帕金森病模型大鼠海马mGluR5的表达变化及意义

目的探讨帕金森病(PD)模型大鼠海马mGluR5的表达变化及意义。方法将SD大鼠随机分为正常对照组(A组)、PD模型组(B组)和非竞争性NMDA受体拮抗剂D-AP-5+PD组(C组),通过免疫组织化学方法观察多克隆抗体mGluR5在大鼠海马的表达变化。结果正常对照组中大鼠海马有丰富的mGluR5表达;PD模型组中大鼠海马mGluR5表达明显下降;在非竞争性NMDA受体拮抗剂D-AP-5+PD组中,大鼠海马mGluR5表达又明显上调。结论帕金森病模型大鼠海马各区mGluR5表达下降,可能是神经细胞的一种自我保护作用。mGluR5可能与帕金森病认知和情感及记忆功能障碍有关。帕金森病模型大鼠海马各区经用非竞争性NMDA受体拮抗剂D-AP-5处理后,海马mGluR5表达明显上调,推测mGluR5表达下降可能在帕金森病长时程增强(LTP)诱导过程中具有重要作用,其作用机制可能为NMDA受体依赖性。     

糖尿病大鼠胃肠动力及肌间神经丛形态学改变

目的 了解糖尿病大鼠胃肠动力障碍时，肌间神经丛有无形态学异常并探讨胃肠功能异常的机制。方法 30只大鼠分成对照组（10只）和糖尿病组（20只），糖尿病组用链脲佐菌素建立大鼠糖尿病模型，4个月后测定两组大鼠胃肠传输速率，并用酶组织化学方法观察回肠肌间神经丛内胆碱能和氮能神经的组织学改变。结果 糖尿病组大鼠胃肠传输速率明显延迟，回肠肌间神经丛内胆碱能神经元密度明显降低（P〈0．01），氮能神经节和氮能神经元的密度均显著升高（P〈0．05和P〈0．01）。结论 糖尿病大鼠小肠肌间神经丛内胆碱能神经减少，氮能神经增多，这可能是导致胃肠传输速率延迟的重要原因，由此引起小肠运动障碍。     

慢传输型便秘患者结肠中五羟色胺受体亚型的表达及意义

目的:研究主要5-HT受体亚型在慢传输型便秘(slowtransitconstipation,STC)患者结肠中的表达,探讨其在慢传输型便秘发病机制中的作用.方法:采用免疫组化EnVision法,检测20例STC患者和20例对照组结肠组织中5-HT1A,5-HT3和5-HT4受体的分布及表达水平,并采用IMS计算机辅助图像分析系统进行半定量分析.结果:5-H1A受体分布于黏膜下层、肌层,肌间神经丛5-HT1A受体的表达在STC组和对照组间无显著差异(P=0.548).5-HT3受体分布于黏膜下层和肌层,肌间神经丛STC组阳性指数显著低于对照组(65.2±15.9vs94.3±20.1,P<0.01).5-HT4受体分布于黏膜层、黏膜下层、肌层.在黏膜层和肌间神经丛,STC组5-HT4受体阳性指数均显著低于对照组(57.8±10.9vs78.5±12.9,P<0.01;77.5±19.9,119.2±26.9,P<0.01).STC组中,5-HT3受体表达水平与结肠传输试验第5天体内残留标志物数量无关(P>0.05);但5-HT4受体表达水平与第5天体内残留标志物数量呈负相关(r=-0.782,P<0.01).结论:STC患者结肠中存在5-HT3和5-HT4受体亚型的表达下调,两者可能参与了STC的发病机制.     

