Establishing motor disorder mouse models of Parkinson disease——Comparison of 6-hydroxydompamine and l-methyl-4-phenyl-l,2,3,6-tetrahdropyridine

BACKGROUND: At present, pathogenesis and mechanism of Parkinson disease (PD) are still unclear. Animal models of PD are essential tools in studies on etiology and therapy and should mimic the chronic pathological process, histological characteristics and motor behavior dysfunction. In recent years, transgenic mice have been widely utilized to study the mechanism of PD, and it has become imperative that a PD mouse model of motor behavioral dysfunction be established. OBJECTIVE: To compare the behavioral and histochemical characters of two neurotoxic mice model induced with 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenyl-1, 2, 3, 6 -tetrahydropyridine (MPTP), and a better method to mimic Parkinson disease will be found out. DESIGN: Parallel experiment. SETTING: Laboratory of Molecular Genetics, Department of Medical Genetics, Shanghai Jiao Tong University. MATERIALS: Sixty 129Sv/C57BL6J male wild mice, SPF grade, 8–12 weeks old, weighing 20–25 g, were provided by Experimental Animal Center, Shanghai Jiao Tong University. All the surgery operation was performed according to the rules of Shanghai Jiaotong University Animal Committee. METHODS: The experiment was carried out in the Laboratory of Molecular Genetics (National Key Laboratory), Department of Medical Genetics, Shanghai Jiao Ttong University from March to August 2006. ① Thirty-two male mice were randomly divided into control group and drug treatment group with 16 mice in each group. Surgery was carried out and 6-OHDA was administrated to substantia nigra pars compacta (SNpc) and nigra-striatum pathway according to the different parameters with intoxication apparatus. Saline was injected to the other 16 mice according to the same paradigm. 1 mg/kg apomorphine was injected intraperitoneally 2 weeks later after surgery to induce the imbalanced rotation behavior for 40 minutes. ② Twenty-eight mice were randomly divided into 4 groups with 7 in each group, including low-dose, moderate-dose, high-dose groups and negative control group. Then, mice in the drug treatment group were injected intraperitoneally with 5, 10 and 15 mg/kg MPTP for 9 successive days. In addition, mice in the control group were injected with the same volume of saline for 9 days. Pole test and stride length test were utilized to detect coordinative behavioral dysfunction. Mice were sacrificed 20 days after MPTP treatment, and histochemical staining of tyrosine hydroxynase (TH) was used to observe the loss of dopaminergic neuron in SNpc. MAIN OUTCOME MEASURES: ① Success ratio of each model establishment method; ② inducible asymmetric cycle behavior test 2 weeks after 6-OHDA injection; ③ behavioral dysfunction in pole test and stride length, morphological changes in brain tissue. RESULTS: Totally sixty mice were used in this experiment and 3 mice were excluded because of the hypersensitivity or the clumsy reaction in motor behavioral detection before MPTP treatment, therefore, data was analyzed with the rest 57 mice. ① Lethal ratio: Three out of 16 mice died in striatum injection group and 5 out of 16 mice died in nigro-striatal pathway group. No mouse died in MPTP treatment groups. ② Locomotor behavior: No dysfunction of locomotor was found in 6-OHDA treatment groups. However, several motor behavioral dysfunction were start to present at the 4th day of MPTP injection. ③ Asymmetric cycle behavior: No asymmetric cycle was induced successfully two weeks after 6-OHDA surgery. Mice show hypersensitive behavior 10 minutes after apomorphine injection, which lasted for about 20 minutes. ④ Pole test: From the 4th day of MPTP treatment, mice started to display coordinate dysfunction, such as climbing down along the pole in spiral, moving slowly with hesitation. Some mice could not grab the pole and slide down along the pole at 4th day post injection. Comparing with 0 dose control group, all the three drug treatment groups show significant different dysfunction from the 4th day to the 20th day post injection (P < 0.01). ⑤ stride length test: Mice's stride length decreased, when treated with MPTP, and the mice in the high dose group displayed obviously. ⑥ Dopaminergic neuron stained with TH in nigra pars compacta: The results indicated that administrated MPTP (from low dose to high dose) by intraperitoneal cause chronic lesions on the dopaminergic neuron in the SNpc. CONCLUSION: PD mice models induced with 6-OHDA show high mortality ratio and no asymmetric cycle was found after apomorphine injection. However, injection of MPTP intraperitoneally can simulate the chronic pathway of PD, typical histological changes are found and stable motor behavioral dysfunctions are displayed.     

