphine-dependent animals. Similarly, the MK-801-induced increase of dopamine metabolism was significantly increased in the nucleus accumbens of morphine-dependent animals as compared to sham controls. Results provide both biochemical and behavioural evidence to suggest that NMDA receptor function in the nucleus accumbens, at least with respect to an interaction with the limbic dopamine system, is markedly enhanced in morphine-dependent rats. This increase in function may be associated with an enhanced expression of NMDA receptors, particularly those in the nucleus accumbens containing the NR2A subunit. Taken together, these data support several studies in the literature indicating that NMDA receptors in the nucleus accumbens are involved in the process of opiate dependence.     

急性阿片耐受大鼠脊髓NMDA受体NR2A及NR2B亚基表达的改变

目的：了解大鼠短期多次应用芬太尼能否发生急性阿片耐受以及急性阿片耐受大鼠脊髓NMDA受体NR2A和NR2B亚基表达的改变。方法：24只体重为200-220g的雄性SD大鼠随机分为3组（n=8）：对照组（C）,生理盐水组（S）及芬太尼组（F）。F组大鼠给予皮下注射芬太尼30μg/kg,共4次,每两次注射之间间隔15min,S组大鼠以生理盐水代替芬太尼,C组大鼠未给药。给药前及给药结束后每30min以Von-Frey仪测定各组大鼠的机械刺激缩足阈值（paw withdrawal threshold,PWT）。当F组大鼠的PWT恢复到给药前基础水平时,各组大鼠均给予腹腔注射吗啡5mg/kg。随后仍每30min测定各组大鼠的PWT,直至F组大鼠的PWT再次回到基础水平。对各组大鼠不同时间点的PWT进行组内和组间比较。另24只体重为2000-220g的雄性SD大鼠分组及给药方法同前（分为C^＊、S^＊及F^＊组）,当F＊组大鼠的PWT首次恢复到基础值时,不给予吗啡,处死各组大鼠,取脊髓,以Western blotting方法测定NMDA受体NR2A及NR2B亚基的蛋白表达水平。结果：连续4次皮下注射芬太尼（F组）后大鼠首先表现为PWT较基础值显著升高,随后PWT降低到基础值以下,然后逐渐恢复至基础值水平,此时皮下注射吗啡后,吗啡的镇痛效果显著低于其他两组大鼠（S组,C组）。F^＊组大鼠脊髓的NR2B亚基表达水平显著高于C^＊组及S^＊组,各组大鼠脊髓的NR2A亚基表达水平的差异无统计学意义。结论：短期应用芬太尼可导致大鼠发生急性阿片耐受。急性阿片耐受大鼠的脊髓NMDA受体NR2B亚基表达水平显著升高,NR2A亚基表达水平无明显变化。     

Conditioning-strength dependent involvement of NMDA NR2B subtype receptor in the basolateral nucleus of amygdala in acquisition of auditory fear memory

It is known that N-methyl-D-aspartate (NMDA) receptor in the basolateral nucleus of amygdala (BLA) is essential for fear memory formation. NMDA NR2B and NR2A subtype receptors exhibit difference in electrophysiological and signaling properties. However, it is unclear whether these two subtype receptors have different roles in fear memory formation. Here, we provide evidence, using pharmacological blockade and genetic interference, that NR2B is involved in acquisition of auditory fear memory in a conditioning-strength dependent way. Pre-conditioning intra-BLA infusion of the NR2B selective antagonist ifenprodil or Ro25-6981 impaired 48-h auditory fear memory (AFM) induced by five but not one CS-US pairing protocol, while similar treatment with the NR2A antagonist NVP-AAM077 disrupted memory for both protocols. Consistently, genetic over-expression of NR2B C-terminal in the BLA, which interferes with the C-terminal mediated intracellular signaling, produced a severe deficit in 48-h AFM for five but not one CS-US pairing protocol, whereas over-expression of NR2A C-terminal impaired memory for both protocols. Furthermore, pre-conditioning infusion of ifenprodil down-regulated the elevated phosphorylation level of extracellular signal-regulated kinase (ERK) induced by five CS-US pairing protocol. Thus, the involvement of BLA NR2B in AFM acquisition depends on conditioning strength.     

NMDA receptor antagonists as analgesics: focus on the NR2B subtype

Ifenprodil and a group of related compounds are selective antagonists of NR2B-containing NMDA receptors. These compounds are antinociceptive in a variety of preclinical pain models and have a much lower side-effect profile compared with other NMDA receptor antagonists. It remains unclear whether the improved safety of these compounds is due to their subtype selectivity or to a unique mode of inhibition of the receptor. Human trials have so far confirmed the good tolerability of these subtype-selective NMDA receptor antagonists; however, whether they are as effective as other NMDA receptor antagonists in pain patients remains to be demonstrated.     

