Role of nitric oxide synthase against MPTP neurotoxicity in mice

Anti-rheumatoid arthritis potential of different fractions derived from of Coluria longifolia

Coluria longifolia Maxim (C. longifolia) is a Chinese folk medication commonly used to treat arthritis and joint pain. Literatures have reported that C. longifolia has significant anti-inflammatory, analgesic and antipyretic effects. The aim of this research was to assay the effective fractions of C. longifolia (EFCL) against rheumatoid arthritis (RA) and to elucidate its anti-RA mechanism on a preliminary basis. The rat model of collagen-induced arthritis (CIA) was established. The therapeutic effects of different fractions in vivo were evaluated by body weight changes, a foot swelling score, inflammatory factors and histopathological examination. The mechanism of EFCL was investigated by activity of oxidative stress related enzyme, qPCR and Western blotting tests. In vivo results showed that total extraction (TE) and n-butanol fraction (NF) could significantly alleviate the symptoms of RA, decrease the levels of IL-6 and TNF-α (P < 0.01), and improve histopathological injury. The mechanism study showed that SOD level was significantly increased with MDA level decreased in the NF group. The upregulated proteins and mRNA expression levels of Nrf2, HO1 and NQO1 after TE and NF administration suggested that the anti-arthritic effect may be related to the Nrf2 signaling pathway and downstream HO1 and NQO1. In conclusion, this study confirmed that C. longifolia is capable of treating RA with NF as the main effective fraction. Its anti-RA action may be associated with Nrf2 signaling pathway and downstream HO1 and NQO1.

Calmodulin and Its Binding Proteins in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disorder that manifests with rest tremor, muscle rigidity and movement disturbances. At the microscopic level it is characterized by formation of specific intraneuronal inclusions, called Lewy bodies (LBs), and by a progressive loss of dopaminergic neurons in the striatum and substantia nigra. All living cells, among them neurons, rely on Ca²⁺ as a universal carrier of extracellular and intracellular signals that can initiate and control various cellular processes. Disturbances in Ca²⁺ homeostasis and dysfunction of Ca²⁺ signaling pathways may have serious consequences on cells and even result in cell death. Dopaminergic neurons are particularly sensitive to any changes in intracellular Ca²⁺ level. The best known and studied Ca²⁺ sensor in eukaryotic cells is calmodulin. Calmodulin binds Ca²⁺ with high affinity and regulates the activity of a plethora of proteins. In the brain, calmodulin and its binding proteins play a crucial role in regulation of the activity of synaptic proteins and in the maintenance of neuronal plasticity. Thus, any changes in activity of these proteins might be linked to the development and progression of neurodegenerative disorders including PD. This review aims to summarize published results regarding the role of calmodulin and its binding proteins in pathology and pathogenesis of PD.

Intranigral Administration of β-Sitosterol-β-D-Glucoside Elicits Neurotoxic A1 Astrocyte Reactivity and Chronic Neuroinflammation in the Rat Substantia Nigra

Chronic consumption of β-sitosterol-β-D-glucoside (BSSG), a neurotoxin contained in cycad seeds, leads to Parkinson's disease in humans and rodents. Here, we explored whether a single intranigral administration of BSSG triggers neuroinflammation and neurotoxic A1 reactive astrocytes besides dopaminergic neurodegeneration. We injected 6 μg BSSG/1 μL DMSO or vehicle into the left substantia nigra and immunostained with antibodies against tyrosine hydroxylase (TH) together with markers of microglia (OX42), astrocytes (GFAP, S100β, C3), and leukocytes (CD45). We also measured nitric oxide (NO), lipid peroxidation (LPX), and proinflammatory cytokines (TNF-α, IL-1β, IL-6). The Evans blue assay was used to explore the blood-brain barrier (BBB) permeability. We found that BSSG activates NO production on days 15 and 30 and LPX on day 120. Throughout the study, high levels of TNF-α were present in BSSG-treated animals, whereas IL-1β was induced until day 60 and IL-6 until day 30. Immunoreactivity of activated microglia (899.0 ± 80.20%) and reactive astrocytes (651.50 ± 11.28%) progressively increased until day 30 and then decreased to remain 251.2 ± 48.8% (microglia) and 91.02 ± 39.8 (astrocytes) higher over controls on day 120. C3(+) cells were also GFAP and S100β immunoreactive, showing they were neurotoxic A1 reactive astrocytes. BBB remained permeable until day 15 when immune cell infiltration was maximum. TH immunoreactivity progressively declined, reaching 83.6 ± 1.8% reduction on day 120. Our data show that BSSG acute administration causes chronic neuroinflammation mediated by activated microglia, neurotoxic A1 reactive astrocytes, and infiltrated immune cells. The severe neuroinflammation might trigger Parkinson's disease in BSSG intoxication.

The role of nitric oxide in brain disorders: Autism spectrum disorder and other psychiatric, neurological, and neurodegenerative disorders

Nitric oxide (NO) is a multifunctional signalling molecule and a neurotransmitter that plays an important role in physiological and pathophysiological processes. In physiological conditions, NO regulates cell survival, differentiation and proliferation of neurons. It also regulates synaptic activity, plasticity and vesicle trafficking. NO affects cellular signalling through protein S-nitrosylation, the NO-mediated posttranslational modification of cysteine thiols (SNO). SNO can affect protein activity, protein-protein interaction and protein localization. Numerous studies have shown that excessive NO and SNO can lead to nitrosative stress in the nervous system, contributing to neuropathology. In this review, we summarize the role of NO and SNO in the progression of neurodevelopmental, psychiatric and neurodegenerative disorders, with special attention to autism spectrum disorder (ASD). We provide mechanistic insights into the contribution of NO in diverse brain disorders. Finally, we suggest that pharmacological agents that can inhibit or augment the production of NO as well as new approaches to modulate the formation of SNO-proteins can serve as a promising approach for the treatment of diverse brain disorders.