Intrastriatal glial cell line-derived neurotrophic factors for protecting dopaminergic neurons in the substantia nigra of mice with Parkinson disease

BACKGROUND: Substantia nigra is deep in position and limited in range, the glial cell line-derived neurotrophic factor (GDNF) injection directly into substantia nigra has relatively greater damages with higher difficulty. GDNF injection into striatum, the target area of dopaminergic neuron, may protect the dopaminergic neurons in the compact part of substantia nigra through retrograde transport. OBJECTIVE: To investigate the protective effect of intrastriatal GDNF on dopaminergic neurons in the substantia nigra of mice with Parkinson disease (PD), and analyze the action pathway. DESIGN: A controlled observation. SETTING: Neurobiological Laboratory of Xuzhou Medical College. MATERIALS: Twenty-four male Kunming mice of 7–8 weeks old were used. GDNF, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were purchased from Sigma Company (USA); LEICAQWin image processing and analytical system. METHODS: The experiments were carried out in the Neurobiological Laboratory of Xuzhou Medical College from September 2005 to October 2006. The PD models were established in adult KunMing mice by intraperitoneal injection of MPTP. The model mice were were randomly divided into four groups with 6 mice in each group: GDNF 4-day group, phosphate buffer solution (PSB) 4-day group, GDNF 6-day group and PSB 6-day group. Mice in the GDNF 4 and 6-day groups were administrated with 1 μL GDNF solution (20 μg/L, dispensed with 0.01 mol/L PBS) injected into right striatum at 4 and 6 days after model establishment. Mice in the PSB 4 and 6-day groups were administrated with 0.01 mol/L PBS of the same volume to the same injection at corresponding time points. ② On the 12th day after model establishment, the midbrain tissue section of each mice was divided into 3 areas from rostral to caudal sides. The positive neurons of tyroxine hydroxylase (TH) and calcium binding protein (CB) with obvious nucleolus and clear outline were randomly selected for the measurement, and the number of positive neurons in unit area was counted. MAIN OUTCOME MEASURES: Number of positive neurons of TH and CB in midbrain substantia nigra of mice in each group. RESULTS: All the 24 mice were involved in the analysis of results. The numbers of TH+ and CB+ neurons in the GDNF 4-day group (54.33±6.92, 46.33±5.54) were obviously more than those in the PBS 4-day group (27.67±5.01, 21.50±5.96, P < 0.01). The numbers of TH+ and CB+ neurons in the GDNF 6-day group (75.67±5.39, 69.67±8.69) were obviously more than those in the PBS 6-day group (27.17±4.50, 21.33±5.72, P < 0.01) and those in the GDNF 4-day group (P < 0.01). CONCLUSION: Intrastriatal GDNF can protect dopaminergic neurons in substantia nigra of PD mice, and it may be related to the increase of CB expression.     

Discovery of nigral dopaminergic neurogenesis in adult mice

Parkinson’s disease is characterized by the loss of dopaminergic neurons in the substantia nigra. As a result, intensive efforts have focused upon mechanisms that facilitate the death of mature dopaminergic neurons. Unfortunately, these efforts have been unsuccessful in providing an effective treatment to address neu-rodegeneration in this disease. Therefore, alternative theories of pathogenesis are being explored. Adult neurogenesis of dopaminergic neurons is an attractive concept that would provide a possible mechanism of neurodegeneration as well as offer an endogenous means to replenish affected neurons. To determine whether dopaminergic neurons experience neurogenesis in adult mice we developed a novel cell lineage tracing model that permitted detection of neurogenesis without many of the issues associated with pop-ular techniques. Remarkably, we discovered that dopaminergic neurons are replenished in adult mice by Nestin+/Sox2- progenitor cells. What’s more, the rate of neurogenesis is similar to the rate of dopaminergic neuron loss reported using a chronic, systemic inlfammatory response mouse model. This observation may indicate that neuron loss in Parkinson’s disease results from inhibition of neurogenesis.     

