Ⅱ、Ⅲ组亲代型谷氨酸受体激动剂对6-羟基多巴诱导的PC12细胞毒性无保护作用

阐明Ⅱ、Ⅲ组亲代谢型谷氨酸受体(metabotropic glutamate receptors,mGluRs)激动剂对6—羟基多巴(6-hydroxydopamine,6-OHDA)诱导的PC12细胞毒性是否具有保护作用。方法：应用高效液相色谱仪联用荧光检测技术测定谷氨酸浓度，应用四甲基偶氮唑盐(MTT)比色法测定PC12细胞活性。结果：6—OHDA剂量依赖性地诱导PC12细胞释放谷氨酸、减低细胞活性，Ⅱ组mGluRs激动剂DCG—IV和Ⅲ组mGluRs激动剂L-AP4对6—0HDA诱导的PC12细胞释放谷氨酸和细胞活性的降低均无显影响。结论：6—OHDA对多巴胺神经元的损伤作用与其诱导谷氨酸过度释放及其继发的兴奋性神经毒性有关，Ⅱ、Ⅲ组亲代谢型谷氨酸受体激动剂对6—OHDA诱导的PC12细胞毒性无保护作用。     

Ⅱ、Ⅲ组亲代谢型谷氨酸受体激动剂逆转1-甲基-4-苯基吡啶离子抑制C6胶质瘤细胞摄取谷氨酸

目的：探讨Ⅱ、Ⅲ组亲代谢型谷氨酸受体(metabotropic glutamate receptors，mGluRs)激动剂对1-甲基-4-苯基吡啶离子(1-metyl-4-phenylpyridinium，MPP~ )抑制C6胶质瘤细胞摄取谷氨酸(glutamate，Glu)的影响。方法：应用同位素标记法测定C6胶质瘤细胞对培养液中[~3H]-D，L-谷氨酸的摄取。结果：Ⅱ组mGluRs激动剂(2S，2’R，3’R)-2-(2’，3’-di-carboxycyclopropyl)glycine(DCG-Ⅳ)和Ⅲ组mGluRs激动刺L( )-2-amino-4-phosphonobutyric acid(LAP4)100μmol·L~(-1)可以逆转MPP~ 抑制C6胶质瘤细胞摄取Glu的作用，而Ⅱ组mGluRs拮抗剂(RS)-1-Amino-5-phosphonoinan-1-carboxylic acid(APICA)和Ⅲ组mGluRs拮抗剂(RS)-α-methvlserine-O-phosphate(MSOP)可以完全阻断其激动剂的逆转作用。 结论：激活C6胶质瘤细胞上的Ⅱ、Ⅲ组mGluRs可以通过促进谷氨酸转运体摄取Glu、进而降低细胞外液的Glu浓度。     

Ⅱ、Ⅲ组亲代谢型谷氨酸受体激动剂对脂多糖抑制C6胶质瘤细胞摄取谷氨酸的影响

目的探讨Ⅱ、Ⅲ组亲代谢型谷氨酸受体(metabotropic glutamate receptors, mGluRs)激动剂对脂多糖(LPS)抑制C6胶质瘤细胞摄取谷氨酸(glutamate, Glu)的影响.方法应用同位素标记法测定C6胶质瘤细胞对[3H]-D,L-Glu的摄取.应用Hoechst染色法、噻唑蓝比色法(MTT)分别检测C6胶质瘤细胞的凋亡、细胞活力.结果LPS(4、6 μg/Ml)显著抑制C6胶质瘤细胞摄取[3H]-D,L-Glu,抑制率分别达 17.6%和 22.2%.Ⅱ组mGluRs激动剂 DCG-Ⅳ 100 μmol/L 和Ⅲ组mGluRs激动剂L-AP4 100 μmol/L 逆转LPS对C6胶质瘤细胞摄取[3H]-D,L-Glu的抑制作用,这种逆转作用分别被Ⅱ、Ⅲ组mGluRs拮抗剂 APICA和MSOP取消.结论DCG-Ⅳ和L-AP4逆转LPS引起的C6胶质瘤细胞Glu摄取抑制,提示Ⅱ、Ⅲ组mGluRs激动剂通过促进Glu摄取,降低细胞外Glu浓度,从而发挥神经保护作用.     