Ethanol-related behaviors in mice lacking the NMDA receptor NR2A subunit

Rationale The ionotropic NMDA glutamate receptor is composed of NR1 and NR2 (NR2A-D) subunits. While there is compelling evidence that NMDA receptors modulate behavioral effects of ethanol, there is little understanding of how the subunit composition of the NMDA receptor mediates these effects.Objectives In the current study, we assessed the relative roles of NMDA subunits via phenotypic assessment of ethanol-related behaviors in NR2A knockout (KO) mice.Results Results demonstrated that NR2A KO and heterozygous mice failed to show evidence of ethanol-induced conditioned place preference. As compared to wild-type (WT) controls, KO mice showed impaired motor coordination at baseline and, in some instances, following ethanol treatment on the accelerating rotarod, balance beam, and wire-hang tests. By contrast, open field locomotor-stimulant, sedative/hypnotic, and hypothermic responses to ethanol were not different between genotypes, nor was voluntary ethanol consumption and preference in a two-bottle choice paradigm. Blood ethanol concentrations were lower in KO than WT mice following intraperitoneal ethanol injection.Conclusions Results suggest that the loss of NR2A subunit-containing NMDA receptors impairs the ability to form or express learned reward-related responses to ethanol and causes deficits in motor coordination. However, the loss of NR2A does not alter other measures of acute ethanol intoxication or ethanol consumption, possibly implicating other NMDA subunits in these effects. These data provide novel insight into the role of NMDA receptors in modulating the behavioral effects of ethanol.Research supported by the National Institute on Alcohol Abuse and Alcoholism Intramural Research Program.     

选择性NMDA受体NR2B亚单位拮抗剂与神经元保护作用

多种神经系统疾病与谷氨酸过度兴奋NMDA受体有关。广谱的NMDA受体拮抗剂能影响所有NMDA受体而产生不良反应，限制了其临床运用。NMDA受体NR2B亚单位在神经系统疾病中起着重要的作用，艾芬地尔等化合物能够选择性地作用于NMDA受体NR2B亚单位，将有可能发展成为临床上安全、有效的神经元保护剂。     

Neonatal toluene exposure alters agonist and antagonist sensitivity and NR2B subunit expression of NMDA receptors in cultured cerebellar granule neurons.

Toluene has been reported to antagonize the function of N-methyl-D-aspartate (NMDA) receptors. In this study, the effects of neonatal toluene exposure on NMDA receptors in primarily cultured cerebellar granule neurons were examined. Sprague-Dawley rats were treated with toluene (0, 200, 500, and 1000 mg/kg, i.p.) from postnatal day (PN) 4 to PN 7. Under toluene-free conditions, Ca2+ signals of cultured neurons in response to glutamate and NMDA were measured for up to 14 days. The expression of NMDA receptor subunits (NR1, NR2A, and NR2B) at 5-14 days in vitro (DIV) were also determined. Neonatal toluene exposure dose-dependently reduced intracellular Ca2+ signals in response to glutamate/glycine and NMDA/glycine in cultured cerebellar granule neurons, and these effects were gradually decreased with time. Such toluene exposure did not influence the inhibition of Mg2+ or MK801 on NMDA-evoked responses, but it decreased the potency of ifenprodil (an NR2B preferring antagonist). The protein levels of NMDA receptor subunit NR2B were consistently reduced by toluene exposure at 5 DIV, but not at 14 DIV. These results demonstrate that neonatal toluene exposure induces long-term but reversible changes in the function and composition of NMDA receptors. Such changes during developmental stages may contribute to the cerebellar dysfunction observed in fetal solvent syndrome.     

Development of a selective competitive receptor binding assay for the determination of the affinity to NR2B containing NMDA receptors

A selective, rapid and efficient competitive binding assay for the determination of the affinity of compounds towards the ifenprodil binding site of NR2B subunit containing NMDA receptors has been developed. In the assay system, [³H]ifenprodil was used as radioligand and membrane homogenates from L(tk-) cells stably expressing recombinant human NR1a/NR2B receptors served as the receptor material. Sonication of the cells during work-up, performing all steps with 96-well multiplates and using a solid scintillator represent particular features of this assay. The binding kinetics was investigated by saturation and association/dissociation experiments. [³H]ifenprodil bound to a single, saturable site on human recombinant NR1a/NR2B receptors, resulting in a B_max-value of 25.8 pmol/μg protein and K_d-value of 7.6 ± 2.3 nM (SEM). The dissociation rate constant (k_off) was 0.03861 min⁻¹ and the association rate constant k_on resulted in 0.00625 nM⁻¹ min⁻¹. The specificity of the assay was proved with cells not treated with dexamethasone, which has to be added to induce NMDA receptor synthesis of the cells. Additionally, the absence of α₁, σ₁ and σ₂ receptors was shown. The K_i-values of the NR2B ligands ifenprodil and eliprodil determined with the new assay are in good accordance with reported data.     