Nitric Oxide Signaling in Neurodegeneration and Cell Death

In this tribute to Solomon H. Snyder (Sol) we discuss the mechanisms by which nitric oxide (NO) kills neurons. We provide a historical perspective regarding the discovery that glutamate excitotoxicity is mediated by NO. It also contains a discussion of the discovery that neuronal nitric oxide synthase (nNOS) catalytic activity accounts for NADPH diaphorase activity and its localization in the central nervous system. NADPH diaphorase/nNOS neurons are unique in that they are resistant to toxic effects of excess glutamate and that they are resistant to neurodegeneration in a variety of neurodegenerative diseases. NADPH diaphorase/nNOS neurons are resistant to neurotoxicity and neurodegeneration through the overexpression of manganese superoxide dismutase. The review also delves into the mechanisms by which NO kills neurons including NO's activation of the glyceraldehyde-3-phosphate dehydrogenase-dependent cell pathway. In addition, there is a review of parthanatos in which NO combines with the superoxide anion ( [Formula: see text] ) to form peroxynitrite (ONOO^-) that damages DNA and activates poly (ADP-ribose) (PAR) polymerase (PARP). This ultimately leads to activation of the PARP-dependent apoptosis-inducing factor-associated nuclease, the final executioner in NO-dependent cell death. Finally, there is a discussion of potential targets that are under development that target the mechanisms by which NO kills neurons.

Restoration of intestinal function in an MPTP model of Parkinson's Disease

Patients with Parkinson’s disease often experience non-motor symptoms including constipation, which manifest prior to the onset of debilitating motor signs. Understanding the causes of these non-motor deficits and developing disease modifying therapeutic strategies has the potential to prevent disease progression. Specific neuronal subpopulations were reduced within the myenteric plexus of mice 21 days after intoxication by the intraperitoneal administration of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and was associated with a reduction in stool frequency, indicative of intestinal dysfunction. Oral administration of the divalent copper complex, Cu^II(atsm), which has been shown to be neuroprotective and restore motor performance to MPTP lesioned mice, improved stool frequency and was correlated with restoration of neuronal subpopulations in the myenteric plexus of MPTP lesioned mice. Restoration of intestinal function was associated with reduced enteric glial cell reactivity and reduction of markers of inflammation. Therapeutics that have been shown to be neuroprotective in the central nervous system, such as Cu^II(atsm), therefore also provide symptom relief and are disease modifying in the intestinal tract, suggesting that there is a common cause of Parkinson’s disease pathogenesis in the enteric nervous system and central nervous system.

Protective effect of pitavastatin, a 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, on ischemia-induced neuronal damage

We investigated the neuroprotective effects of a novel 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor (pitavastatin) on ischemic neuronal damage in gerbils using immunohistochemistry. The animals were allowed to survive for 14 days after 5 min of ischemia induced by bilateral occlusion of the common carotid arteries. Five days after ischemia, severe neuronal cell loss was observed in the hippocampal CA1 sector. Prophylactic treatment with pitavastatin dose-dependently prevented the hippocampal CA1 neuronal cell loss 5 days after ischemia. Immunohistochemical study did not show the change of nNOS and iNOS expression in the hippocampus except for, in a few regions, up to 1 day after ischemia. Thereafter, the expression of iNOS was observed in the hippocampal CA1 sector 5 and 14 days after ischemia. In contrast, the expression of nNOS and eNOS gradually decreased in the hippocampal CA1 sector up to 14 days after ischemia. Prophylactic treatment with pitavastatin also prevented the expression of iNOS and the decrease of eNOS expression and the number of nNOS-positive cells in the hippocampal CA1 sector 5 days after ischemia. However, prophylactic treatment with pitavastatin at a dose of 10 mg kg(-1) did not change the immunoreactivity of iNOS and nNOS in the hippocampus at an early phase after ischemia. In contrast, this drug prevented the reduction of eNOS immunoreactivity in the hippocampal CA1 neurons at an early phase after ischemia. These findings demonstrate that the HMG-CoA reductase inhibitor pitavastatin can protect hippocampal CA1 neurons after transient forebrain ischemia through up-regulation of eNOS expression in this region. Thus pharmacological modulation of eNOS expression may offer a novel therapeutic strategy for cerebral ischemic stroke.

SEA0400, a specific Na+/Ca2+ exchange inhibitor, prevents dopaminergic neurotoxicity in an MPTP mouse model of Parkinson's disease

We have recently shown that the Na(+)/Ca(2+) exchanger (NCX) is involved in nitric oxide (NO)-induced cytotoxicity in cultured astrocytes and neurons. However, there is no in vivo evidence suggesting the role of NCX in neurodegenerative disorders associated with NO. NO is implicated in the pathogenesis of neurodegenerative disorders such as Parkinson's disease. This study examined the effect of SEA0400, the specific NCX inhibitor, on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurotoxicity, a model of Parkinson's disease, in C57BL/6J mice. MPTP treatment (10 mg/kg, four times at 2-h intervals) decreased dopamine levels in the midbrain and impaired motor coordination, and these effects were counteracted by S-methylthiocitrulline, a selective neuronal NO synthase inhibitor. SEA0400 protected against the dopaminergic neurotoxicity (determined by dopamine levels in the midbrain and striatum, tyrosine hydroxylase immunoreactivity in the substantia nigra and striatum, striatal dopamine release, and motor deficits) in MPTP-treated mice. SEA0400 had no radical-scavenging activity. SEA0400 did not affect MPTP metabolism and MPTP-induced NO production and microglial activation, while it attenuated MPTP-induced increases in extracellular signal-regulated kinase (ERK) phosphorylation and lipid peroxidation product, thiobarbituric acid reactive substance. These findings suggest that SEA0400 protects against MPTP-induced neurotoxicity probably by blocking ERK phosphorylation and lipid peroxidation which are downstream of NCX-mediated Ca(2+) influx.