胆红素对糖尿病大鼠脑中某些生化指标的改善作用

目的探讨糖尿病大鼠脑中某些生化指标的改变及补充生理浓度胆红素的保护作用。方法将Wistar大鼠随机分为对照组、糖尿病组、胆红素组和维生素E组 ,腹腔注射链脲霉素建立糖尿病模型后 ,胆红素组 [1 .1 4 4mg/(kg·d) ]和维生素E组 [30mg/(kg·d) ]分别连续给药 4周后 ,测定全脑组织中的超氧化物歧化酶 (SOD)、一氧化氮 (NO)、一氧化氮合成酶 (NOS)、谷胱甘肽过氧化物酶 (GSH Px)、谷胱甘肽S 转移酶 (GSH ST)、总抗氧化能力 (T AOC)。结果与糖尿病组比较 ,补充生理浓度的胆红素显著增加了SOD、GSH Px和GSH ST活性 ,提高了T AOC ,降低了NOS活性和NO含量。结论补充生理浓度胆红素对糖尿病大鼠的脑组织有一定的保护作用     

Ⅱ、Ⅲ组亲代谢型谷氨酸受体激动剂逆转1-甲基-4-苯基吡啶离子抑制星形胶质细胞摄取谷氨酸

目的 :探讨Ⅱ、Ⅲ组亲代谢型谷氨酸受体(metabotropicglutamatereceptors ,mGluRs)激动剂对 1 甲基 4 苯基吡啶离子 (1 methyl 4 phenylpyridinium ,MPP )抑制星形胶质细胞摄取谷氨酸 (Glu)的影响。方法 :应用同位素标记法测定星形胶质细胞对培养液中 [3 H] D ,L 谷氨酸的摄取 ,应用四氮唑 (MTT)比色法检测星形胶质细胞的活性。结果 :MPP 15 0、2 0 0 μmol·L-1可以明显抑制星形胶质细胞摄取Glu ,抑制率达 5 8.3%和 70 .1% ,但并不影响细胞活性 ;Ⅱ组mGluRs激动剂 (2S ,2’R ,3’R) 2 (2’ ,3’ dicar boxycyclopropyl)glycine (DCG IV ) 0 .1、 1、 10 ,10 0 μmol·L-1和Ⅲ组mGluRs激动剂L( ) 2 amino 4 phosphonobutyricacid (L AP4 ) 1、10、10 0 μmol·L-1可以逆转MPP 对星形胶质细胞摄取Glu的抑制作用。结论 :MPP 抑制星形胶质细胞摄取Glu可能与直接影响谷氨酸转运体 (GluTs)的功能有关 ,激活星形胶质细胞上的Ⅱ、Ⅲ组mGluRs可以通过促进GluTs摄取Glu、进而降低细胞外液的Glu浓度而发挥神经保护作用。     

氯丙烯对大鼠血清中氧化-抗氧化功能的影响

目的探讨氯丙烯亚慢性染毒对大鼠血清中氧化-抗氧化功能的影响。方法选用雄性Wistar大鼠分别以100或200 mg/kg剂量灌胃3个月,测定大鼠血清中还原型谷胱甘肽(GSH)、丙二醛(MDA)、活性氧(ROS)含量和超氧化物歧化酶(T-SOD)、谷胱甘肽过氧化物酶(GSH-Px)、总抗氧化能力(T-AOC)、谷胱甘肽还原酶(GR)活力的变化。结果与对照组相比,大鼠血清中GSH含量及T-SOD、T-AOC、GR活性显著降低,其中低剂量组分别降低13.4%、11.1%、22.4%和16.6%(P<0.01),高剂量组分别降低17.5%、24.6%、34.8%和28.1%(P<0.01);MDA含量及GSH-Px活力有增加趋势(P>0.05);ROS含量低剂量组增加12%(P<0.01),高剂量组增加20%(P<0.01)。结论氯丙烯亚慢性染毒可导致大鼠血清中活性氧成分明显增加,抗氧化能力明显减弱,T-AOC及GR活力变化幅度最大。     