JAK/STAT信号转导通路在IGF-1抑制左旋多巴诱导的多巴胺能神经元凋亡中的作用

Objective To explore the protective effect of insulin-like growth factor 1 (IGF-1) on apoptosis of dopaminergic neurons induced by L-dopa via JAK/STAT signaling pathway. Methods PC12 cells were induced to differentiate into dopaminergic neurons with 100 μg/L β-NGF; MTT assay was employed to identify the changes in the viability of PC12 cells following L-dopa treatment at 0, 10,20, 50, 100, 150 and 200 μmol/L, and the different concentrations of IGF-1 at 0, 10, 25, 50 and 100 nmol/L with the same concentration of L-dopa (150 μmol/L); Western blotting was used to detect the levels of P-JAK2/P-STAT3 in PC12 cells treated with PBS (controls), L-dopa, L-dopa+IGF-1 and L-dopa+IGF-1+AG490 for 24 h, and then the apoptosis rate was assessed by flow cytometry and Hchest33258 staining. Results Western blotting showed that the expressions of P-JAK2 and P-STAT3 were detected in the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups but not in the control group or L-dopa treatment group; the expression of P-STAT3 in the L-dopa+IGF-1+AG490 treatment group was obviously lower than that in the L-dopa+IGF-1 treatment group (P<0.05). Hchest33258 staining indicated that L-dopa treatment group had the most obvious karyopyknosis and karyorrhexis,much more apoptotic bodies than the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups. Flow cytometry showed that the apoptosis rate was significantly different among the 4 groups (F=180.991,P=0.000): as compared with the control group, the other 3 groups had a higher apoptosis rate (P<0.05);L-dopa treatment group (38.13 ±2.54 %) enjoyed the highest level, followed by L-dopa+IGF-1 +AG490treatment group (25.60±1.30 %) and L-dopa+IGF-1 treatment group (20.17±1.54 %). Conclusion L-dopa has toxic effect on PC12 cells; IGF-1 could protect the PC12 cells from the neurotoxic effect of L-dopa and JAK2/STAT3 signaling pathway is activated in this procedure.     

JAK/STAT信号转导通路在IGF-1抑制左旋多巴诱导的多巴胺能神经元凋亡中的作用

Objective To explore the protective effect of insulin-like growth factor 1 (IGF-1) on apoptosis of dopaminergic neurons induced by L-dopa via JAK/STAT signaling pathway. Methods PC12 cells were induced to differentiate into dopaminergic neurons with 100 μg/L β-NGF; MTT assay was employed to identify the changes in the viability of PC12 cells following L-dopa treatment at 0, 10,20, 50, 100, 150 and 200 μmol/L, and the different concentrations of IGF-1 at 0, 10, 25, 50 and 100 nmol/L with the same concentration of L-dopa (150 μmol/L); Western blotting was used to detect the levels of P-JAK2/P-STAT3 in PC12 cells treated with PBS (controls), L-dopa, L-dopa+IGF-1 and L-dopa+IGF-1+AG490 for 24 h, and then the apoptosis rate was assessed by flow cytometry and Hchest33258 staining. Results Western blotting showed that the expressions of P-JAK2 and P-STAT3 were detected in the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups but not in the control group or L-dopa treatment group; the expression of P-STAT3 in the L-dopa+IGF-1+AG490 treatment group was obviously lower than that in the L-dopa+IGF-1 treatment group (P<0.05). Hchest33258 staining indicated that L-dopa treatment group had the most obvious karyopyknosis and karyorrhexis,much more apoptotic bodies than the L-dopa+IGF-1 and L-dopa+IGF-1+AG490 treatment groups. Flow cytometry showed that the apoptosis rate was significantly different among the 4 groups (F=180.991,P=0.000): as compared with the control group, the other 3 groups had a higher apoptosis rate (P<0.05);L-dopa treatment group (38.13 ±2.54 %) enjoyed the highest level, followed by L-dopa+IGF-1 +AG490treatment group (25.60±1.30 %) and L-dopa+IGF-1 treatment group (20.17±1.54 %). Conclusion L-dopa has toxic effect on PC12 cells; IGF-1 could protect the PC12 cells from the neurotoxic effect of L-dopa and JAK2/STAT3 signaling pathway is activated in this procedure.     

共聚物-1对帕金森病模型小鼠多巴胺能神经元的保护作用

目的探讨共聚物-1(Cop-1)免疫或致敏淋巴细胞移植对帕金森病模型小鼠黑质多巴胺(DA)神经元的保护作用。方法选用雄性C57BL/6J小鼠随机分为Cop-1/BSA免疫组、Cop-1/BSA致敏淋巴细胞移植组、MPTP模型组和正常对照组。Cop-1/BSA免疫组在注射MPTP之前10天接受Cop-1/BSA抗原免疫;Cop-1/BSA致敏淋巴细胞移植组动物在MPTP末次注射后,立即接受Cop-1/BSA致敏淋巴细胞移植;MPTP模型组动物仅接受MPTP注射;正常对照组动物仅接受生理盐水注射。MPTP末次注射7天后处死动物,取脑。酪氨酸羟化酶免疫组化及体视学方法定量分析黑质DA神经元数。结果 MPTP注射显著地减少了模型动物黑质DA神经元数量。Cop-1免疫和Cop-1致敏淋巴细胞移植明显增加了MPTP模型动物黑质DA神经元数,对黑质DA神经元有保护作用。BSA免疫或BSA致敏淋巴细胞移植则没有表现出这种保护作用。结论在C57BL/6J小鼠,Cop-1免疫和Cop-1致敏淋巴细胞移植可有效对抗MPTP毒性,保护黑质DA神经元。     