The biochemical and cellular basis for nutraceutical strategies to attenuate neurodegeneration in Parkinson's disease

Future therapeutic intervention that could effectively decelerate the rate of degeneration within the substantia nigra pars compacta (SNc) could add years of mobility and reduce morbidity associated with Parkinson’s disease (PD). Neurodegenerative decline associated with PD is distinguished by extensive damage to SNc dopaminergic (DAergic) neurons and decay of the striatal tract. While genetic mutations or environmental toxins can precipitate pathology, progressive degenerative succession involves a gradual decline in DA neurotransmission/synaptic uptake, impaired oxidative glucose consumption, a rise in striatal lactate and chronic inflammation. Nutraceuticals play a fundamental role in energy metabolism and signaling transduction pathways that control neurotransmission and inflammation. However, the use of nutritional supplements to slow the progression of PD has met with considerable challenge and has thus far proven unsuccessful. This review re-examines precipitating factors and insults involved in PD and how nutraceuticals can affect each of these biological targets. Discussed are disease dynamics (Sections 1 and 2) and natural substances, vitamins and minerals that could impact disease processes (Section 3). Topics include nutritional influences on α-synuclein aggregation, ubiquitin proteasome function, mTOR signaling/lysosomal-autophagy, energy failure, faulty catecholamine trafficking, DA oxidation, synthesis of toxic DA-quinones, o-semiquinones, benzothiazolines, hyperhomocyseinemia, methylation, inflammation and irreversible oxidation of neuromelanin. In summary, it is clear that future research will be required to consider the multi-faceted nature of this disease and re-examine how and why the use of nutritional multi-vitamin-mineral and plant-based combinations could be used to slow the progression of PD, if possible.

Involvement of nitric oxide in nigrostriatal dopaminergic system degeneration: a neurochemical study

The present study was undertaken to explore the involvement of nitric oxide (NO) in the 6-hydroxydopamine (6-OHDA) experimental model of Parkinson's disease (PD) in rats. The effect of pharmacological manipulation of the NO system was evaluated on striatal dopamine (DA) level decrease produced by the toxin. 7-nitroindazole (7-NI, 50 mg/kg i.p.; n= 5) pretreatment significantly restored the striatal DA contents. Conversely, 40 mg/kg i.p. of molsidomine (MOL, n= 5), an NO donor, significantly worsened the neurodegeneration (n= 5) and completely counteracted the neuroprotective effect of 7-NI (n= 5). Thus, a crucial role for NO in 6-OHDA induced neurodegeneration is suggested together with a protective benefit for inhibitors of NOS in the treatment of PD.

Neuronal nitric oxide synthase: structure, subcellular localization, regulation, and clinical implications

Nitric oxide (NO), a free gaseous signaling molecule, is involved in the regulation of the cardiovascular, nervous and immune system. The neurotransmitter function of nitric oxide is dependent on dynamic regulation of its biosynthetic enzyme, nitric oxide synthase (NOS). There are three types of NOS, neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS). Of the three NOS, we focus on nNOS in the present review. Brain nNOS exists in particulate and soluble forms and the differential subcellular localization of nNOS may contribute to its diverse functions. Proteins bearing PDZ domains can interact directly with the PDZ domain of nNOS, influencing the subcellular distribution and/or activity of the enzyme. During the past several years, an increasing number of reports have demonstrated the importance of nNOS in a variety of synaptic signaling events. nNOS has been implicated in modulating physiological functions such as learning, memory, and neurogenesis, as well as being involved in a number of human diseases. In this review we concentrate on recent findings regarding the structural features, subcellular localization and factors regulating nNOS function. In particular, we conclude with a section discussing the role of nNOS in a wide range of physiological and pathological conditions.

Neurochemical pathways involved in the protective effects of nicotine and ethanol in preventing the development of Parkinson's disease: potential targets for the development of new therapeutic agents

In this short review, neurochemical targets are identified where nicotine, and possibly ethanol, may interact to prevent the occurrence of Parkinson's disease. These are (a) the nicotinic acetycholine receptors present in the nigrostriatal area or on the surface of microglia, (b) monoamine oxidases and (c) inducible nitric oxide synthase. If such induced changes can be verified in clinical studies, this may help in the design of new therapeutic drugs which may be of relevance to diminish the incidence and perhaps the progression of the debilitating condition of Parkinson's disease.

Protective action of neuronal nitric oxide synthase inhibitor in the MPTP mouse model of Parkinson's disease

We examined the effects of 7-nitroindazole on the dopaminergic system in mice after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. The mice received four intraperitoneal injections of MPTP (20 mg/kg) at 2 h-intervals. Administration of 7-nitroindazole showed dose-dependent neuroprotective effects against striatal dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) depletion 7 days after MPTP treatment. Behavioral testing showed that MPTP-treated mice exhibited motor deficits in the catalepsy test after 7 days, but 7-nitroindazole prevented the appearance of motor abnormalities in this test. The MPTP-treated mice exhibited the loss of tyrosine hydroxylase-containing dopaminergic neurons in mice after 1, 3 and 7 days, but 7-nitroindazole-treated mice showed a protective effect. GFAP (glial fibrillary acidic protein)-positive astrocytes were accumulated in the striatum 3 and 7 days and in the substantia nigra 1, 3 and 7 days after MPTP treatment. In contrast, 7-nitroindazole prevented a significant increase in the number of GFAP-positive astrocytes in the striatum and substantia nigra after MPTP treatment. The reactive astrocytes in the striatum and substantia nigra after MPTP treatment increased the production of S100beta protein, which is thought to promote neuronal damage, but 7-nitoindazole suppressed the expression of S100 beta protein. Activation of microglia, with an increase in staining intensity and morphological changes, was observed in the striatum and substantia nigra 1 and 3 days after MPTP treatment, but 7-nitroindazole prevented a significant increase in the number of isolectin B(4) positive microglia in the striatum and substantia nigra. On the other hand, nestin-immunoreactive cells were increased significantly in the striatum 3 and 7 days after MPTP treatment. 7-Nitroindazole treatment facilitated nestin expression in the striatum 7 days after MPTP treatment. Thus, nNOS inhibitor 7-nitroindazole protected dopaminergic neurons against MPTP neurotoxicity in mice and ameliorated neurological deficits. The results suggest that the neuroprotection is mediated though the modulation of glial activation, including the inhibition of S100beta synthesis and the prevention of microglial activation. These results suggest the therapeutic strategy targeted to glial modulation with 7-nitoindazole offers a great potential for the development of new neuroprotective therapies for Parkinson's disease.