代谢型谷氨酸受体在大鼠糖尿病神经病理性疼痛中的作用

目的评价代谢型谷氨酸受体(mGluR5)在大鼠糖尿病神经病理性疼痛中的作用。方法 3月龄Wistar大鼠,雌雄不限,体重180～220g,单次腹腔注射链脲佐菌素(STZ)65mg/kg制备糖尿病大鼠神经病理性疼痛模型。模型制备成功大鼠64只,随机分为2组(n=32),糖尿病神经病理性疼痛组(D组)和mGluR5拮抗剂组(M组),另取32只正常大鼠作为对照组(C组,n=32)。M组腹腔注射mGluR5拮抗剂20mg/kg,1次/d,C、D组注射等体积生理盐水。各组分别于第2、4、6、8周(T1～4)末随机取8只大鼠,采用vonFrey纤维丝测定双后足机械缩足反应阈值(MWT),取L3～6脊髓,采用免疫组化法和RT-PCR法检测mGluR5的mRNA水平。结果与C组比较,D组T1～4时MWT降低,mGluR5mRNA水平升高(P0.05);与D组比较,M组T1～4时MWT升高mGluR5mRNA水平下降(P0.05)。结论 mGluR5激活参与大鼠糖尿病神经病理性疼痛的形成。     

mGluR1蛋白诱导海马组织自噬对脑血管痉挛小鼠学习记忆能力的影响

目的探讨小鼠脑血管痉挛(CVS)后代谢型谷氨酸受体1(mGluR1)对神经细胞自噬的影响。方法采用非开颅血管内穿线法制备小鼠CVS模型,随机分为假手术组、模型组、mGluR1拮抗剂LY367385组,于术后10 min侧脑室注射生理盐水或LY367385(500 nmol)5μl,采用Y型电迷宫检测小鼠自主活动及学习记忆能力。分别于SAH术后6、24、48 h 3个时相点取脑组织标本,HE染色观察右侧海马CA1区组织学变化,免疫印迹法检测mGluR1、Beclin-1蛋白表达。结果与对照组比较,模型组小鼠神经功能评分显著降低,随痉挛时间延长,各组小鼠mGluR1、Beclin-1蛋白均有不同程度增强(P<0.05)。与模型组比较,拮抗剂组mGluR1、Beclin-1蛋白表达均有不同程度下调(P<0.05),并且神经功能评分得到改善。结论脑血管痉挛后mGluR1表达增强可通过激活Beclin-1途径诱导小鼠海马区神经细胞自噬。     

肠道嗜铬细胞数量和5-羟色胺受体3表达在大鼠衰老过程中的变化及意义

目的 检测不同鼠龄SD大鼠肠道推进率、肠道黏膜嗜铬细胞数量和肠肌间神经丛5-羟色胺受体3(5-HT3R)的表达,探讨生理性衰老过程中肠道运动功能变化的规律及其机制. 方法 80只健康SD大鼠分为3月龄、9月龄、18月龄、24月龄及30月龄5组,每组各16只.以印度墨汁为标记物,检测大鼠的肠道推进率;采用免疫组化链霉亲和素-生物素-过氧化物酶复合物(SABC)法染色,检测大鼠空肠、回肠和结肠黏膜及黏膜下嗜铬细胞的数量以及肠肌间神经丛5-HT3R的表达.结果肠道推进率30月龄组大鼠为(52.1±9.8)%,明显低于3月龄组(67.2±13.5)%(t=7.013,P=0.001);30月龄组大鼠空肠、回肠及结肠黏膜和黏膜下嗜铬细胞数量分别为(11.1±3.0)个、(10.6±1.9)个和(10.2±4.3)个,较3月龄组(22.9±6.2)个、(25.8±7.1)个和(23.0±5.7)个减少(t=3.640,t=3.384,t=4.154,均为P<0.01);大鼠空肠和结肠的5-HT3R表达30月龄组分别为4.8±1.4和9.3±4.2,较9月龄组的8.9±1.5和14.5±5.3减少(t=3.464,t=3.003,均为P<0.01),回肠5-HT3R 30月龄组和3月龄组分别为5.0±1.3和9.0±1.7(t=4.549,P<0.001). 结论 老年大鼠肠道推进率、肠道嗜铬细胞数量及肠肌间神经丛5-HT3R表达均显著降低,并随年龄增长而逐渐明显;老年大鼠肠道运动功能的明显下降与肠嗜铬细胞数量以及肌间神经丛5-HT3R的表达显著降低有一定的相关性.     