Differential roles of NR2A and NR2B subtypes in NMDA receptor-dependent protein synthesis in dendrites

Protein synthesis in dendrites is critical for long-term synaptic plasticity. Previous studies have identified an essential role of NMDA receptors in control of activity-dependent dendritic protein synthesis, but the contribution of NR2A- and NR2B-containing NMDA receptors, the two predominant subtypes of NMDA receptors in the forebrain, has not been determined. Using a pharmacological approach, we investigated the role of NR2A and NR2B subtypes in the regulation of NMDA-induced dendritic translation of a GFP reporter mRNA controlled by CaMKII untranslated regions (UTRs). We found that ifenprodil and Ro25-6981, two specific inhibitors of NR2B-containing NMDA receptors, did not affect dendritic GFP synthesis induced by NMDA. In contrast, NVP-AAM077, an antagonist that preferentially blocks the NR2A subtype, completely abolished NMDA-induced GFP synthesis in dendrites. Our results together suggest that NR2A but not NR2B subtypes are indispensable for NMDA receptor-dependent dendritic protein synthesis.     

脱氢表雄酮对大鼠大脑皮质神经元氨基酸受体亚单位NR2B和GBR1表达的影响

目的研究脱氢表雄酮(DHEA)对大鼠大脑皮质神经元氨基酸受体亚单位NR2B和GBR1表达的影响。方法不同剂量(1、10、100μmol.L-1)的DHEA处理原代培养的大鼠大脑皮质神经元,采用免疫细胞化学法测定神经元氨基酸受体亚单位NR2B和GBR1表达的变化。结果与对照组相比,低、中、高剂量DHEA使NR2B表达分别增加15.6%、19.9%、49.4%(P<0.05或P<0.01);使GBR1表达分别增加4.3%(P>0.05)、14.5%、58.5%(P<0.05或P<0.01)。结论DHEA可增强氨基酸受体亚单位NR2B和GBR1的表达水平。     

姜黄素对缺血/再灌注大鼠海马神经细胞凋亡及NR2A、NR2B表达的影响

目的观察不同剂量姜黄素对大鼠全脑缺血/再灌注后海马神经细胞凋亡及N-甲基-D-天门冬氨酸受体亚单位NR2A、NR2B表达的影响。方法采用SD大鼠四血管阻断模型,动物随机分为5组:假手术组(SH组)、缺血/再灌注组(I/R组)、姜黄素30、100、300mg·kg-1组(Cur30、100、300组),每组根据再灌注不同时间点(2h、6h、1d、3d、7d)又分5个亚组。HE染色观察海马神经细胞形态;TUNEL法检测海马CA1区神经细胞凋亡;免疫组化检测NR2A、NR2B蛋白在海马CA1区及CA3/DG区的表达。结果I/R组凋亡细胞多于SH组及Cur100组,Cur300组凋亡细胞多于Cur100组。姜黄素处理各组及SH组各时间点CA1区、CA3/DG区NR2A的表达均高于I/R组(P<0.05)。SH组及Cur100组CA1、CA3/DG区各时间点NR2B表达低于I/R组(P<0.05)。结论姜黄素减少缺血性神经细胞凋亡的发生可能与增加NR2A、降低NR2B蛋白表达有关;100mg·kg-1姜黄素抗凋亡作用最佳。     

糖尿病神经痛大鼠脊髓背角NMDA受体表达的变化

目的探讨糖尿病神经病理性痛(DNP)大鼠脊髓背角N-甲基-D-天冬氨酸(NMDA)受体表达的变化。方法 SD雄性大鼠24只,4周龄,体重130～150g,随机分为2组,DNP组(D组,n=15)腹腔注射链尿佐菌素(STZ)50mg/kg制备成DNP模型,正常对照组(C组,n=9)给予等容量0.9%氯化钠溶液。给予STZ或0.9%氯化钠溶液后3、5、7周时分别取D组(5只)和C组(3只)大鼠,测量体重,采集静脉血样,测定空腹血糖浓度,然后测定机械缩足阈值,取脊髓组织,采用免疫组织化学法分别测定脊髓背角NR1和NR2B亚单位表达水平。结果与C组比较,在各时间点,D组体重下降,血糖升高,机械缩足阈值明显降低(P<0.05),脊髓背角NR1和NR2B亚单位免疫阳性细胞数表达明显增加(P<0.05)。结论脊髓背角NMDA受体在脊髓水平参与了大鼠糖尿病神经病理性痛的形成。