Evidence for Hydroxyl Radical Scavenging Action of Nitric Oxide Donors in the Protection Against 1-Methyl-4-phenylpyridinium-induced Neurotoxicity in Rats

In the present study we provide evidence for hydroxyl radical (*OH) scavenging action of nitric oxide (NO*), and subsequent dopaminergic neuroprotection in a hemiparkinsonian rat model. Reactive oxygen species are strongly implicated in the nigrostriatal dopaminergic neurotoxicity caused by the parkinsonian neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). Since the role of this free radical as a neurotoxicant or neuroprotectant is debatable, we investigated the effects of some of the NO* donors such as S-nitroso-N-acetylpenicillamine (SNAP), 3-morpholinosydnonimine hydrochloride (SIN-1), sodium nitroprusside (SNP) and nitroglycerin (NG) on in vitro *OH generation in a Fenton-like reaction involving ferrous citrate, as well as in MPP+-induced *OH production in the mitochondria. We also tested whether co-administration of NO* donor and MPP+ could protect against MPP+-induced dopaminergic neurotoxicity in rats. While NG, SNAP and SIN-1 attenuated MPP+-induced *OH generation in the mitochondria, and in a Fenton-like reaction, SNP caused up to 18-fold increase in *OH production in the latter reaction. Striatal dopaminergic depletion following intranigral infusion of MPP+ in rats was significantly attenuated by NG, SNAP and SIN-1, but not by SNP. Solutions of NG, SNAP and SIN-1, exposed to air for 48 h to remove NO*, when administered similarly failed to attenuate MPP+-induced neurotoxicity in vivo. Conversely, long-time air-exposed SNP solution when administered in rats intranigrally, caused a dose-dependent depletion of the striatal dopamine. These results confirm the involvement of *OH in the nigrostriatal degeneration caused by MPP+, indicate the *OH scavenging ability of NO*, and demonstrate protection by NO* donors against MPP+-induced dopaminergic neurotoxicity in rats.

7-nitroindazole protects striatal dopaminergic neurons against MPP+-induced degeneration: an in vivo microdialysis study

The neuropathological hallmark of Parkinson's disease (PD) is the selective degeneration of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNc). In this study, using a microdialysis technique, we investigated whether an inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitrindazole (7-NI), could protect against DAergic neuronal damage induced by in vivo infusion of 1-methyl-4-phenylpiridinium iodide (MPP(+)) in freely moving rats. Experiments were performed over 2 days in three groups of rats: (a) nonlesioned, (b) MPP(+)-lesioned, and (c) 7-NI pretreated MPP(+)-lesioned rats. On day 1, control rats were perfused with an artificial CSF, while 1 mM MPP(+) was infused into the striatum for 10 min in the other two groups. The infusion of the MPP(+) produced a neurotoxic damage of the SNc DA neurons and increased striatal DA levels. On day 2, 1 mM MPP(+) was reperfused for 10 min into the striata of each rat group and DA levels were measured as an index of neuronal cell integrity. The limited rise of DA following MPP(+) reperfusion in the MPP(+)-lesioned rats was due to toxin-induced neuronal loss and was reversed by pretreatment with 7-NI (50 mg/kg, intraperitoneally) on day 1, indicating a neuroprotective effect by inhibiting NO formation. These results indicate that neuronally derived NO partially mediates MPP(+)-induced neurotoxicity. The similarity between the MPP(+) model and PD suggests that NO may play a significant role in its etiology.

Immunohistochemical study on distribution of NF-kappaB and p53 in gerbil hippocampus after transient cerebral ischemia: effect of pitavastatin

We investigated the immunohistochemical alterations of the transcription nuclear factor kappa-B (NF-kappaB) and transcription factor p53 in the hippocampus after transient cerebral ischemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor pitavastatin against the alterations of NF-kappaB, p53 and neuronal nuclei in the hippocampus after ischemia. Severe neuronal damage was observed in the hippocampal CA1 neurons 5 and 14 days after ischemia. In the present study, the increase of NF-kappaB immunoreactivity in glial cells and p53 immunoreactivity in neurons preceded neuronal damage in the hippocampal CA1 sector after ischemia. Thereafter, NF-kappaB immunoreactivity was induced highly in reactive astrocytes and microglia of the hippocampal CA1 sector where severe neuronal damage was observed. Our immunohistochemical study showed that pitavastatin prevented the alterations of NF-kappaB and p53 in the hippocampal CA1 sector 5 days after transient ischemia. Furthermore, our results with neuronal nuclei immunostaining indicate that pitavastatin dose-dependently prevented the neuronal cell death in the hippocampal CA1 sector 5 days after transient cerebral ischemia. These results suggest that the up-regulations of NF-kappaB in glia and p53 in neurons can cause neuronal cell death after ischemia. Our findings also support the hypothesis that NF-kappaB- and/or p53-mediated neuronal cell death is prevented through decreasing oxidative stress by pitavastatin. Thus, NF-kappaB and p53 may provide an attractive target for the development of novel therapeutic approaches for brain stroke.

Evidence that quinolinic acid severely impairs energy metabolism through activation of NMDA receptors in striatum from developing rats

In the present study we investigated the effect of intrastriatal administration of 150 nmol quinolinic acid to young rats on critical enzyme activities of energy production and transfer, as well as on 14CO2 production from [1-14C]acetate at distinct periods after quinolinic acid injection. We observed that quinolinic acid injection significantly inhibited complexes II (50%), III (46%) and II-III (35%), as well as creatine kinase (27%), but not the activities of complexes I and IV and citrate synthase in striatum prepared 12 h after treatment. In contrast, no alterations of these enzyme activities were observed 3 or 6 h after quinolinic acid administration. 14CO2 production from [1-14C]acetate was also significantly inhibited (27%) by quinolinic acid in rat striatum prepared 12 h after injection. However, no alterations of these activities were observed in striatum homogenates incubated in the presence of 100 microm quinolinic acid . Pretreatment with the NMDA receptor antagonist MK-801 and with creatine totally prevented all inhibitory effects elicited by quinolinic acid administration. In addition, alpha-tocopherol plus ascorbate and the nitric oxide synthase inhibitor l-NAME completely abolished the inhibitions provoked by quinolinic acid on creatine kinase and complex III. Furthermore, pyruvate pretreatment totally blocked the inhibitory effects of quinolinic acid injection on complex II activity and partially prevented quinolinic acid-induced creatine kinase inhibition. These observations strongly indicate that oxidative phosphorylation, the citric acid cycle and cellular energy transfer are compromised by high concentrations of quinolinic acid in the striatum of young rats and that these inhibitory effects were probably mediated by NMDA stimulation.