OCE对体外培养的视网膜组织的抗氧化作用

目的：观察不同成份的培养液对成年犬视网膜组织进行体外培养的前后相关生化指标的改变，旨在为视网膜移植提供抗氧化能力的保护性方法。方法：将健康成年家犬74眼随机分成六组，Ⅰ（新鲜视网膜组）Ⅱ（常规培养液组）Ⅲ（高浓度OCE组）Ⅳ（低浓度OCE组）Ⅴ（高浓度全脑组织提取液组Ⅵ（低浓度全脑组织提取液组）培养一周。六组视网膜取材后进行SOD、MDA、G－Px,GST,T－AOC生化指标的测定。结果：Ⅱ组与Ⅰ组SOD、G－Px、GST、T－AOC明显下降；DMA值增多非常显著；Ⅲ、Ⅳ组与Ⅱ组比较，T－AOC、SOD、G－Px、GST值显著增高，Ⅳ组明显高于其它各培养组；Ⅲ、Ⅳ组与Ⅱ组比较，MDA值降低明显，Ⅳ组降低最明显。结论：成年犬OCE中含有清除自由基、增强抗氧化能力的特殊物质。并且低浓度OCE对体外培养的视网膜组织抗氧化作用显著。     

氯化锰染毒大鼠肝脏的一些氧化与抗氧化指标变化

目的探讨氯化锰(MnCl2)染毒大鼠肝脏的一些氧化与抗氧化指标变化。方法使用MnCl26mg/(kg·d)腹腔连续注射分别染毒雄性SD大鼠30d、90d(染毒Ⅰ、Ⅱ组)及染毒90d后停止染毒,继续正常喂养30d组(染毒Ⅲ组)。苏木素-伊红(HE)法染色,光学显微镜下检测大鼠肝组织病理学变化,紫外-可见分光光度法和分子荧光法检测肝组织中丙二醛(MDA)、谷胱甘肽(GSH)含量、谷胱甘肽过氧化物酶(GSH-Px)活性和总抗氧化能力(T-AOC)的变化。结果大鼠染毒MnCl2肝脏组织学损害主要表现为不同程度的肝小叶结构紊乱,变性坏死,炎性细胞浸润。肝脏变性坏死程度中,染毒Ⅱ组明显大于染毒Ⅰ组,染毒Ⅲ组轻于染毒Ⅱ和染毒Ⅰ组;与对照组相比,染毒Ⅰ、Ⅱ组肝脏中MDA含量分别高出26%、78%;GSH含量分别降低24%、31%;GSH-Px活性分别降低22%、38%;T-AOC分别降低39%、60%。染毒Ⅲ组肝脏中以上各指标与对照组相比差异无统计学意义(P0.05)。结论在本试验条件下,氯化锰对大鼠肝脏具有明显的损伤作用,其损伤程度与连续作用时间成正相关,停止染毒一定时间后肝脏的抗氧化能力和病理结构均得到了明显的恢复。     

微透析—高效液相色谱—化学发光法动态监测6—羟基多巴帕金森病模型大鼠纹状体内多巴胺水平

目的:建立动态监测自由清醒大鼠纹状体内多巴胺水平的微透析-高效液相色谱-化学发光分析法，研究天然冰片联合左旋多巴对6-羟基多巴诱导的帕金森病(PD)模型大鼠纹状体内多巴胺水平的影响。方法:雄性SD大鼠随机分为正常组、6-羟基多巴PD模型组、左旋多巴组和天然冰片联合左旋多巴组。模型组大鼠麻醉后于右侧前脑内侧束缓慢注入4μg·μL^-1 6-羟基多巴，术后4周腹腔注射0.5 mg·kg^-1阿扑吗啡，筛选旋转圈数≥7 r·min^-1(或每30 min 210 r)的大鼠作为6-羟基多巴诱导的PD模型动物。采用脑微透析活体采样联用高效液相色谱-化学发光法(HPLC-CL)监测自由清醒大鼠纹状体内多巴胺水平的动态变化。HPLC分离系统包括Shim pack ODS色谱柱(250 mm×4.6 mm, 5μm),三水合乙酸钠缓冲液-乙腈(80∶20)作为流动相，流速为1.0 mL·min^-1,柱温为37℃。CL检测系统包括3μmol·L^-1鲁米诺溶液、稀释1 000倍的纳米金溶液和50μmo...     

