Chronic Rotenone Research Articles

Protection by an antioxidant of rotenone-induced neuromotor decline, reactive oxygen species generation and cellular stress in mouse brain

Exposure to environmental toxins, including rotenone, results in central nervous system and systemic toxicity. Rotenone is a widely used pesticide and a mitochondrial complex I (CI) inhibitor. This study reports effectiveness of a synthetic lipoylcarnitine antioxidant compound, lipoylcarnitine methyl ester iodide (PMX-500F), for treatment of chronic rotenone induced neurological deficits in mice. Mice (C57BL/6NTac; two months of age) received oral administration of rotenone (30mg/kg/day) or vehicle, preceded by intraperitoneal injection of PMX-500F (19mg/kg) or vehicle for four weeks. In the Rota-rod test, rotenone treatment had no effect (P>0.05); however, PMX-500F treatment improved locomotor coordination and endurance (latency to fall time; P<0.05). For neuromuscular strength (wire hang test), rotenone treated mice showed reduced latency to fall compared to control mice (P<0.05). PMX-500F treatment improved the outcome in both control and rotenone exposed mice (P<0.05). Rotenone administration increased ROS generation in the forebrain and midbrain regions, but not in the cerebellum (P<0.05). Co-treatment with PMX-500F normalized the ROS in forebrain and midbrain regions to that of the control concentrations. In rotenone administered mice, activated stress-activated protein kinase/c-Jun NH2-terminal kinase (pSAPK/JNK) was higher in forebrain and midbrain lysates than in control mice (P<0.05) and treatment with PMX-500F reduced pSAPK/JNK to control levels. The pSAPK/JNK levels in the cerebellum were similar in all four groups (P>0.05). Total SAPK/JNK was not altered by either rotenone or PMX-500F treatment (P>0.05). These results illustrate that an antioxidant, here PMX-500F, provides protection against rotenone induced decline in neuromotor function, reactive oxygen species (ROS) generation and cellular stress.

Pramipexole protective effect on rotenone induced neurotoxicity in mice

AbstractIntroduction:Pramipexole is a new dopaminergic drug which has been approved for PD treatment. However, we tried to find a new capacity for this drug rather than symptomatic effect. Materials and Methods: A chronic rotenone model with daily oral dose of 30mg/kg was induced in mice. Pramipexole was tried in a new approach where the treatment began in the middle of rotenone course with oral dose 1mg/kg/day of pramipexole. Results: Further analysis of behavioral tests and immunohistochemistry revealed success of pramipexole in improving the rotenone intoxicated mice. Conclusion: These results showed possible beneficial effects of pramipexole against rotenone-induced neurotoxicity.

Effects of chronic rotenone exposure on enteric neuronal or glial cells in vivo

Effects of chronic rotenone exposure on enteric neuronal or glial cells in vivo

Edaravone Guards Dopamine Neurons in a Rotenone Model for Parkinson's Disease

3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone), an effective free radical scavenger, provides neuroprotection in stroke models and patients. In this study, we investigated its neuroprotective effects in a chronic rotenone rat model for Parkinson's disease. Here we showed that a five-week treatment with edaravone abolished rotenone's activity to induce catalepsy, damage mitochondria and degenerate dopamine neurons in the midbrain of rotenone-treated rats. This abolishment was attributable at least partly to edaravone's inhibition of rotenone-induced reactive oxygen species production or apoptotic promoter Bax expression and its up-regulation of the vesicular monoamine transporter 2 (VMAT2) expression. Collectively, edaravone may provide novel clinical therapeutics for PD.