mGluRs与帕金森病相关研究进展

<正>帕金森病(PD)是常见的神经退行性疾病,其症状除了常见的运动障碍,还有情感认知障碍。运动障碍与多巴胺(DA)能神经元的渐进性丧失、DA减少有关。兴奋性和抑制传输情感和认知障碍与谷氨酸代谢有关。在基底神经节(BG)区,DA和谷氨酸相互作用,共同调节运动和认知行为。谷氨酸通过谷氨酸受体(GluRs)发挥作用,该受体分为离子型受体和代谢型受体(m GluRs)。研究表明,Ⅰ型m GluRs的拮抗剂和Ⅱ型、Ⅲ     

糖尿病30周大鼠胃肌间丛神经元尼氏体的变化

目的 检测糖尿病大鼠胃肌间丛神经元尼氏体的变化.方法 应用链脲佐菌素建立SD大鼠糖尿病模型,成模30周后,采用甲苯胺蓝染色法检测糖尿病30周大鼠、中药治疗组及正常对照组的胃肌间丛神经元尼氏体.结果 糖尿病30周大鼠胃肌间丛神经元尼氏体数量少于正常对照组(P＜0.01);而中药治疗组数量较多,与正常对照组无统计学差异.结论 糖尿病30周大鼠胃肌间丛神经元尼氏体数量减少,显示神经损害;中药治疗组尼氏体数量较多,显示中药的保护作用.     

Ghrelin在大鼠神经系统中的表达对胃黏膜的保护作用

目的:研究大鼠脑、小肠肌间神经丛神经元和血浆内Ghrelin的表达,探讨Ghrelin在水浸加束缚应激性胃溃疡中的作用及机制．方法:选择健康♂Wiater大鼠76只,随机分为 6组:水浸加束缚组(10只);侧脑室注射Ghrelin 组(24只);皮下注射L-NAME 侧脑室注射 Ghrelin组(8只)和相应的3个对照组(正常大鼠组18只,侧脑室注射生理盐水组8只,皮下注射 L-NAME 侧脑室注射生理盐水组8只)．采用放射免疫分析、荧光免疫组化双染和神经生理学等实验方法,观察脑、小肠肌间神经丛和血浆内Ghrelin的表达,探讨Ghrelin对大鼠束缚加水浸诱导的应激性胃溃疡的影响及机制．结果:在正常大鼠小肠肌间神经丛内和原代培养的肠肌间神经丛神经元均可见有Ghrelin 样免疫反应阳性物(Ghrelin-IR)的表达,且 Ghrelin-IR与胆碱乙酰转移酶(CHAT)共同表达于同一神经元内,但Ghrelin-IR不与一氧化碳合酶(NOS)和消化道感觉性神经元内特有的钙结合蛋白(Calbindin,Calb)共存．在大鼠应激性胃溃疡产生的同时,其血浆内Ghrelin- IR的含量明显减少(198．3±29．6 ng/L vs 141．7 ±26．5 ng／L．P=0．026)．而下丘脑、延脑、垂体和肌间神经丛神经元内Ghrelin-IR的含量明显升高(分别为96．2±18．1 pg／mg vs 153．2 ±11．6 pg／mg．P=0．006;89．8±16．5 pg／mg vs 144．4±13．9 pg／mg,P=0．007;108．3± 11．9 pg／mg vs 198．2±23．3 pg／mg,P=0．002; 48．8±12．8 pg／mg vs 86．2±21．5 pg／mg．P= 0．02);侧脑室注射Ghrelin大鼠应激性胃溃疡的产生明显减少,且呈明显的量效依赖关系(溃疡指数:生理盐水,86．7±6．2;50 ng Ghrelin,79．3±10．7 P=2．18;500 ng Ghrelin, 61．3±11．7,P=0．04;5 000 ng Ghrelin,35．6 ±10．8,P=0．005),经sc一氧化氮合酶抑制剂 L-NAME后,Ghrelin的胃黏膜细胞保护作用消失．结论:Ghrelin与ChAT共存表达于肠肌间神经丛胆碱能神经元;应激性胃溃疡发生时,中枢神经系统和血浆内Ghrelin的表达发生变化; 中枢Ghrelin对胃黏膜细胞具有保护作用,且呈明显的量效依赖关系．     