阿奇霉素对佐剂性关节炎模型大鼠血清中IL-1、TGF-β的影响

目的:通过检测佐剂性关节炎模型大鼠血清IL-1、TGF-β水平,来探讨阿奇霉素对佐剂性关节炎的治疗作用。方法:将Wistar雌性大鼠随机分成正常组(Ⅰ组)、模型组(Ⅱ组)和阿奇霉素治疗组(Ⅲ组),各15只。分别给予Ⅱ、Ⅲ组大鼠足跖部注射弗氏完全佐剂建立类风湿关节炎模型,Ⅰ组给予同等剂量生理盐水。模型建立后,Ⅲ组腹腔注射阿奇霉素干预,Ⅰ、Ⅱ组给予同等剂量及疗程生理盐水。之后用酶联免疫法对大鼠血清中IL-1、TGF-β水平进行检测。结果:Ⅲ组TGF-β水平明显高于Ⅱ组(P<0.05),IL-1水平明显低于Ⅱ组(P<0.05)。结论:阿奇霉素可降低血清中IL-1的表达水平,升高TGF-β的表达水平,对佐剂性关节炎大鼠有一定的治疗作用。     

Ⅱ组代谢性谷氨酸受体对延髓脑片吸气神经元电活动的影响

目的:探讨Ⅱ组代谢性谷氨酸受体对延髓脑片面神经后核内侧区(mNRF)吸气神经元放电活动的调制作用。方法:制作新生大鼠离体延髓脑片标本,主要包含mNRF,并完整保留舌下神经根,以改良Kreb's液灌流脑片,同步记录舌下神经根呼吸节律性放电活动(RRDA)和吸气神经元的放电活动。待放电活动稳定后,在灌流液中分别单独给予该受体的特异性激动剂APDC和特异性拮抗剂EGLU,并分别观察其对吸气神经元放电活动的影响。结果:给予受体激动剂APDC后,吸气神经元的吸气时程(TI)缩短,放电的积分幅度(IA)减小,单位放电频率(PFn)变慢,呼吸周期(RC)和呼气时程(TE)延长。给予其拮抗剂EGLU后,吸气神经元的TE和RC缩短,PFn明显增加,IA和TI无明显变化。结论:Ⅱ组代谢性谷氨酸受体对离体延髓脑片吸气神经元放电活动有调节作用,其可以通过作用吸气神经元的电活动来参与节律性呼吸的调控。     

Tetramethylpyrazine nitrone improved mitochondrial dysfunction,downregulated α-synuclein,and reduced neurodegeneration in Parkinson disease models

OBJECTIVE The peroxisome proliferatoractivated receptor γ co-activator 1α(PGC-1α) and nuclear factor(erythroid-derived 2)-like 2(Nrf2) are key regulators controlling antioxidant defense, mitochondrial biogenesis and cellular proteostasis. Dysfunction of any of these processes has been implicated in the pathogenesis of Parkinson disease(PD). Activation of PGC-1α/Nrf2 might improve mitochondrial dysfunction, promote α-synuclein(α-syn) clearance, and attenuate degeneration of nigral dopaminergic neurons in PD. To test this, we used tetramethylpyrazine nitrone(TBN), a potent free radical scavenger, to activate PGC-1α/Nrf2 pathway. METHODS 1-Methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine(MPTP)-induced mouse model, unilateral intrastriatal injection of 6-hydroxydopamine(6-OHDA)-induced rat model, and transgenic mice overexpression of human A53 T mutant α-synuclein were used to evaluate TBN's therapeutic efficacy and to explore its mechanisms of action. RESULTS TBN protected against 1-methyl-4-phenylpyridinium(MPP+) and 6-OHDA insult in cultured primary midbrain neurons. TBN promoted α-syn clearance by autophagy and proteasomal pathways in the cell models overexpressed human A53 T mutant α-syn. In MPTP-treated mouse and unilateral 6-OHDA-lesioned rat, as well as in α-syn transgenic mouse model, TBN improved motor impairment, increased survive of nigra dopaminergic neurons, and elevated striatal dopamine level, while decreased the products of oxidative damage.Importantly, TBN down-regulated α-syn level in the brain and serum of α-syn transgenic mice. These improvements in vitro and in vivo were associated with activation of PGC-1α/Nrf2 signal pathway, resulting in reduced oxidative stress, enhanced mitochondrial function, and increased protein clearance. CONCLUSION Our work demonstrates that activation of PGC-1α/Nrf2 by TBN can maintain the survival of nigral dopaminergic neurons, and might be disease-modifying in PD models, providing the critical rationale for further development of TBN for PD treatment.     