Rotenone and Paraquat Linked to Parkinson’s Disease: Human Exposure Study Supports Years of Animal Studies

A growing body of evidence suggests pesticides may play a role in Parkinson’s disease (PD) in humans. Self-reported PD has been associated with lifetime use of pesticides, and animal studies have suggested that the pesticides paraquat and rotenone can cause oxidative stress and mitochondrial dysfunction, respectively—posited mechanisms of action in PD—as well as symptoms in rodents similar to human PD. Now, researchers have linked human exposure to paraquat and rotenone with PD [EHP 119(6):866–872; Tanner et al.]. Their study is the first analysis of pesticides classified by presumed mechanism of action rather than by intended use or chemical class. The researchers assessed lifetime use of pesticides as reported by participants in the Agricultural Health Study, a prospective study of private pesticide applicators (mostly farmers) and their spouses in Iowa and North Carolina. In the nested case–control study, neurologists specializing in movement disorders identified 110 people with PD and 358 controls without who were frequency matched by age, sex, and state. The researchers collected detailed information about use of 31 different pesticides as well as covariate information including lifelong smoking and family history of PD. Each pesticide was classified according to its mechanism of action as either an oxidative stressor or a mitochondrial complex I inhibitor. For participants with PD, the researchers considered pesticide use that occurred before their PD diagnosis. For controls, they considered pesticide use that occurred before the median age of PD diagnosis for cases in the corresponding age-, sex-, and state-specific groups. Among the mitochondrial complex I inhibitors studied, the researchers found the strongest association between PD and use of rotenone. Among oxidative stressors, they found the strongest association between PD and use of paraquat. Participants with PD were 2.5 times more likely than controls to have reported use of rotenone or paraquat. The results may have far-reaching implications, considering the widespread use of these pesticides. Paraquat remains one of the most widely used herbicides worldwide, and rotenone was used ubiquitously before most uses were voluntarily stopped in the United States in 2007. Other agents associated with mitochondrial complex I inhibition, such as permethrin, remain in common use. The authors point out several limitations of the study, including the fact that participants reported exposure to many pesticides, and effects of other agents can’t be excluded. However, the associations between PD and paraquat and rotenone remained after adjustment for overall pesticide use. It also was impossible to measure pesticide exposure, only estimate it retrospectively. Future investigations of combinations of pesticides and of other mechanistic groups will be important, as will mechanistic studies that model exposure conditions similar to those occurring in humans.

Neuroprotection of α-synuclein under acute and chronic rotenone and maneb treatment is abolished by its familial Parkinson's disease mutations A30P, A53T and E46K

α-Synuclein (α-Syn) plays a crucial role in the pathophysiology of Parkinson's disease (PD). α-Syn has been extensively studied in many neuronal cell-based PD models but has yielded mixed results. The objective of this study was to re-evaluate the dual cytotoxic/protective roles of α-Syn in dopaminergic SH-SY5Y cells. Stable SH-SY5Y cells overexpressing wild type or familial α-Syn mutants (A30P, E46K and A53T) were subjected to acute and chronic rotenone and maneb treatment. Compared with untransfected SH-SY5Y cells, wild type α-Syn attenuated rotenone and maneb-induced cell death along with an attenuation of toxin-induced mitochondrial membrane potential changes and Reactive Oxygen Species level, whereas the mutant α-Syn constructs exacerbated environmental toxins-induced cytotoxicity. After chronic treatment, wild type α-Syn but not the mutant variants was found to rescue cells from subsequent acute hydrogen peroxide insult. These results suggest that the fundamental property of wild type α-Syn may be protective, and such property may be lost by its familial PD mutations.

Integrating multiple aspects of mitochondrial dynamics in neurons: Age-related differences and dynamic changes in a chronic rotenone model