肝衰竭大鼠胃窦胆碱能和氮能神经分布的变化分析

目的观察肝衰竭大鼠胃排空及胃窦肌间神经丛胆碱能和氮能神经的变化。方法 40只Wistar大鼠随机分为肝衰竭模型组和对照组,采用葡聚糖蓝-2000为标志物观察大鼠胃排空的变化,应用乙酰胆碱酯酶(AchE)和还原型辅酶Ⅱ硫辛酰胺脱氢酶(NADPH-d)组织化学染色及肌间神经丛全层铺片技术,观察肝衰竭大鼠胃窦肌间神经丛胆碱能和氮能神经的变化,并进行定量分析。计量资料以均数±标准差(x±s)表示,组间比较采用t检验。结果肝衰竭组大鼠胃排空明显减弱(163.00±25.68 vs 100.00±18.93,P0.01),胃窦肌间神经丛胆碱能阳性神经元数量减少,神经纤维变细,分布较稀疏,明显低于对照组(t=3.201,P0.01);氮能神经阳性神经元数量及神经纤维分布明显高于对照组(t=2.912,P0.01)。结论肝衰竭大鼠胃功能的减退与胃窦肌间神经丛胆碱能神经分布减少及氮能神经分布增加有关。     

mGluR5 stimulates gliotransmission in the nucleus accumbens

Although metabotropic glutamate receptor 5 (mGluR5) is essential for cocaine self-administration and drug-seeking behavior, there is limited knowledge of the cellular actions of this receptor in the nucleus accumbens (NAc). Although mGluR5 has the potential to regulate neurons directly, recent studies have shown the importance of mGluR5 in regulating Ca(2+) signaling in astrocytes and, as a consequence, the Ca(2+)-dependent release of excitatory transmitters from these glia. In this study, we demonstrate that activation of mGluR5 induces Ca(2+) oscillations in NAc astrocytes with the correlated appearance of NMDA receptor-dependent slow inward currents detected in medium spiny neurons (MSNs). Photolysis of caged Ca(2+) loaded specifically into astrocytes evoked slow inward currents demonstrating that Ca(2+) elevations in astrocytes are responsible for these excitatory events. Pharmacological evaluation of these glial-evoked NMDA currents shows that they are mediated by NR2B-containing NMDA receptors, whereas synaptic NMDA receptors rely on NR2A-containing receptors. Stimulation of glutamatergic afferents activates mGluR5-dependent astrocytic Ca(2+) oscillations and gliotransmission that is sustained for minutes beyond the initial stimulus. Because gliotransmission is mediated by NMDA receptors, depolarized membrane potentials exhibited during up-states augment excitation provided by gliotransmission, which drives bursts of MSN action potentials. Because the predominant mGluR5-dependent action of glutamatergic afferents is to cause the sustained activation of astrocytes, which in turn excite MSNs through extrasynaptic NMDA receptors, our results raise the potential for gliotransmission being involved in prolonged mGluR5-dependent adaptation in the NAc.     

Calmodulin dynamically regulates the trafficking of the metabotropic glutamate receptor mGluR5

Metabotropic glutamate receptors (mGluRs) 1–8 are G protein-coupled receptors (GPCRs) that modulate excitatory neurotransmission, neurotransmitter release, and synaptic plasticity. PKC regulates many aspects of mGluR function, including protein–protein interactions, Ca²⁺ signaling, and receptor desensitization. However, the mechanisms by which PKC regulates mGluR function are poorly understood. We have now identified calmodulin (CaM) as a dynamic regulator of mGluR5 trafficking. We show that the major PKC phosphorylation site on the intracellular C terminus of mGluR5 is serine 901 (S901), and phosphorylation of this residue is up-regulated in response to both receptor and PKC activation. In addition, S901 phosphorylation inhibits mGluR5 binding to CaM, decreasing mGluR5 surface expression. Furthermore, blocking PKC phosphorylation of mGluR5 on S901 dramatically affects mGluR5 signaling by prolonging Ca²⁺ oscillations. Thus, our data demonstrate that mGluR5 activation triggers phosphorylation of S901, thereby directly linking PKC phosphorylation, CaM binding, receptor trafficking, and downstream signaling.     