梭曼中毒大鼠脂质过氧化损伤及抗氧化剂的作用

目的 以大鼠血清乙酰胆碱酯酶(AChE)活力变化为梭曼(soman)中毒程度指标，研究维生素A和维生素E对急性中毒大鼠的血清、大脑和肝脏组织中超氧化物歧化酶(SOD)、一氧化氮合酶(NOS)和总抗氧化力(T—AoC)的影内，探讨抗氧化剂维生素A和维生素E对梭曼中毒大鼠AChE及脂质过氧化损伤的保护作用。方法 雄性大鼠40只，按体重随机分为阴性对照组、阳性对照组、维生素A组、维生素E组。阴性对照组和阳性对照组每日灌胃5ml/kg的菜籽油；维生素A组每日灌胃2ml/kg的维生素A；维生素E组每日灌胃2．5ml/kg的维生素E，共灌胃9d。第10日除阴性对照组外其余各组大鼠均皮下注射0．9LD50梭曼，2h后断头处死并取样。测定大鼠血清、大脑、肝脏的T—AOC、SOD和NOS及血清AChE活力。结果 梭曼中毒2h后，血清乙酰胆碱酷酶(AChE)及血清、大脑、肝脏组织中SOD活力和T—AoC水平下降，NOS活力提高；维生素A和维生素E均能提高SOD、T—AOC和AChE活力，而降低NOS活力。结论 经皮下注射0．9LD50梭曼可引起AChE活力显著下降，表明大鼠已严重中毒，中毒时伴有明显的脂质过氧化损伤。中毒前大鼠用维生素A和维生素E预处理，能够保护AChE活力，降低NOS活力，减少N0自由基的生成，同时，提高SOD、T—AoC水平。提示维生素A和维生素E对梭曼中毒有较好的预防作用。     

Type I and II metabotropic glutamate receptor agonists and antagonists evoke cardiovascular effects after intrathecal administration in conscious rats.

1. In the present study, the role of metabotropic glutamate receptors (mGluRs) in central cardiovascular regulation in conscious rats was examined. To this end, agonists and antagonists for type I and II mGluRs were administered intrathecally, and the temporal changes in blood pressure and heart rate were recorded. 2. L-glutamate (1 micromol) and the prototypical mGluR agonist (1S,3R)-ACPD (0.1 and 0. 3 micromol) both increased mean arterial pressure (MAP) and heart rate (HR), implicating functional mGluRs in the spinal cord. The type I mGluR agonist DHPG (0.01 - 0.1 micromol) evoked increases in MAP (max=25+/-5 mmHg) and HR (max=88+/-23 beats min-1). The duration of action, but not the maximum effects, were dose-related and ranged from approximately 10 min to <90 min and 1 min to >90 min for MAP and HR, respectively. 3. The type I/II mGluR agonist CCG-1 (0.1 and 0. 3 micromol) caused smaller, variable increases in MAP and HR of intermediate duration (5 - 20 min), whereas the type II MGluR agonist APDC (0.1 and 1.0 micromol) caused marked, but transient (3 - 5 min), pressor and tachycardic responses. The highest doses of DHPG and CCG-1, but not APDC, also evoked behavioural responses similar to a spontaneous nociceptive behavioural effect reported previously. 4. The type I and II mGluR antagonists (AIDA and LY307452, respectively) were also given approximately 5 min before the administration of the respective type I and II mGluR agonists (DHPG and APDC). Both compounds caused pressor and tachycardic responses, with the effect of AIDA, but not LY307452, returning to control levels before mGluR agonist administration. AIDA significantly attenuated the overall cardiovascular effects of DHPG, while LY307452 significantly attenuated the overall cardiovascular effects of APDC. 5. These results indicate that functional type I and II mGluRs exist in the spinal cord, and that their activation evokes prolonged cardiovascular effects.     

The effects of dopamine and dopamine agonists on the release of 3H-GABA and 3H-5HT from rat nigral slices