Postischemic Alterations of BDNF, NGF, HSP 70 and Ubiquitin Immunoreactivity in the Gerbil Hippocampus: Pharmacological Approach

1. We investigated the immunohistochemical alterations of BDNF, NGF, HSP 70 and ubiquitin in the hippocampus 1 h to 14 days after transient cerebral ischemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor pitavastatin against the changes of BDNF, NGF, HSP 70 and ubiquitin in the hippocampus after cerebral ischemia in the hippocampus after ischemia. 2. The transient cerebral ischemia was carried out by clamping the carotid arteries with aneurismal clips for 5 min. 3. In the present study, the alteration of HSP 70 and ubiquitin immunoreactivity in the hippocampal CA1 sector was more pronounced than that of BDNF and NGF immunoreactivity after transient cerebral ischemia. In double-labeled immunostainings, BDNF, NGF and ubiquitin immunostaining was observed both in GFAP-positive astrocytes and MRF-1-positive microglia in the hippocampal CA1 sector after ischemia. Furthermore, prophylactic treatment with pitavastatin prevented the damage of neurons with neurotrophic factor and stress proteins in the hippocampal CA1 sector after ischemia. 4. These findings suggest that the expression of stress protein including HSP 70 and ubiquitin may play a key role in the protection against the hippocampal CA1 neuronal damage after transient cerebral ischemia in comparison with the expression of neurotrophic factor such as BDNF and NGF. The present findings also suggest that the glial BDNF, NGF and ubiquitin may play some role for helping surviving neurons after ischemia. Furthermore, our present study indicates that prophylactic treatment with pitavastatin can prevent the damage of neurons with neurotrophic factor and stress proteins in the hippocampal CA1 sector after transient cerebral ischemia. Thus our study provides further valuable information for the pathogenesis after transient cerebral ischemia.

Alterations of the expression and activity of midbrain nitric oxide synthase and soluble guanylyl cyclase in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism in mice

The study was aimed at investigating the expression and the activity of neuronal nitric oxide synthase, and of soluble guanylyl cyclase and phosphodiesterase activities that regulate guanosine 3',5'-cyclic monophosphate level in the midbrain, in a mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections. Adult male mice of the C57/BL strain were given three i.p. injections of physiological saline or three i.p. injections of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine solution in physiological saline at 2 h intervals (summary 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine dose: 40 mg/kg), and were killed 3, 7, or 14 days later. mRNA, protein level, and/or activities of neuronal nitric oxide synthase, soluble guanylyl cyclase, phosphodiesterase and guanosine 3',5'-cyclic monophosphate were determined. Immunohistochemistry showed about 75% decrease in the number of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine showed increased midbrain guanylyl cyclase and total nitric oxide synthase activities at 3, 7, and 14 days post-treatment. The specific neuronal nitric oxide synthase inhibitor 7-nitroindazole (10 microM) and the specific inducible nitric oxide synthase inhibitor 1400W (10 microM) inhibited the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced excess in nitric oxide synthase activity by 63-70 and 13-25%, respectively. The increases in total midbrain nitric oxide synthase activity were accompanied by elevated guanosine 3',5'-cyclic monophosphate, enhanced expression of neuronal nitric oxide synthase and of the beta1 subunit of guanylyl cyclase at both mRNA and protein levels that persisted up to the end of the observation period, and by enhanced neuronal nitric oxide synthase and guanylyl cyclase beta1 immunoreactivities in substantia nigra pars compacta 7 and 14 days after the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment. The increases in guanylyl cyclase activity were found to occur exclusively due to increased maximal enzyme activity. No 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced change in phosphodiesterase activity has been detected in any brain region studied. 7-Nitroindazole prevented a significant increase in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced midbrain guanosine 3',5'-cyclic monophosphate level and neurodegeneration of dopaminergic neurons. These results raise the possibility that the nitric oxide/guanylyl cyclase/guanosine 3',5'-cyclic monophosphate signaling pathway may play a role in maintaining dopaminergic neurons function in substantia nigra pars compacta.

Neuroprotective effect of arundic acid, an astrocyte-modulating agent, in mouse brain against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes the damage of dopaminergic neurons as seen in Parkinson's disease. Oxidative stress has been as one of several pathogenic hypotheses for Parkinson's disease. Here we investigated whether arundic acid, an astrocyte-modulating agent, can protect against alterations of nitric oxide synthase (NOS) and superoxide dismutase (SOD) expression on MPTP neurotoxicity in mice, utilizing an immunohistochemistry. For this purpose, anti-tyrosine hydroxylase (TH) antibody, anti-dopamine transporter (DAT) antibody, anti-Cu/Zn-SOD antibody, anti-Mn-SOD antibody, anti-nNOS antibody, anti-eNOS antibody and anti-iNOS antibody were used. The present study showed that the arundic acid had a protective effect against MPTP-induced neuronal damage in the striatum and substantia nigra of mice. The protective effect may be, at least in part, caused by the reductions of the levels of reactive nitrogen (RNS) and oxygen species (ROS) against MPTP neurotoxicity. These results suggest that the pharmacological modulation of astrocyte may offer a novel therapeutic strategy for the treatment of Parkinson's disease. Furthermore, our results provide further evidence that a combination of nNOS inhibitors, iNOS inhibitors and free radical scavengers may be effective in the treatment of neurodegenerative diseases. Thus our present results provide valuable information for the pathogenesis of degeneration of the nigrostriatal dopaminergic neuronal pathway.