Changes in dynamic properties of mitochondria are increasingly implicated in neurodegenerative diseases, particularly Parkinson's disease (PD). Static changes in mitochondrial morphology, often under acutely toxic conditions, are commonly utilized as indicators of changes in mitochondrial fission and fusion. However, in neurons, mitochondrial fission and fusion occur in a dynamic system of axonal/dendritic transport, biogenesis and degradation, and thus, likely interact and change over time. We sought to explore this using a chronic neuronal model (nonlethal low-concentration rotenone over several weeks), examining distal neurites, which may give insight into the earliest changes occurring in PD. Using this model, in live primary neurons, we directly quantified mitochondrial fission, fusion, and transport over time and integrated multiple aspects of mitochondrial dynamics, including morphology and growth/mitophagy. We found that rates of mitochondrial fission and fusion change as neurons age. In addition, we found that chronic rotenone exposure initially increased the ratio of fusion to fission, but later, this was reversed. Surprisingly, despite changes in rates of fission and fusion, mitochondrial morphology was minimally affected, demonstrating that morphology can be an inaccurate indicator of fission/fusion changes. In addition, we found evidence of subcellular compartmentalization of compensatory changes, as mitochondrial density increased in distal neurites first, which may be important in PD, where pathology may begin distally. We propose that rotenone-induced early changes such as in mitochondrial fusion are compensatory, accompanied later by detrimental fission. As evidence, in a dopaminergic neuronal model, in which chronic rotenone caused loss of neurites before cell death (like PD pathology), inhibiting fission protected against the neurite loss. This suggests that aberrant mitochondrial dynamics may contribute to the earliest neuropathologic mechanisms in PD. These data also emphasize that mitochondrial fission and fusion do not occur in isolation, and highlight the importance of analysis and integration of multiple mitochondrial dynamic functions in neurons.

The exceptional properties of 9‐methyl‐β‐carboline: stimulation, protection and regeneration of dopaminergic neurons coupled with anti‐inflammatory effects

Beta-carbolines (BCs) are potential endogenous and exogenous neurotoxins that may contribute to the pathogenesis of Parkinson's disease. However, we recently demonstrated protective and stimulatory effects of 9-methyl-BC (9-me-BC) in primary dopaminergic culture. In the present study, treatment with 9-me-BC unmasked a unique tetrad of effects. First, tyrosine hydroxylase (TH) expression was stimulated in pre-existing dopa decarboxylase immunoreactive neurons and several TH-relevant transcription factors (Gata2, Gata3, Creb1, Crebbp) were up-regulated. Neurite outgrowth of TH immunoreactive (THir) neurons was likewise stimulated. The interaction with tyrosine kinases (protein kinase A and C, epidermal growth factor-receptor, fibroblast growth factor-receptor and neural cell adhesion molecule) turned out to be decisive for these observed effects. Second, 9-me-BC protected in acute toxicity models THir neurons against lipopolysaccharide and 2,9-dime-BC(+) toxicity. Third, in a chronic toxicity model when cells were treated with 9-me-BC after chronic rotenone administration, a pronounced regeneration of THir neurons was observed. Fourth, 9-me-BC inhibited the proliferation of microglia induced by toxin treatment and installed an anti-inflammatory environment by decreasing the expression of inflammatory cytokines and receptors. Finally, 9-me-BC lowered the content of alpha-synuclein protein in the cultures. The presented results warrant the exploration of 9-me-BC as a novel potential anti-parkinsonian medication, as 9-me-BC interferes with several known pathogenic factors in Parkinson's disease as outlined above. Further investigations are currently under way.

Metabolic Activity Determines Efficacy of Macroautophagic Clearance of Pathological Oligomeric α-Synuclein

Macroautophagy is an essential degradative pathway that can be induced to clear aggregated proteins, such as those found in Parkinson's disease and dementia with Lewy bodies, a form of Parkinsonism. This study found that both LC3-II and beclin were significantly increased in brains from humans with Dementia with Lewy bodies and transgenic mice overexpressing mutant alpha-synuclein, as compared with respective controls, suggesting that macroautophagy is induced to remove alpha-syn, particularly oligomeric or mutant forms. Aged mutant animals had higher autophagy biomarker levels relative to younger animals, suggesting that with aging, autophagy is less efficient and requires more stimulation to achieve the same outcome. Disruption of autophagy by RNA interference significantly increased alpha-syn oligomer accumulation in vitro, confirming the significance of autophagy in alpha-syn clearance. Finally, rotenone-induced alpha-syn aggregates were cleared following rapamycin stimulation of autophagy. Chronic rotenone exposure and commensurate reduction of metabolic activity limited the efficacy of rapamycin to promote autophagy, suggesting that cellular metabolism is critical for determining autophagic activity. Cumulatively, these findings support the concept that neuronal autophagy is essential for protein homeostasis and, in our system, reduction of autophagy increased the accumulation of potentially pathogenic alpha-synuclein oligomers. Aging and metabolic state were identified as important determinants of autophagic activity. This study provides therapeutic and pathological implications for both synucleinopathy and Parkinson's disease, identifying conditions in which autophagy may be insufficient to degrade alpha-syn aggregates.