Only high micromolar concentrations of dopamine and dopamine agonists altered spontaneous and KCl-evoked release of 3H-GABA and 3H-5HT from rat nigral slices in vitro. Apomorphine (100 microM) and dopamine (100 microM) enhanced the spontaneous release of 3H-5HT but the effect of dopamine was not reversed by haloperidol (1 microM). Both apomorphine (100 microM) and dopamine (100 microM) enhanced the KCl-evoked release of 3H-5HT but these effects were not reversed by haloperidol (1 microM). Apomorphine (10-250 microM) and dopamine (10-250 microM) inhibited 3H-5HT uptake into nigral synaptosomal preparations in a concentration-dependent manner. Accordingly, a major portion of the apparent effect of these drugs on 3H-5HT release may be due to inhibition of 3H-5HT uptake. Dopamine (100 and 1000 microM), amphetamine (100 microM), apomorphine (100 microM) and 2-amino-6,7-dihydroxytetralin (ADTN; 100 microM) were without effect on the spontaneous release of 3H-GABA from nigral slices. Apomorphine (100 microM) and ADTN (100 microM) reduced the KCl-evoked release of 3H-GABA from substantia nigra, an effect antagonized by haloperidol (1 microM). However, amphetamine (100 microM) and dopamine (100-1000 microM) were without effect on KCl-evoked 3H-GABA release. These results suggest that only high concentration of some dopamine agonists can modulate 3H-5HT and 3H-GABA release in substantia nigra. However, dopamine either had no effect, or its actions were not reversed by dopamine receptor blockade, so it appears unlikely that dendritic dopamine release will influence GABA and 5HT release in substantia nigra.     

Ginsenoside Rg1 reduces MPTP-induced substantia nigra neuron loss by suppressing oxidative stress

AIM: To investigate the effect of ginsenoside Rg1, an effective ingredient from ginsenoside, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced substantia nigra neuron lesion. METHODS: C57-BL mice were given MPTP to prepare Parkinson disease mice model. Different doses of Rg1 (5, 10, and 20 mg.kg(-1).d(-1)) or N-acetylcystein (NAC) (300 mg.kg(-1).d(-1)) were given 3 d prior to MPTP in the pretreatment groups. Glutathione (GSH) level and total superoxide dismutase (T-SOD) activity in substantia nigra were determined by spectrophotometry. Nissl staining, tyrosine hydroxylase immunostaining, and TUNEL labeling were used to observe the damage and apoptosis of nigral neurons. Western blot analysis was used to detect the phospho-JNK and phospho-c-Jun levels in midbrain homogenates. RESULTS: Pretreatments of C57-BL mice with different doses of Rg1 or NAC were found to protect against MPTP-induced substantia nigra neurons loss. Rg1 or NAC prevented GSH reduction and T-SOD activation in substantia nigra, and attenuated the phosphorylations of JNK and c-Jun following MPTP treatment. CONCLUSION: The antioxidant property of Rg1 along with the blocking of JNK signaling cascade might contribute to the neuroprotective effect of ginsenoside Rg1 against MPTP.     

Neuroprotection by crocetin in a hemi-parkinsonian rat model

Reactive oxygen species (ROS) are implicated as the leading biochemical cause of neuronal death in various neurologic disorders, including Parkinson's disease. In the present study, neuromodulatory effects of crocetin (active constituent of Crocus sativus) in a 6-hydroxydopamine (6-OHDA) model of rat Parkinsonism were investigated. Male Wistar rats were pre-treated with crocetin (25, 50 and 75 microg/kg body weight) for 7 days and subjected to unilateral intrastriatal injection of 10 microg 6-OHDA on day 8. Locomotion and rotation were observed on day 23 post-injection, and after 4 weeks, striatum and substantia nigra were dissected out by decapitation. Activity of antioxidant enzymes and content of dopamine (DA) and its metabolites were estimated in striatum, whereas glutathione (GSH) content and thiobarbituric acid reactive substance (TBARS) were evaluated in substantia nigra. Levels of GSH and dopamine were protected, while TBARS content was attenuated in crocetin-treated groups. The activity of antioxidant enzymes was decreased in the lesion group, but protected in the crocetin-treated groups. These findings were supported by the histopathologic findings in the substantia nigra that showed that crocetin protects neurons from deleterious effects of 6-OHDA. This study revealed that crocetin, which is an important ingredient of diet in India and also used in various systems of indigenous medicine, is helpful in preventing Parkinsonism and has therapeutic potential in combating this devastating neurologic disorder.     

Metabotropic glutamate receptor 2 modulates excitatory synaptic transmission in the rat globus pallidus