Ethanol extract from Gynostemma pentaphyllum ameliorates dopaminergic neuronal cell death in transgenic mice expressing mutant A53T human alpha-synuclein

Gynostemma(G.) pentaphyllum(Cucurbitaceae) contains various bioactive gypenosides. Ethanol extract from G. pentaphyllum(GP-EX) has been shown to have ameliorative effects on the death of dopaminergic neurons in animal models of Parkinson's disease(PD) induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-and 6-hydroxydopamine. PD patients exhibit multiple symptoms, so PD-related research should combine neurotoxin models with genetic models. In the present study, we investigated the ameliorative effects of GP-EX, including gypenosides, on the cell death of dopaminergic neurons in the midbrain of A53 T α-synuclein transgenic mouse models of PD(A53 T). Both GP-EX and gypenosides at 50 mg/kg per day were orally administered to the A53 T mice for 20 weeks. α-Synuclein-immunopositive cells and α-synuclein phosphorylation were increased in the midbrain of A53 T mice, which was reduced following treatment with GP-EX. Treatment with GP-EX modulated the reduced phosphorylation of tyrosine hydroxylase, extracellular signal-regulated kinase(ERK1/2), Bcl-2-associated death promoter(Bad) at Ser112, and c-Jun N-terminal kinase(JNK1/2) due to α-synuclein overexpression. In the A53 T group, GP-EX treatment prolonged the latency of the step-through passive avoidance test and shortened the transfer latency of the elevated plus maze test. Gypenosides treatment exhibited the effects and efficacy similar to those of GP-EX. Taken together, GP-EX, including gypenosides, has ameliorative effects on dopaminergic neuronal cell death due to the overexpression of α-synuclein by modulating ERK1/2, Bad at Ser112, and JNK1/2 signaling in the midbrain of A53 T mouse model of PD. Further studies are needed to investigate GP-EX as a treatment for neurodegenerative synucleinopathies, including PD. This study was approved by the Animal Ethics Committee of Chungbuk National University(approval No. CBNUA-956-16-01) on September 21, 2016.     

TFP5/TP5 peptide provides neuroprotection in the MPTP model of Parkinson’s disease

Cyclin-dependent kinase 5 (Cdk5) is a member of the serine-threonine kinase family of cyclin-dependent kinases. Cdk5 is critical to normal mammalian nervous system development and plays important regulatory roles in multiple cellular functions. Recent evidence indicates that Cdk5 is inappropriately activated in sev-eral neurodegenerative conditions, including Parkinson’s disease (PD). PD is a chronic neurodegenerative disorder characterized by the loss of dopamine neurons in the substantia nigra, decreased striatal dopamine levels, and consequent extrapyramidal motor dysfunction. During neurotoxicity, p35 is cleaved to form p25. Binding of p25 with Cdk5 leads deregulation of Cdk5 resulting in number of neurodegenerative pathologies. To date, strategies to speciifcally inhibit Cdk5 hyperactivity have not been successful without affecting normal Cdk5 activity. Here we show that inhibition of p25/Cdk5 hyperactivation through TFP5/TP5, truncated 24-aa peptide derived from the Cdk5 activator p35 rescues nigrostriatal dopaminergic neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP/MPP+) in a mouse model of PD. TP5 pep-tide treatment also blocked dopamine depletion in the striatum and improved gait dysfunction after MPTP administration. The neuroprotective effect of TFP5/TP5 peptide is also associated with marked reduction in neuroinlfammation and apoptosis. Here we show inhibition of Cdk5/p25-hyperactivation by TFP5/TP5 pep-tide, which identiifes Cdk5/p25 as a potential therapeutic target to reduce neurodegeneration in PD.     

Tetrahydropalmatine protects against methamphetamine-induced spatial learning and memory impairment in mice

Objective The purpose of this study was to investigate the effect of methamphetamine (MA) on spatial learning and memory and the role of tetrahydropalmatine (THP) in MA-induced changes in these phenomena in mice. Methods Male C57BL/6 mice were randomly divided into eight groups, according to different doses of MA, different doses of THP, treatment with both MA and THP, and saline controls. Spatial learning and memory were assessed using the Morris water maze. Western blot was used to detect the expression of extracellular signal-regulated protein kinase (ERK) in the mouse prefrontal cortex (PFC) and hippocampus. Results Repeated MA treatment significantly increased the escape latency in the learning phase and decreased the number of platform site crossings in the memory-test phase. ERK1/2 expression was decreased in the PFC but not in the hippocampus of the MA-treated mice. Repeated THP treatment alone did not affect the escape latency, the number of platform site crossings or the total ERK1/2 expression in the brain. Statistically significantly shorter escape latencies and more platform site crossings occurred in MA+THP-treated mice than in MA-treated mice. Conclusion Repeated MA administration impairs spatial learning and memory in mice, and its co-administration with THP prevents this impairment, which is probably attributable to changed ERK1/2 expression in the PFC. This study contributes to uncovering the mechanism underlying MA abuse, and to exploring potential therapies.     