Presynaptic m1 muscarinic receptors are necessary for mGluR long-term depression in the hippocampus

To investigate the role of M1 muscarininc acetylcholine receptors (m1 receptors) in metabotropic glutamate receptor (mGluR)-mediated long-term depression (LTD), we produced mouse lines in which deletion of the m1 gene is restricted to the forebrain (FB–m1KO) or hippocampal CA3 pyramidal neurons (CA3–m1KO). Stimulation in FB–m1KO hippocampal slices resulted in excitatory postsynaptic potentials and long-term synaptic plasticity (long-term potentiation and LTD) similar to controls. The mice were deficient in (S)-3,5-dihydroxyphenylglycine hydrate (DHPG)-induced mGluR LTD, which correlated with a presynaptic increase in the release of neurotransmitters. Protein kinase C (PKC) activity, which is downstream from both mGluRs and m1 receptors, was reduced in CA3 but not in CA1. The presynaptic requirement of m1 receptors was confirmed by the lack of DHPG-induced mGluR LTD in the CA1 of slices from CA3–m1KO mice. mGluR LTD was rescued by stimulating PKC activity pharmacologically in CA3–m1KO mice. These data confirm a role for PKC activation in presynaptic induction of mGluR LTD and distinguish between the roles of mGluRs and m1 receptors.     

Expression of the metabotropic glutamate receptor 5 (mGluR5) induces melanoma in transgenic mice

Glutamate is the major excitatory neurotransmitter in the mammalian CNS and mediates fast synaptic transmission upon activation of glutamate-gated ion channels. In addition, glutamate modulates a variety of other synaptic responses and intracellular signaling by activating metabotropic glutamate receptors (mGluRs), which are G protein-coupled receptors. The mGluRs are also expressed in nonneuronal tissues and are implicated in a variety of normal biological functions as well as diseases. To study mGluR-activated calcium signaling in neurons, we generated mGluR5 transgenic animals using a Thy1 promoter to drive expression in the forebrain, and one founder unexpectedly developed melanoma. To directly investigate the role of mGluR5 in melanoma formation, we generated mGluR5 transgenic lines under a melanocyte-specific promoter, tyrosinase-related protein 1. A majority of the founders showed a severe phenotype with early onset. Hyperpigmentation of the pinnae and tail could be detected as early as 3-5 d after birth for most of the mGluR5 transgene-positive mice. There was 100% penetrance in the progeny from the tyrosinase-related protein 1-mGluR5 lines generated from founders that developed melanoma. Expression of mGluR5 was detected in melanoma samples by RT-PCR, immunoblotting, and immunohistochemistry. We evaluated the expression of several cancer-related proteins in tumor samples and observed a dramatic increase in the phosphorylation of ERK, implicating ERK as a downstream effector of mGluR5 signaling in tumors. Our findings show that mGluR5-mediated glutamatergic signaling can trigger melanoma in vivo. The aggressive growth and severe phenotype make these mouse lines unique and a potentially powerful tool for therapeutic studies.     

TRPM1 is a component of the retinal ON bipolar cell transduction channel in the mGluR6 cascade

An essential step in intricate visual processing is the segregation of visual signals into ON and OFF pathways by retinal bipolar cells (BCs). Glutamate released from photoreceptors modulates the photoresponse of ON BCs via metabotropic glutamate receptor 6 (mGluR6) and G protein (Go) that regulates a cation channel. However, the cation channel has not yet been unequivocally identified. Here, we report a mouse TRPM1 long form (TRPM1-L) as the cation channel. We found that TRPM1-L localization is developmentally restricted to the dendritic tips of ON BCs in colocalization with mGluR6. TRPM1 null mutant mice completely lose the photoresponse of ON BCs but not that of OFF BCs. In the TRPM1-L-expressing cells, TRPM1-L functions as a constitutively active nonselective cation channel and its activity is negatively regulated by Go in the mGluR6 cascade. These results demonstrate that TRPM1-L is a component of the ON BC transduction channel downstream of mGluR6 in ON BCs.     