Effects of glutamate and α2-noradrenergic receptor antagonists on the development of neurotoxicity produced by chronic rotenone in rats

Systemic inhibition of complex I by rotenone in rats represents a model of Parkinson's disease (PD). The aim of this study was to elucidate whether neramexane (NMDA, nicotinic α9/α10 and 5-HT 3 receptor antagonist), idazoxan (α 2-adrenoceptor antagonist) or 2-methyl-6-(phenyl-ethyl)-pyrimidine (MPEP, metabotropic glutamate receptor 5 antagonist) prevents rotenone-induced parkinsonian-like behaviours and neurochemical changes in rats. Rotenone (2.5 mg/kg i.p. daily) was administered over 60 days together with saline, neramexane (5 mg/kg i.p., b.i.d.), idazoxan (2.5 mg/kg i.p., b.i.d.) or MPEP (2.5 mg/kg i.p., b.i.d.). The same doses of neramexane, idazoxan and MPEP were administered to rats treated with vehicle instead of rotenone. Treatment-related effects on parkinsonian-like behaviours, such as hypokinesia/rigidity and locomotor activity, were evaluated. Moreover, concentrations of dopamine, serotonin and their metabolites were measured in rats from each experimental group. Over the 60-day treatment period, the rotenone + saline treated animals developed hypokinesia, expressed as an increase in the bar and grid descent latencies in the catalepsy test, and a decrease in locomotor activity. Neramexane and idazoxan partially prevented the development of catalepsy in rotenone-treated rats. Co-administration of MPEP with rotenone resulted only in a decrease in descent latency in the grid test on day 60. Chronic rotenone treatment reduced concentrations of dopamine and serotonin in the anterior striatum, which was blocked by co-treatment with neramexane or idazoxan but not with MPEP. Only neramexane treatment blocked the rotenone-induced decrease in dopamine levels in the substantia nigra pars compacta. In conclusion, neramexane and idazoxan counteracted to some extent the development of parkinsonian symptoms and neurochemical alterations in the rotenone model of Parkinson's disease.

Chronic administration of rotenone induces Parkinsonian symptoms and increases levels of nitric oxide in rat brain

Background Parkinson's disease (PD) is one of the most widespread neurodegenerative diseases. A reduction of complex I activity has been demonstrated in mitochondria of PD patients. Recently, it was shown that chronic subcutaneous exposure to low doses of rotenone (an inhibitor of mitochondrial NADH dehydrogenase and a commonly used pesticide) caused highly selective nigrostriatal dopaminergic lesions. However, while the behavioural effects of rotenone administration are well characterised, the mechanisms underlying rotenone action are unclear. Recent studies are regarding nitric oxide (NO) as universal neuronal messenger in the pathophysiology of neurodegenerative diseases. The aim of this work is to study mechanisms underlying oxidative damage of the various brain areas of rats produced by rotenone and to investigate a possible role of NO and lipid peroxidation (LPO) processes during chronic rotenone administration.

Advanced glycation end products induce in vitro cross‐linking of α‐synuclein and accelerate the process of intracellular inclusion body formation