姜黄素对帕金森病小鼠模型黑质多巴胺能神经元损伤的保护作用

目的研究姜黄素对由MPTP诱发的帕金森病小鼠模型的脑保护作用及其可能机制。方法应用免疫组织化学染色法和蛋白质印迹法(Western blotting)分别观察姜黄素干预前后帕金森病小鼠中脑黑质-纹状体系统中酪氨酸羟化酶、胶质纤维酸性蛋白阳性神经元数目的变化,以及酪氨酸羟化酶、诱导型一氧化氮合酶和胶质纤维酸性蛋白表达水平的变化。结果MPTP组小鼠中脑黑质酪氨酸羟化酶和胶质纤维酸性蛋白阳性神经元数目明显减少,与正常对照组及治疗组相比差异有统计学意义(均P<0.05)。经不同剂量(5mg/kg、50mg/kg和150mg/kg)的姜黄素干预治疗后,小鼠中脑纹状体中的酪氨酸羟化酶蛋白表达水平(相对灰度值)明显升高,而黑质中诱导型一氧化氮合酶和胶质纤维酸性蛋白表达水平明显降低,与MPTP组比较差异均有统计学意义(P<0.05);MPTP组与溶剂对照组(MPTP DMSO)之间差异无统计学意义(P>0.05)。结论姜黄素可以有效地拮抗MPTP诱导的帕金森病小鼠模型黑质多巴胺能神经元的丢失,其机制可能与姜黄素降低黑质多巴胺能神经元活性氧含量以及抑制炎症反应等作用有关。     

Postnatal iron overload destroys NA-DA functional interactions

Summary. C57/BL6 mice were administered either postnatal iron (Fe²⁺ 7.5 mg/kg, on postnatal days 10–12) or vehicle, followed by administration of either DSP4 (50 mg/kg, s.c., 30 min after injection of zimeldine, 20 mg/kg, s.c.) or vehicle (saline) at 63 days of age. Three weeks later, iron/vehicle treated, DSP4/vehicle treated mice were injected with either a low dose of MPTP (2 × 20 mg/kg, with a 24-hr interval between injections) or vehicle. Behaviour testing took place a further three weeks (spontaneous behaviour and L-Dopa induced) and two weeks (clonidine-L-Dopa induced) later. Postnatal iron administration exacerbated the bradykinesia induced by MPTP and virtually abolished all spontaneous motor activity in NA-denervated mice that were MPTP-treated. Postnatal iron administration reduced markedly the restoration of motor activity by suprathreshold L-Dopa (20 mg/kg) following a 60-min habituation to the test chambers. Pretreatment with DSP4 effectively eliminated the restorative effect of L-Dopa in the MPTP mice. The synergistic effects of co-administration of clinidine (1 mg/kg) with a subthreshold dose of L-Dopa (5 mg/kg) in elevating the motor activity of MPTP mice were reduced markedly by postnatal iron administration, as well as by pretreatment with DSP4. NA-denervation by DSP4, after postnatal iron treatment, totally abolished the activity-elevating effects of the α-adrenoceptor agonist + DA-precursor combination in MPTP mice, and virtually eliminated these effects in saline (non-MPTP) mice. Postnatal iron administration caused enduring higher levels of total iron content in all the groups with an increased level in mice treated with DSP4 followed by MPTP. These divergent findings confirm the direct influence of NA innervation upon dopaminergic functional expression and indicate a permanent vulnerability both in the noradrenergic and dopaminergic pathways following the postnatal infliction of an iron overload.     