Dopamine transporter-mediated cytotoxicity of 6-hydroxydopamine in vitro depends on expression of mutant alpha-synucleins related to Parkinson's disease

6-Hydroxydopamine (6-OHDA) is widely used to produce animal models of Parkinson's disease (PD) by selectively destroying the nigro-striatal dopaminergic systems, but selective toxicity of 6-OHDA towards dopaminergic cells in vitro remains controversial. Mutant (A30P and A53T) alpha-synuclein isoforms cause increased vulnerability of cells towards various toxic insults and enhance dopamine transporter (DAT)-mediated toxicity of the selective dopaminergic neurotoxin and mitochondrial complex I inhibitor MPP(+) in vitro. Here we extend our recent studies on DAT-mediated toxicity to elucidate the mechanisms involved in selective dopaminergic toxicity of 6-OHDA. We studied the cytotoxicity as well as the toxic mechanisms of 6-OHDA in human embryonic kidney HEK-293 cells ectopically co-expressing mutant alpha-synucleins and the human DAT protein. 6-OHDA showed half-maximal toxic concentration (TC(50)) of 88 microM in HEK-hDAT cells without alpha-synuclein expression after 24 h, whereas the TC(50) values significantly decreased to 58 and 39 microM by expression of A30P and A53T alpha-synuclein, respectively. alpha-Synuclein expression did not affect 6-OHDA toxicity in HEK-293 cells not expressing the DAT. Analysis of intracellular parameters of cellular energy metabolism revealed that the co-expression of mutant alpha-synucleins in HEK-hDAT cells accelerates the reduction of intracellular net ATP levels and ATP/ADP ratios induced by 6-OHDA. Uptake function of the DAT was not altered by expression of alpha-synuclein isoforms. Our data suggest a mechanism of 6-OHDA-induced dopaminergic toxicity involving an interaction of mutant alpha-synucleins with the DAT molecule and subsequent acceleration of cellular energy depletion that might be relevant for the pathogenesis of PD.

Alterations of interneurons of the gerbil hippocampus after transient cerebral ischemia: effect of pitavastatin

We investigated the immunohistochemical alterations of parvalbumin (PV)-expressing interneurons in the hippocampus after transient cerebral ischemia in gerbils in comparison with neuronal nitric oxide synthase (nNOS)-expressing interneurons. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor pitavastatin against the damage of neurons and interneurons in the hippocampus after cerebral ischemia. Severe neuronal damage was observed in the hippocampal CA1 pyramidal neurons 5 and 14 days after ischemia. The PV immunoreactivity was unchanged up to 2 days after ischemia. At 5 and 14 days after ischemia, in contrast, a conspicuous reduction of PV immunoreactivity was observed in interneurons of the hippocampal CA1 sector. Furthermore, a significant decrease of PV immunoreactivity was found in interneurons of the hippocampal CA3 sector. No damage of nNOS-immunopositive interneurons was detected in the gerbil hippocampus up to 1 day after ischemia. Thereafter, a decrease of nNOS immunoreactive interneurons was found in the hippocampal CA1 sector up to 14 days after ischemia. Pitavastatin significantly prevented the neuronal cell loss in the hippocampal CA1 sector 5 days after ischemia. Our immunohistochemical study also showed that pitavastatin prevented significant decrease of PV- and nNOS-positive interneurons in the hippocampus after ischemia. Double-labeled immunostainings showed that PV immunoreactivity was not found in nNOS-immunopositive interneurons of the brain. The present study demonstrates that cerebral ischemia can cause a loss of both PV- and nNOS-immunoreactive interneurons in the hippocampal CA1 sector. Our findings also show that the damage to nNOS-immunopositive interneurons may precede the neuronal cell loss in the hippocampal CA1 sector after ischemia and nNOS-positive interneurons may play some role in the pathogenesis of cerebral ischemic diseases. Furthermore, our present study indicates that pitavastatin can prevent the damage of interneurons in the hippocampus after cerebral ischemia. Thus, our study provides valuable information for the pathogenesis after cerebral ischemia.

Distribution of oxidation enzyme eNOS and myeloperoxidase in primary open angle glaucoma

Genetic factors and the influence of superoxide are known to play roles in the etiology of glaucoma. We evaluated the association between primary open angle glaucoma (POAG) and two polymorphisms in the epithelial nitric oxide synthase (eNOS) gene, and one polymorphism in the myeloperoxidase (MPO) gene. We enrolled 66 patients with POAG and 100 healthy volunteers in this study. The polymorphisms in the eNOS and the polymorphism MPO -463 G-to-A in the MPO gene were resolved by polymorphism polymerase chain reaction (PCR). There were no significant differences in the distribution of the eNOS intron -4 (P=0.481), eNOS promotor -786 (P=0.555), and MPO -463 (P=0.292) gene polymorphisms between the POAG patients and the volunteers (P-values=0.481, 0.555, and 0.292, respectively). None of the alleles from either gene differed between the groups (P-values=0.483, 0.554, and 0.183, respectively). Superoxide is closely related to glaucoma, and eNOS and MPO are two important enzymes in the free radical pathway. However, polymorphisms of the eNOS intron-4, eNOS promotor -786, and MPO -463 gene polymorphisms did not reveal significant differences between POAG patients and controls in our study. The use of these agents and other superoxide-related genes for clinical applications requires further investigation.