Cross-linking of alpha-synuclein and Lewy body formation have been implicated in the dopaminergic neuronal cell death observed in Parkinson's disease (PD); the mechanisms responsible, however, are not clear. Reactive oxygen species and advanced glycation end products (AGEs) have been found in the intracellular, alpha-synuclein-positive Lewy bodies in the brains of both PD as well as incidental Lewy body disease patients, suggesting a role for AGEs in alpha-synuclein cross-linking and Lewy body formation. The aims of the present study were to determine 1) whether AGEs can induce cross-linking of alpha-synuclein peptides, 2) the progressive and time-dependent intracellular accumulation of AGEs and inclusion body formation, and 3) the effects of extracellular or exogenous AGEs on intracellular inclusion formation. We first investigated the time-dependent cross-linking of recombinant human alpha-synuclein in the presence of AGEs in vitro, then used a cell culture model based on chronic rotenone treatment of human dopaminergic neuroblastoma cells (SH-SY5Y) over a period of 1-4 weeks, in the presence of different doses of AGEs. Cells (grown on coverslips) and cell lysates, collected at the end of every week, were analyzed for the presence of intracellular reactive oxygen species, AGEs, alpha-synuclein proteins, and intracellular alpha-synuclein- and AGE-positive inclusion bodies by using immunocytochemical, biochemical, and Western blot techniques. Our results show that AGEs promote in vitro cross-linking of alpha-synuclein, that intracellular accumulation of AGEs precedes alpha-synuclein-positive inclusion body formation, and that extracellular AGEs accelerate the process of intracellular alpha-synuclein-positive inclusion body formation.

Protection by the NDI1 Gene against Neurodegeneration in a Rotenone Rat Model of Parkinson's Disease

It is widely recognized that mitochondrial dysfunction, most notably defects in the NADH-quinone oxidoreductase (complex I), is closely related to the etiology of sporadic Parkinson's disease (PD). In fact, rotenone, a complex I inhibitor, has been used for establishing PD models both in vitro and in vivo. A rat model with chronic rotenone exposure seems to reproduce pathophysiological conditions of PD more closely than acute mouse models as manifested by neuronal cell death in the substantia nigra and Lewy body-like cytosolic aggregations. Using the rotenone rat model, we investigated the protective effects of alternative NADH dehydrogenase (Ndi1) which we previously demonstrated to act as a replacement for complex I both in vitro and in vivo. A single, unilateral injection of recombinant adeno-associated virus carrying the NDI1 gene into the vicinity of the substantia nigra resulted in expression of the Ndi1 protein in the entire substantia nigra of that side. It was clear that the introduction of the Ndi1 protein in the substantia nigra rendered resistance to the deleterious effects caused by rotenone exposure as assessed by the levels of tyrosine hydroxylase and dopamine. The presence of the Ndi1 protein also prevented cell death and oxidative damage to DNA in dopaminergic neurons observed in rotenone-treated rats. Unilateral protection also led to uni-directional rotation of the rotenone-exposed rats in the behavioral test. The present study shows, for the first time, the powerful neuroprotective effect offered by the Ndi1 enzyme in a rotenone rat model of PD.

Chronic rotenone treatment induces behavioral effects but no pathological signs of parkinsonism in mice

It has been hypothesized that exposures to neurotoxic pesticides together with aging and genetic factors increase the risk for developing Parkinson's disease (PD) which is characterized by a progressive degeneration of the nigrostriatal dopaminergic pathway. Chronic treatment with the pesticide rotenone has been reported to induce parkinsonism in rats. Although transgenic mice (but not transgenic rats) are available to investigate the importance of environmental factors in genetically predisposed animals, the effects of chronic rotenone exposure have so far not been examined in intact mice. Therefore, we investigated the effects of chronic exposure to rotenone (2.5 or 4.0-5.0 mg/kg s.c. for 30-45 days) in mice aged 2.5, 5, or 12 months. During the treatment period, the effects on vitality and motor behavior were investigated. Furthermore, the toxicity of rotenone on dopaminergic nigrostriatal neurons and peripheral tissues was examined. In comparison with control mice, rotenone-treated mice had a decreased spontaneous motor activity, but the density of nigral dopaminergic neurons failed to show any significant changes, except for a tendency to decrease in old mice treated with 4 mg/kg. At the tested doses, rotenone caused a moderate hepatic fatty degeneration. The data indicate that rotenone is not able to cause the neuropathological characteristics of PD in mice under these testing paradigms, which were similar to those of the rotenone rat model. Further studies will have to clarify whether genetic mouse models of PD might be more sensitive to the neurotoxic effects of rotenone.