MPTP-induced deficits in motor activity: Neuroprotective effects of the spintrapping agent, α-phenyl-tert-butyl-nitrone (PBN)

Summary In Experiment 1, groups of mice were administered either saline or MPTP (2 × 30mg/kg, s.c., separated by a 24-hr interval) 30min after being injected either PBN (15, 50 or 150mg/kg, s.c., low, medium and high doses, respectively) or L-Deprenyl (0.25 or 10.0mg/kg, s.c., low and high doses, respectively), the reference compound used, or saline. Tests of spontaneous motor activity 14 days later indicated that the MPTP-induced hypokinesia for locomotion and rearing was alleviated by prior administration with PBN (50 or 150mg/kg) or L-Deprenyl (10.0mg/kg); lower doses of PBN (15mg/kg) and L-Deprenyl (0.25mg/kg) did not affect the MPTP-induced deficits. Dopamine (DA) concentrations in the striatum confirmed a more severe loss of DA in the MPTP, PBN(15) + MPTP and Deprenyl(0.25) + MPTP groups than in the control group. Significant protection of DA was observed in the PBN(50) + MPTP, PBN(150) + MPTP and Deprenyl(10) + MPTP groups that did not exhibit an hypokinetic behaviour. In Experiment 2, the effects of repeated treatment with PBN (50mg/kg, s.c. over 12 days), post-MPTP, were studied in aged (15-month-old) and young (3-month-old) mice. Subchronic administration of PBN increased substantially the motor activity of old and young mice that had received MPTP. Aged control (saline) mice showed an activity deficit compared to young control mice; this deficit was abolished by repeated PBN treatment. The results suggest that moderate-to-high doses of PBN whether injected in a single dose prior to MPTP or subchronically following MPTP injections may afford protective effects against both the functional changes and DA-loss caused by MPTP treatment, possibly through an antioxidant mechanism.     

Influence of noradrenaline denervation on MPTP-induced deficits in mice

Summary. C57/BL6 mice were administered either DSP4 (50 mg/kg, s.c., 30 min after injection of zimeldine, 20 mg/kg, s.c.) or vehicle (saline) at 63 days of age. Three weeks later, one group (n = 10) of DSP4-treated and one group of vehicle-treated mice were administered MPTP (2 × 40 mg/kg, s.c., 24 hours between injections; the High dose groups), one group (n = 10) of DSP4-treated and one group of vehicle-treated mice were administered MPTP (2 × 20 mg/kg, s.c., 24 hours between injections; the Low dose groups), and one group (n = 10) of DSP4-treated and one group of vehicle-treated mice were administered vehicle. Three weeks later, all six groups were tested in motor activity test chambers, followed by injections of L-Dopa (20 mg/kg, s.c.), and then tested over a further 360 min in the activity test chambers. It was found that pretreatment with the selective NA neurotoxin, DSP4, deteriorated markedly the dose-dependent motor activity deficits observed in the vehicle pretreated MPTP treated mice. These ‘ultra-deficits’ in the spontaneous motor behaviour of MPTP-treated mice were observed over all three parameters: locomotion, rearing and total activity, and were restricted to the 1^st and 2^nd 20-min periods. Administration of L-Dopa (20 mg/kg) following the 60-min testing of spontaneous behaviour restored the motor activity of Vehicle + MPTP treated mice (neither the Vehicle + MPTP-Low nor the Vehicle + MPTP-High groups differed from the Vehicle–Vehicle group, here) but failed to do so in the DSP4 pretreated mice. Here, a dose-dependent deficit of L-Dopa-induced motor activity (over all three parameters) was obtained thereby offering further evidence of an ‘ultra-deficit’ of function due to previous denervation of the NA terminals. The present findings support the notion that severe damage to the locus coeruleus noradrenergic system, through systemic DSP4, disrupts the facilitatory influence on the nigrostriatal DA system, and interferes with the ability of the nigrostriatal pathway to compensate for or recover from marked injury, MPTP treatment.     

Novel D3 dopamine receptor‐preferring agonist D‐264: Evidence of neuroprotective property in Parkinson's disease animal models induced by 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine and lactacystin

Parkinson's disease (PD), a progressive neurodegenerative movement disorder, is known to be caused by diverse pathological conditions resulting from dysfunction of the ubiquitin‐proteasome system (UPS), mitochondria, and oxidative stress leading to preferential nigral dopamine (DA) neuron degeneration in the substantia nigra. In the present study, we evaluated the novel D3 receptor‐preferring agonist D‐264 in a mouse model of PD to evaluate its neuroprotective properties against both the nigrostriatal dopaminergic toxin 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐ and the proteasome inhibitor lactacystin‐induced dopaminergic degeneration. C57BL/6 male mice either were given MPTP by intraperitoneal injection twice per day for 2 successive days at a dose 20 mg/kg or were microinjected with lactacystin bilaterally (1.25 μg/side) into the medial forebrain bundle (MFB). Pretreatment with D‐264 (1 mg/kg and 5 mg/kg, intraperitoneally, once per day), started 7 days before administration of MPTP or lactacystin. We found that D‐264 significantly improved behavioral performance, attenuated both MPTP‐ and lactacystin‐induced DA neuron loss, and blocked proteasomal inhibition and microglial activation in the substantia nigra (SN). Furthermore, D‐264 treatment was shown to increase the levels of brain‐derived neurotrophic factor (BDNF) and glial cell line‐derived factor (GDNF) in MPTP‐ and lactacystin‐treated mice, possibly indicating, at least in part, the mechanism of neuroprotection by D‐264. Furthermore, pretreatment with the D3 receptor antagonist U99194 significantly altered the effect of neuroprotection conferred by D‐264. Collectively, our study demonstrates that D‐264 can prevent neurodegeneration induced by the selective neurotoxin MPTP and the UPS inhibitor lactacystin. The results indicate that D‐264 could potentially serve as a symptomatic and neuroprotective treatment agent for PD. © 2010 Wiley‐Liss, Inc.     