Effects of age on immunohistochemical changes in the mouse hippocampus

We investigated the age-related changes in neuronal cell death and synaptophysin of the hippocampal CA1 sector in mice using immunohistochemistry. Microtubule-associated protein 2a, b (MAP2) and synaptophysin immunoreactivity was measured in 2-, 8-, 18-, 42- and 59-week-old mice. MAP2 immunoreactivity was unchanged in the hippocampal CA1 sector up to 42 weeks after birth. In 59-week-old mice, however, a significant decrease in MAP2 immunoreactivity was observed in the hippocampal CA1 sector. Total number of synaptophysin-positive boutons was also unchanged in the hippocampal CA1 sector up to 42 weeks of birth. In 59-week-old mice, however, a significant increase in synaptophysin-positive boutons was observed in the hippocampal CA1 sector. These results demonstrate that dendrites and axons in the hippocampal CA1 neurons are particularly susceptible to ageing processes. In contrast, a marked increase in synaptophysin-positive boutons was found in the hippocampal CA1 sector of aged mice. These findings suggest that increase in synaptophysin-positive boutons may play a role in the maintenance of the structural components in the hippocampal CA1 sector of aged mice although most postsynaptic CA1 pyramidal neurons are generated. Thus, our findings provide further valuable information on age-related neurodegeneration and deficits in hippocampus-dependent memory and synaptic plasticity.

Neuroprotective effect of the angiotensin-converting enzyme inhibitor perindopril in MPTP-treated mice

The angiotensin -converting enzyme (ACE) inhibitor perindopril has been shown to exert beneficial effects on the dopaminergic system. Here, we investigated the effects of perindopril on the dopaminergic system in mice after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment, in comparison with a Ca(2+) antagonist, amlodipine. Administration of perindopril showed dose-dependent neuroprotective effects against MPTP-induced striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) depletion. However, administration of amlodipine showed no significant effects on striatal dopamine depletion after MPTP treatment. In our immunohistochemical studies with antibodies against tyrosine hydroxylase (TH), microtubule-associated protein 2a, b (MAP2), dopamine transporter (DAT), parvalbumin (PV), glial fibrillary acidic protein (GFAP) and Cu/Zn-superoxide dismutase (Cu/Zn-SOD), the administration of perindopril significantly attenuated MPTP-induced substantia nigra and striatal damage. This drug also blocked the increases in GFAP-positive astrocytes in the striatum and substantia nigra after MPTP treatment. Furthermore, the administration of perindopril showed a protective effect against the intense Cu/Zn-SOD immunoreactivity in the neurons and glial cells in both the striatum and substantia nigra after MPTP treatment. These results indicated that the ACE inhibitor perindopril can protect against MPTP-induced striatal dopamine and DOPAC depletion in mice. The protective effect may be, at least in part, caused by the reduction of free radicals caused by MPTP. The present study also demonstrated that perindopril is effective against MPTP-induced neurodegeneration of the nigro-striatal dopaminergic pathway. Furthermore, our results provided further evidence that free radical scavengers may be effective in the treatment of neurodegenerative diseases such as Parkinson's disease.

Effect of angiotensin-converting enzyme inhibitor perindopril on interneurons in MPTP-treated mice

We examined the effects of perindopril on the dopaminergic system in mice after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment. The mice received four intraperitoneal injections of MPTP at 1-h intervals. Administration of perindopril showed dose-dependent neuroprotective effects against striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) depletion 3 days after MPTP treatment. Our immunohistochemical study showed that MPTP can severe damage in tyrosine hydroxylase (TH)-immunoreactive neurons after MPTP treatment. The administration of perindopril significantly attenuated MPTP-induced substantia nigra and striatal damage. The present study also showed that the immunoreactivity of parvalbumin (PV)- or neuronal nitric oxide synthase (nNOS)-positive cells in the substantia nigra was decreased 7 days after MPTP treatment, whereas no significant changes were observed in these cells of the striatum throughout the experiments. The administration of perindopril significantly attenuated MPTP-induced decrease of the PV- or nNOS-immunoreactivity in the nigral cells. In double-labeled immunostaining with anti-PV and anti-nNOS antibody, PV-immunoreactive cell bodies and fibers were not double-labeled for nNOS-immunoreactive cell bodies and fibers in both the striatum and substantia nigra after MPTP treatment. Furthermore, PV- or nNOS-immunoreactive cell bodies and fibers in both the striatum and substantia nigra were not double-labeled for TH-immunoreactive cell bodies and fibers. These results demonstrate that the ACE inhibitor perindopril has a dose-dependent protective effect against MPTP-induced striatal dopamine, DOPAC and HVA depletion in mice. The present study also demonstrates that perindopril is effective against MPTP-induced degeneration of the nigral neurons and interneurons. Furthermore, our immunohistochemical study suggests that PV-immunoreactive cells and nNOS-immunoreactive cells are different interneurons in both the striatum and substantia nigra. Thus, our results provide further evidence that the ACE inhibitor perindopril may offer a novel therapeutic strategy for Parkinson's disease (PD).

Upregulation of guanylyl cyclase expression and activity in striatum of MPTP-induced parkinsonism in mice

The aim of our study was to investigate the expression and the activity of soluble guanylyl cyclase (GC) and phosphodiesterase (PDE) activities that regulate cGMP level in the striatum, hippocampus, and brain cortex in an animal model of PD, induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We observed the increase of total activity and protein level of GC in striatum after MPTP injection. It was accompanied by an enhancement of both mRNA expression and protein level of GCbeta1 subunit. MPTP induces mRNA expression and elevates protein concentration of GCbeta1 in striatum up to 14 days after its injection, which in turn causes a marked enhancement of cGMP formation. Furthermore, the activation of GC occurs through change of maximal enzyme activity (V(max)). Simultaneously, no change in PDE activity has been detected in all investigated regions of the brain after MPTP. MPTP injection caused the elevation of GCbeta1 protein level in both the membrane and cytosol fractions being significantly higher in cytosol. Western blot analysis demonstrated about 45-67% decrease of tyrosine hydroxylase protein content in striatum. These data suggest that NO/cGMP signaling pathway may at least partially contribute to dopaminergic fiber degeneration in the striatum, the damage attributed to PD.

Non-invasive imaging of GFAP expression after neuronal damage in mice

Up-regulation of glial fibrillary acidic protein (GFAP) expression is often used as a surrogate marker of neuronal damage. We have created a transgenic mouse line that carries the luciferase gene under the transcriptional control of the mouse GFAP promoter. Biophotonic imaging was used to non-invasively detect the increase in GFAP expression after kainic acid induced neuronal cell death. We demonstrate that after kainic acid treatment, strong biophotonic signals were detected from the brain area. This correlated with both endogenous GFAP and luciferase RNA levels as well as with hippocampal cell death observed histologically. The transgenic mouse line will provide a powerful tool to dynamically monitor neuronal cell death in the living animal and will aid in the discovery and development of drugs to treat damage due to stroke and other neurodegenerative diseases.