Standardized Hypericum perforatum reduces oxidative stress and increases gene expression of antioxidant enzymes on rotenone-exposed rats

Since oxidative stress is implicated in the pathophysiology of dementia and depression, this study was designed to investigate the pro-oxidant activity of rotenone, the protective role of standardized extract of Hypericum perforatum (SHP), as well as the mRNA levels of antioxidant enzymes, in brain homogenates of rats following exposure to rotenone and SHP extract. Quercetin in liposomes, one active constituent, was tested in the same experimental conditions to serve as a positive control. The animals received pretreatment with SHP (4 mg/kg) or quercetin liposomes (25 and 100 mg/kg) 60 min before of rotenone injection (2 mg/kg). All treatments were given intraperitoneally in a volume of 0.5 ml/kg body weight, for 45 days. Rotenone treatment increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and levels of malondialdehyde (MDA). The content of reduced glutathione (GSH) was decreased due to chronic rotenone treatment. Rotenone significantly induced the gene expression of CuZnSOD, MnSOD; CAT and GPx in brain. In contrast, SHP extract exerted an antioxidant action which was related with a decreased of MnSOD activity and mRNA levels of some antioxidant enzymes evaluated. Liposomal quercetin treatment resulted in a significant preservation of the activities of antioxidant enzymes and a decreased in the mRNA levels of these antioxidant enzymes. One possible mechanism of action of SHP extract may be related to quercetin in protecting neurons from oxidative damage. Therefore standardized extract of H. perforatum could be a better alternative for depressed elderly patients with degenerative disorder exhibiting elevated oxidative stress status.

Chromatographic analysis of dopamine metabolism in a Parkinsonian model

The present study examined the metabolism of released dopamine from rat striatum upon chronic rotenone exposure. The sample separation was carried out by two-dimensional, reversed-phase and ion pair reversed-phase chromatography using on-line solid phase extraction enrichment. Reduced dopamine content and decreased extracellular level of [ 3H] and endogenous dopamine evoked by electrical stimulation indicated the injury of dopaminergic pathway. Sensitivity of dopaminergic neurons were increased to oxidative stress with enhanced release of dopamine and formation of oxidized metabolite dopamine quinone (DAQ). Utilizing multidimensional detection, EC at −100 mV reduction potential, the method has been applied for identification of DAQ and aminochrome (DAC).

Intersecting pathways to neurodegeneration in Parkinson's disease: Effects of the pesticide rotenone on DJ-1, α-synuclein, and the ubiquitin–proteasome system

Sporadic Parkinson's disease (PD) is most likely caused by a combination of environmental exposures and genetic susceptibilities, although there are rare monogenic forms of the disease. Mitochondrial impairment at complex I, oxidative stress, alpha-synuclein aggregation, and dysfunctional protein degradation, have been implicated in PD pathogenesis, but how they are related to each other is unclear. To further evaluated PD pathogenesis here, we used in vivo and in vitro models of chronic low-grade complex I inhibition with the pesticide rotenone. Chronic rotenone exposure in vivo caused oxidative modification of DJ-1, accumulation of alpha-synuclein, and proteasomal impairment. Interestingly, the effects become more regionally restricted such that systemic complex I inhibition eventually results in highly selective degeneration of the nigrostriatal pathway. DJ-1 modifications, alpha-synuclein accumulation, and proteasomal dysfunction were also seen in vitro and these effects could be prevented with alpha-tocopherol. Thus, chronic exposure to a pesticide and mitochondrial toxin brings into play three systems, DJ-1, alpha-synuclein, and the ubiquitin-proteasome system, and implies that mitochondrial dysfunction and oxidative stress link environmental and genetic forms of the disease.

Energy Status, Ubiquitin Proteasomal Function, and Oxidative Stress During Chronic and Acute Complex I Inhibition with Rotenone in Mesencephalic Cultures