Effect of novel AMPA antagonist, NS1209, on status epilepticus. An experimental study in rat

The current first line treatment of status epilepticus (SE) is based on the use of compounds that enhance GABAergic transmission or block sodium channels. These treatments discontinue SE in only two-thirds of patients, and therefore new therapeutic approaches are needed. We investigated whether a novel water-soluble AMPA antagonist, NS1209, discontinues SE in adult rats. SE was induced by electrical stimulation of the amygdala or subcutaneous administration of kainic acid. Animals were monitored continuously with video-electroencephalography during SE and drug treatment. We found that NS1209 could be safely administered to rats undergoing electrically induced SE at doses up to 50mg/kg followed by intravenous infusion of 5mg/kg for up to 24h. NS1209 administered as a bolus dose of 10-50mg/kg (i.p. or i.v.) followed by infusion of 4 or 5mg/kg h (i.v.) for 2-24h effectively discontinued electrically induced SE in all animals within 30-60 min, and there was no recurrence of SE after a 24-h infusion. Kainate-induced SE was similarly blocked by 10 or 30 mg/kg NS1209 (i.v.). To compare the efficacy and neuroprotective effects of NS1209 with those of diazepam (DZP), one group of rats received DZP (20mg/kg, i.p. and another dose of 10 mg/kg 6h later). By using the administration protocols described, the anticonvulsant effect of NS1209 was faster and more complete than that of DZP. NS1209 treatment (20 mg/kg bolus followed by 5mg/kg h infusion for 24 h) was neuroprotective against SE-induced hippocampal neurodegeneration, but to a lesser extent than DZP. These findings suggest that AMPA receptor blockade by NS1209 provides a novel and mechanistically complimentary addition to the armamentarium of drugs used to treat SE in humans.     

Cigarette smoke and nicotine protect dopaminergic neurons against the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine Parkinsonian toxin

Epidemiological studies have found a negative association between cigarette smoking and Parkinson's disease (PD). In order to analyze the putative neuroprotective effect of cigarette smoke and nicotine, one of its major constituents, we examined their effects in an animal model of PD provoked by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication. Two groups of mice were chronically exposed to cigarette smoke (a low exposure subgroup and a high exposure subgroup; 5 exposures per day at 2-h intervals), two other groups received nicotine treatment (two doses tested 0.2 and 2 mg/kg, 5 injections i.p. per day at 2-h intervals) and one group placebo. On day 8 after the beginning of the treatment, 4 injections of MPTP hydrochloride (15 mg/kg, i.p., at 2-h intervals) or saline were administered to these animals. Nicotine and cotinine plasmatic concentration was quantified by the HPLC method, and degeneration of the nigrostriatal system was assessed by tyrosine hydroxylase (TH) immunohistochemistry. The loss of dopaminergic neurons induced by MPTP in the substantia nigra was significantly less severe in the chronic nicotine treatment groups (at 0.2 and 2 mg/kg) and the low exposure to cigarette smoke group than in the high exposure to cigarette smoke subgroup and the placebo treated subgroup. In contrast, no preservation of TH immunostaining of nerve terminals was observed in the striatum in any group. This suggests that nicotine and low exposure to cigarette smoke may have a neuroprotective effect on the dopaminergic nigrostriatal system by an as yet unknown mechanism.     