Prenatal ethanol exposure reduces mGluR5 receptor number and function in the dentate gyrus of adult offspring

BACKGROUND: Previous studies in our laboratory indicated that metabotropic glutamate receptor (mGluR)-stimulated phosphoinositide hydrolysis is markedly reduced in the hippocampal formation of adult rat offspring whose mothers drank moderate amounts of ethanol during pregnancy. In the present study, we extended these observations by measuring the impact of prenatal ethanol exposure on proteins associated with the mGluR5 receptor-effector system along with two mGluR5 agonist-mediated responses in dentate gyrus of adult offspring. METHODS: Sprague-Dawley rat dams consumed one of three diets throughout gestation: (1) a BioServ liquid diet that contained 5% ethanol (v/v), (2) pair-fed an isocalorically equivalent amount of 0% ethanol liquid diet, or (3) lab chow ad libitum. Microdissected slices of dentate gyrus were prepared from adult female offspring from each diet group and used for (1) Western blot analyses of mGluR5, the G-proteins Galphaq and Galpha11, and phospholipase C-beta1; (2) 2-chloro-5-hydroxyphenylglycine (CHPG)-stimulated growth associated protein 43 (GAP-43) phosphorylation; or (3) CHPG potentiation of electrically evoked [H]-D-aspartate (D-ASP) release from dentate gyrus slices. RESULTS: In tissue prepared from untreated control rats, CHPG produced a dose-dependent increase in phosphate incorporation into GAP-43, with maximal agonist stimulation occurring at 20 microM of CHPG. CHPG produced a quantitatively similar dose-dependent increase in the potentiation of electrically evoked D-ASP release from dentate gyrus slices from untreated controls. Fetal ethanol exposure reduced the amount of dentate gyrus mGluR5 receptor protein by 36% compared with the diet control groups. There were no significant differences between diet groups in the two G-proteins or phospholipase C-beta1 protein. Fetal ethanol exposure reduced CHPG-stimulated GAP-43 phosphorylation to approximately one half the amount of CHPG stimulation observed in the control diet groups. Prenatal ethanol exposure also reduced CHPG potentiation of D-ASP release to a similar degree compared with control. CONCLUSIONS: These results indicate that prenatal exposure to moderate quantities of ethanol reduces mGluR5 expression in the dentate gyrus of adult offspring. Although the subcellular site(s) for reduced mGluR5 expression cannot be discerned from Western blot data, the quantitatively similar effects of prenatal ethanol exposure on mGluR5 agonist stimulation of presynaptically localized GAP-43 phosphorylation and CHPG potentiation of evoked D-ASP release suggest that the presynaptic nerve terminal is one site where prenatal ethanol exposure has reduced mGluR5 receptor number and function. Furthermore, these data implicate these neurochemical alterations as one factor contributing to the hippocampal synaptic plasticity and behavioral deficits that we have observed previously in prenatal ethanol-exposed offspring.     

Dendritic glutamate release produces autocrine activation of mGluR1 in cerebellar Purkinje cells

In recent years, it has become clear that, in addition to conventional anterograde transmission, signaling in neural circuits can occur in a retrograde manner. This suggests the additional possibility that postsynaptic release of neurotransmitter might be able to act in an autocrine fashion. Here, we show that brief depolarization of a cerebellar Purkinje cell triggers a slow inward current. This depolarization-induced slow current (DISC) is attenuated by antagonists of mGluR1 or TRP channels. DISC is eliminated by a mixture of voltage-sensitive Ca2+ channel blockers and is mimicked by a brief climbing fiber burst. DISC is attenuated by an inhibitor of vesicular glutamate transporters or of vesicular fusion. These data suggest that Ca2+-dependent postsynaptic fusion of glutamate-loaded vesicles evokes a slow inward current produced by activation of postsynaptic mGluR1, thereby constituting a useful form of feedback regulation.