Complex I impairment with rotenone produces damage though a mechanism thought to be distinct from effects on mitochondrial respiration. The outcome of chronic rotenone on energy status in relation to toxicity, however, is unknown. To examine this, mesencephalic cultures were exposed to chronic, low-dose rotenone (5-100 nM, 8 days in vitro) or acute, high-dose rotenone (500 nM, 1-24 h), and ATP/ADP levels and toxicity were measured. Chronic exposure to 5-50 nM rotenone produced selective dopamine cell loss. High-dose rotenone produced nonselective damage at all exposure times. Chronic, low-dose rotenone (37.5 nM) decreased ATP/ADP gradually over several days to 40% of controls, whereas high-dose rotenone (500 nM, 1-6 h), collapsed ATP/ADP by 1 h of exposure. The ubiquitin proteasomal pathway, an ATP-dependent pathway, is implicated in Parkinson's disease and, thus, various rotenone exposures were examined for effects on ubiquitin proteasomal function. Chronic, low-dose rotenone (25-50 nM, 8 days), but not acute, high-dose rotenone (500 nM, 1-6 h), caused accumulation of ubiquitinated proteins, E1-ubiquitin activation, and increased proteasomal activities prior to toxicity even though both exposures increased free radical production. Findings show that selective dopamine cell loss and alterations in ubiquitin proteasomal function only occur with rotenone exposures that partially maintain ATP/ADP. High concentrations of rotenone that collapse energy status kill neurons in a nonselective manner independent of the ubiquitin proteasomal pathway.

Sleep disturbances in the rotenone animal model of Parkinson disease

Parkinson disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc) and the presence of intracytoplasmatic inclusions known as Lewy bodies. Chronic administration of rotenone (RT) produces Parkinson's-like symptoms in rats. Because PD patients have disrupted sleep patterns, we determined if chronic RT administration produces similar changes in rat sleep. RT was administered for 28 days to rats. Basal and vehicle (VH) rats received saline or dimethyl sulfoxide and polyethylene glycol (1:1), respectively. VH infusion induced a progressive decrease in non-rapid eye movement sleep (NREMS) during the 4-week period of VH infusion and REMS was reduced in the third and fourth week of VH infusion. VH infusion did not induce dopaminergic cell degeneration. Rats receiving RT infusion also showed decreased NREMS during the treatment. REMS was dramatically reduced on day 7 although subsequently on days 13 and 20 REMS was similar to basal values. After 4 weeks of RT infusion, time in REMS was decreased again. In RT-treated rats, progressive dopaminergic cell degeneration occurred in the SNc. After 4 weeks of daily injections of l-dopa in RT-infused rats, NREMS values remained similar to those values obtained after RT alone. l-dopa therapy did, however, induce a recovery of REMS in weeks 3 and 4 of RT infusion. Dopaminergic cell damage persisted in the l-dopa-RT-infused rats. We conclude that the RT-PD rat model is associated with large long-term sleep disruption, however, the vehicle, DMSO/PEG had as large an effect as RT on sleep, thus changes in sleep cannot be ascribed to loss of dopaminergic cells. Such results question the validity of the RT-PD rat model.

Increased sensitivity of striatal dopamine release to H 2O 2 upon chronic rotenone treatment

It is believed that both mitochondrial dysfunction and oxidative stress play important roles in the pathogenesis of Parkinson's disease (PD). We studied the effect of chronic systemic exposure to the mitochondrial inhibitor rotenone on the uptake, content, and release of striatal neurotransmitters upon neuronal activity and oxidative stress, the latter simulated by H 2O 2 perfusion. The dopamine content in the rat striatum is decreased simultaneously with the progressive loss of tyrosine hydroxylase (TH) immunoreactivity in response to chronic intravenous rotenone infusion. However, surviving dopaminergic neurons take up and release only a slightly lower amount of dopamine (DA) in response to electrical stimulation. Striatal dopaminergic neurons showed increased susceptibility to oxidative stress by H 2O 2, responding with enhanced release of DA and with formation of an unidentified metabolite, which is most likely the toxic dopamine quinone (DAQ). In contrast, the uptake of [ 3H]choline and the electrically induced release of acetylcholine increased, in coincidence with a decline in its D 2 receptor-mediated dopaminergic control. Thus, oxidative stress-induced dysregulation of DA release/uptake based on a mitochondrial deficit might underlie the selective vulnerability of dopaminergic transmission in PD, causing a self-amplifying production of reactive oxygen species, and thereby contributing to the progressive degeneration of dopaminergic neurons.