Effect of pitavastatin against expression of S100beta protein in the gerbil hippocampus after transient cerebral ischaemia

AIM AND METHODS

We investigated the immunohistochemical alterations of S100beta-, S100-, glial fibrillary acidic protein (GFAP)- and isolectin B4-positive cells in the hippocampus after 5 min of transient cerebral ischaemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor pitavastatin against neuronal damage in the hippocampal CA1 sector after ischaemia.

RESULTS

Severe neuronal damage was observed in the hippocampal CA1 pyramidal neurons from 5 days after ischaemia. GFAP-positive cells increased gradually in the hippocampus from 5 days after ischaemia. Five and 14 days after ischaemia, significant increases in the number of GFAP-positive cells and isolectin B4-positive cells were observed in the hippocampal CA1 and CA3 sector. Mild increases in the number of S100 and S100beta-positive cells were observed in the hippocampal CA1 sector from 1 h to 2 days after ischaemia. Thereafter, S100beta-positive cells increased in the hippocampal CA1 sector after ischaemia, whereas S100-positive cells decreased in this region. In our double-labelled immunostainings, S100 and S100beta immunoreactivity was found in GFAP-positive astrocytes, but not in isolectin B4-positive microglia. Pharmacological study showed that HMG-CoA reductase inhibitor, pitavastatin, can protect against the hippocampal CA1 neuronal damage after ischaemia. This drug also prevented increases in the number of GFAP-positive astrocytes, isolectin B4-positive microglia, S100-positive astrocytes and S100beta-positive astrocytes after ischaemia.

CONCLUSION

The present study demonstrates that pitavastatin can decrease the neuronal damage of hippocampal CA1 sector after ischaemia. This beneficial effect may be, at least in part, mediated by inhibiting the expression of astrocytic activation in the hippocampus at the acute phase after ischaemia. Thus the modulation of astrocytic activation may offer a novel therapeutic strategy of ischaemic brain damage.

Biochemical, behavioral and immunohistochemical alterations in MPTP-treated mouse model of Parkinson's disease

The biochemical, behavioral and immunohistochemical manifestations were investigated in mice subjected to four experimental schedules with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) hydrochloride treatment. The mice were treated intraperitoneally with MPTP (20 mg/kg in saline) four times a day at 2-h intervals showed severe and persistent depletions of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum and behavioral deficits, as compared with those (1) treated with MPTP (15 mg/kg in saline ip) once a day for 14 consecutive days; (2) MPTP (30 mg/kg in saline ip) twice a day for five consecutive days; and (3) MPTP (10 mg/kg in saline ip) four times a day at 1-h intervals for two consecutive days. The immunohistochemical study has shown that the acute treatment with MPTP caused severe loss of tyrosine hydroxylase (TH)- and dopamine transporter (DAT)-immunoreactive dopaminergic neurons and marked increase in glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the striatum and the substantia nigra. Thus acute treatment of mice with MPTP was accompanied by sustained nigral degeneration and motor abnormalities. Furthermore, our results with Cu/Zn-superoxide dismutase (Cu/Zn-SOD) and manganese superoxide dismutase (Mn-SOD) immunostainings suggest that altered capacity of free radicals quenching may play a key role in the development of the neurons and interneuron damage after MPTP neurotoxicity. Thus, our findings provide valuable information on age-related disease progression and mechanisms of neurodegeneration.

7-Nitroindazole blocks conditioned place preference but not hyperactivity induced by morphine

The effects of 7-nitroindazole (7-NI), a neural nitric oxide synthase (nNOS) inhibitor, on spontaneous locomotor activity, morphine-induced hyperactivity, acquisition of place conditioning and morphine-induced conditioned place preference (CPP) were evaluated in male mice. In experiment 1, animals treated with 7-NI (25, 50 and 100mg/kg), morphine (40 mg/kg) or morphine (40 mg/kg) plus 7-NI (25, 50 or 100mg/kg) were placed in an actimeter for 3h. In experiment 2, animals treated with the same drugs and doses were conditioned following an unbiased procedure. 7-NI did not affect the spontaneous locomotor activity or hyperactivity induced by morphine. However, the moderate and high doses of 7-NI produced conditioned place aversion (CPA) and the lowest dose blocked morphine-induced CPP. Our results suggest that nitric oxide is involved in the rewarding properties of morphine but not in its motor effects.

Role of dopamine transporter against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice

We investigated the alterations of dopamine transporter (DAT)-immunopositive cells against MPTP neurotoxicity, in comparison with tyrosine hydroxylase (TH)-immunopositive neurons and glial fibrillary acidic protein (GFAP)-immunopositive cells. This study showed that DAT and TH immunoreactivity was decreased gradually in the striatum and substantia nigra of mice after MPTP treatment. The patterns of the intense TH-immunoreactive fibers and cell bodies were similar to those of DAT-immunoreactive fibers and cell bodies in the striatum and substantia nigra of mice after MPTP treatment. In contrast, GFAP immunoreactivity was increased gradually in the striatum and substantia nigra after MPTP treatment. In our double-labeled immunostaining with anti-DAT and anti-GFAP antibodies, DAT immunoreactivity was observed only in the nigral dopaminergic neurons, but not in the reactive astrocytes. The present results provide further evidence that the functional damage of DAT may precede dopaminergic neuronal death after MPTP treatment, although the decrease in the number of TH-immunopositive neurons was more pronounced than that in the number of DAT-immunopositive neurons. Furthermore, our findings demonstrate that MPTP can selectively injure the dopaminergic neurons which DAT proteins are predominantly distributed on the striatum and substantia nigra. The results provide beneficial information for MPTP-induced neurodegeneration of the nigrostriatal dopaminergic neuronal pathway.