Effect of postnatal iron administration on MPTP-induced behavioral deficits and neurotoxicity: behavioral enhancement by L-Dopa-MK-801 co-administration

Two experiments were performed to investigate the interactive effects of postnatal iron administration and adult MPTP treatment upon the function of C57 Bl/6 mice tested at adult age and to ascertain the possible ameliatory effects of a subthreshold dose of L-Dopa co-administered with different doses of the uncompetitive glutamate antagonist, MK-801. Experiment I indicated that postnatal iron induced marked deficits (hypoactivity), initially, in all three parameters of motor activity at the 5.0 and 7.5 mg/kg doses, and to a lesser extent at the 2.5 mg/kg dose. Later combination with MPTP (2x40 mg/kg) potentiated severely these deficits. During the final period of testing a marked hyperactivity was obtained for the two higher dose groups; this effect was abolished in mice administered MPTP. Experiment II indicated that the deficits in motor activity parameters induced by postnatal iron at 7.5 mg/kg were alleviated in a dose-related manner by the co-administration of the uncompetitive glutamate antagonist, MK-801, with a subthreshold dose of L-Dopa. Postnatal iron (7.5 mg/kg) administration followed by low doses of MPTP (2x20 mg/kg) 3 months later virtually abolished all motor activity. The combination of these compounds increased also the motor activity of mice treated with MPTP (2x20 mg/kg) or mice treated with the combination of postnatal iron and MPTP. The combination of MK-801 with L-Dopa increased locomotor (0.3 mg/kg), rearing (0.1 and 0.3 mg/kg) and total activity (0.3 mg/kg) of iron-treated mice during the initial, hypoactive 30-min period of testing. Locomotor activity (0.1 mg/kg) of MPTP-treated mice was increased too during this period. During the final 30-min period of testing all three parameters of activity (locomotion, 0.3 mg/kg; rearing and total activity, 0.1 and 0.3 mg/kg) were enhanced in the iron-treated mice, locomotion (0.1 mg/kg) and rearing (0.1 mg/kg) in the iron plus MPTP treated mice and only locomotion (0.1 mg/kg) in the MPTP-treated mice. In control mice (vehicle+saline), the higher doses of MK-801 (0.1 and 0.3 mg/kg) enhanced both locomotor and total activity. Analyses of total iron concentration in the frontal cortex and basal ganglia of Fe(2+) and vehicle treated mice indicated that marked elevations basal ganglia iron levels of the 5.0 and 7.5 mg/kg groups, later injected either saline or MPTP, were obtained (Experiment I). In Experiment II, iron concentrations in the basal ganglia were elevated in both the Fe(2+)-sal and Fe(2+)-MPTP groups to 170 and 177% of Veh.-sal values, respectively. There was a significant increase in the frontal cortex of iron-treated mice later administered either saline or MPTP (2x40 mg/kg) in Experiment I as well as in those given iron followed by MPTP (2x20mg/kg) in Experiment II. The implications of iron overload in parkinsonism seem confirmed by the interactive effects of postnatal administration of the metal followed by adult MPTP treatment upon motor activity and the activity-enhancing effects of co-administration of L-Dopa with MK-801.     

Neuroprotective and anti‐inflammatory effects of the adenosine A2A receptor antagonist ST1535 in a MPTP mouse model of Parkinson's disease

Adenosine A_2A receptor antagonists are one of the most attractive classes of drug for the treatment of Parkinson's disease (PD) as they are effective in counteracting motor dysfunctions and display neuroprotective and anti‐inflammatory effects in animal models of PD. In this study, we evaluated the neuroprotective and anti‐inflammatory properties of the adenosine A_2A receptor antagonist ST1535 in a subchronic 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of PD. C57BL/6J mice were repeatedly administered with vehicle, MPTP (20 mg/kg), or MPTP + ST1535 (2 mg/kg). Mice were sacrificed three days after the last administration of MPTP. Immunohistochemistry for tyrosine hydroxylase (TH) and cresyl violet staining were employed to evaluate dopaminergic neuron degeneration in the substantia nigra pars compacta (SNc) and caudate‐putamen (CPu). CD11b and glial fibrillary acidic protein (GFAP) immunoreactivity were, respectively, evaluated as markers of microglial and astroglial response in the SNc and CPu. Stereological analysis for TH revealed a 32% loss of dopaminergic neurons in the SNc after repeated MPTP administration, which was completely prevented by ST1535 coadministration. Similarly, CPu decrease in TH (25%) was prevented by ST1535. MPTP treatment induced an intense gliosis in both the SNc and CPu. ST1535 totally prevented CD11b immunoreactivity in both analyzed areas, but only partially blocked GFAP increase in the SNc and CPu. A_2A receptor antagonism is a new opportunity for improving symptomatic PD treatment. With its neuroprotective effect on dopaminergic neuron toxicity induced by MPTP and its antagonism on glial activation, ST1535 represents a new prospect for a disease‐modifying drug. Synapse, 2010. © 2010 Wiley‐Liss, Inc.