While group II metabotropic glutamate receptors (mGluRs) are known to be expressed in the rat globus pallidus (GP), their functions remain poorly understood. We used standard patch clamping technique in GP slices to determine the effect of group II mGluR activation on excitatory transmission in this region. Activation of group II mGluRs with the group-selective agonist DCG-IV or APDC reduced the amplitude of the evoked excitatory postsynaptic currents (EPSCs) and significantly increased the paired pulse ratio suggesting a presynaptic site of action. This was further supported by double-labeling electron microscopy data showing that group II mGluRs (mGluR2 and 3) immunoreactivity is localized in glutamatergic pre-terminal axons and terminals in the GP. Furthermore, we found that LY 487379, an mGluR2-specific allosteric modulator, significantly potentiated the inhibitory effect of DCG-IV on the excitatory transmission in the GP. Co-incubation with 30 microM LY 487379 increased the potency of DCG-IV about 10-fold in the GP. We were thus able to pharmacologically isolate the mGluR2-mediated function in the rat GP using an mGluR2-specific allosteric modulator. Therefore, our findings do not only shed light on the functions of group II mGluRs in the GP, they also illustrate the therapeutic potential of mGluR-targeting allosteric modulators in neurological disorders such as Parkinson's disease.     

Stimulation of high-affinity GTPase activity through group II metabotropic glutamate receptors in rat hippocampal and striatal membranes

The stimulation of high-affinity GTPase activity through metabotropic glutamate receptors (mGluRs) was pharmacologically characterized with the use of a series of agonists for mGluRs in rat hippocampal and striatal membranes. The pharmacological profile of the response was almost identical to each other between both brain regions. Thus, the high-affinity GTPase activities were stimulated by several mGluR-related compounds with the following rank order of potency: (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) = (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I) > L-glutamate = 2R,4R-4-aminopyrrolidine-2,4-dicarboxylate [(2R,4R)-APDC] > (S)-4-carboxy-3-hydroxyphenylglycine [(S)-4C3HPG] = 1S,3R-1-aminocyclopentane-1,3-dicarboxylate [(1S,3R)-ACPD] > (S)-3-carboxy-4-hydroxyphenylglycine [(S)-3C4HPG] = ibotenate. The negative logarithmically transformed EC50 (pEC50) values of these compounds in both brain regions were significantly correlated with those reported previously in the cerebral cortical membranes (N. Nishi et al., Br. J. Pharmacol., 130, 1664-1670, 2000). On the contrary, other reagents including a selective group I mGluRs agonist, (RS)-3,5-dihydroxyphenylglycine [(RS)-3,5-DHPG], and selective group III mGluRs agonists such as L(+)-2-amino-4-phosphonobutylate (L-AP4) and L-serine-O-phosphate (L-SOP) had little or no effects even at the highest concentration examined. Quisqualate was also a very weak agonist in both regions. These results indicate that mGluR-mediated high-affinity GTPase activity derives from the Gi proteins associated with adenylyl cyclase inhibition through group II mGluRs, in particular the mGluR2 subtype, in rat hippocampal and striatal membranes.     

Protective Effects of Chunghyuldan against ROS‐mediated Neuronal Cell Death in Models of Parkinson’s Disease

Abstract: Previous reports have suggested that the herbal medicine Chunghyuldan (CHD, Qingxue‐dan in Chinese and Daio‐Orengedokuto in Japanese) has wide‐ranging biological effects, including anti‐hyperlipidaemic, anti‐ischaemic, anti‐inflammatory and antioxidant activities. Reactive oxygen species (ROS)‐mediated mitochondrial dysfunction is thought to be one of the major pathological mechanisms responsible for Parkinson’s disease (PD) and may underlie the selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) that is a hallmark of this disease. In this study, we examined the neuroprotective effects of CHD in PD models produced by treatment with neurotoxins that act via ROS‐mediated mitochondrial dysfunction. In an in vitro PD model using 6‐hydroxydopamine, CHD applied at concentrations of 10 and 100 μg/ml exhibited significant protective effects in PC12 cells by inhibiting intracellular ROS generation. CHD applied at 10 and 100 μg/ml also prevented 6‐hydroxydopamine‐induced mitochondrial depolarization and elevation of caspase‐3 activity. At the same doses, CHD showed regulatory effects on the haem oxygenase‐1 and gp91 phagocytic oxidase which have critical roles in generating ROS. In addition, CHD protected dopaminergic neurons in a primary mesencephalic culture against MPP+ neurotoxicity. In an in vivo PD model produced by 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine treatment (20 mg/kg, 4 times, i.p.), co‐administration of CHD (50 mg/kg, 5 days, p.o.) ameliorated PD‐like behavioural symptoms (bradykinesia) and reduced dopaminergic neuronal damage in the SNpc and striatum as measured by immunocytochemistry. These results demonstrate the neuroprotective effects of CHD in PD models that are mediated through inhibition of ROS generation and associated mitochondrial dysfunction.