Low dose rotenone treatment causes selective transcriptional activation of cell death related pathways in dopaminergic neurons in vivo

Mitochondrial complex I inhibition has been implicated in the degeneration of midbrain dopaminergic (DA) neurons in Parkinson's disease. However, the mechanisms and pathways that determine the cellular fate of DA neurons downstream of the mitochondrial dysfunction have not been fully identified. We conducted cell-type specific gene array experiments with nigral DA neurons from rats treated with the complex I inhibitor, rotenone, at a dose that does not induce cell death. The genome wide screen identified transcriptional changes in multiple cell death related pathways that are indicative of a simultaneous activation of both degenerative and protective mechanisms. Quantitative PCR analyses of a subset of these genes in different neuronal populations of the basal ganglia revealed that some of the changes are specific for DA neurons, suggesting that these neurons are highly sensitive to rotenone. Our data provide insight into potentially defensive strategies of DA neurons against disease relevant insults.

Abnormal colonic motility in mice overexpressing human wild-type alpha-synuclein

The presynaptic protein alpha-synuclein (alphaSyn) has been implicated in both familial and sporadic forms of Parkinson's disease. We examined whether human alphaSyn-overexpressing mice under Thy1 promoter (Thy1-alphaSyn) display alterations of colonic function. Basal fecal output was decreased in Thy1-alphaSyn mice fed ad libitum. Fasted/refed Thy1-alphaSyn mice had a slower distal colonic transit than the wild-type mice, as monitored by 2.2-fold increase in time to expel an intracolonic bead and 2.9-fold higher colonic fecal content. By contrast, Thy1-alphaSyn mice had an increased fecal response to novelty stress and corticotropin releasing factor injected intraperipherally. These results indicate that Thy1-alphaSyn mice display altered basal and stress-stimulated propulsive colonic motility and will be a useful model to study gut dysfunction associated with Parkinson's disease.

Olfactory deficits in mice overexpressing human wildtype alpha-synuclein

Accumulation of alpha-synuclein in neurons of the central and peripheral nervous system is a hallmark of sporadic Parkinson's disease (PD) and mutations that increase alpha-synuclein levels cause familial PD. Transgenic mice overexpressing alpha-synuclein under the Thy1 promoter (Thy1-aSyn) have high levels of alpha-synuclein expression throughout the brain but no loss of nigrostriatal dopamine neurons up to 8 months, suggesting that they may be useful to model pre-clinical stages of PD. Olfactory dysfunction often precedes the onset of the cardinal motor symptoms of PD by several years and includes deficits in odor detection, discrimination and identification. In the present study, we measured olfactory function in 3- and 9-month-old male Thy1-aSyn mice with a buried pellet test based on latency to find an exposed or hidden odorant, a block test based on exposure to self and non-self odors, and a habituation/dishabituation test based on exposure to non-social odors. In a separate group of mice, alpha-synuclein immunoreactivity was assessed in the olfactory bulb. Compared with wildtype littermates, Thy1-aSyn mice could still detect and habituate to odors but showed olfactory impairments in aspects of all three testing paradigms. Thy1-aSyn mice also displayed proteinase K-resistant alpha-synuclein inclusions throughout the olfactory bulb. These data indicate that overexpression of alpha-synuclein is sufficient to cause olfactory deficits in mice similar to that observed in patients with PD. Furthermore, the buried pellet and block tests provided sufficient power for the detection of a 50% drug effect, indicating their usefulness for testing novel neuroprotective therapies.

Anatomical localization and regulation of somatostatin gene expression in the basal ganglia and its clinical implications

The distribution of somatostatin in both the human and rat brain suggests that it is involved in numerous functions, including endocrine regulation, cognition and memory, autonomic regulation and motor activity. We have examined the regulation of somatostatin mRNA in the striatum, a brain region involved in motor and cognitive behaviour. Somatostatin and its mRNA are expressed in this region in interneurons which are resistant to ischaemia, excitotoxicity and Huntington's disease, possibly because they express high levels of superoxide dismutase. Striatal somatostatin mRNA is increased by stimulation of NMDA (N-methyl-D-aspartate) receptors. Ischaemia-induced cortical lesions also increase somatostatin gene expression in the striatum. In contrast, the levels of striatal somatostatin mRNA decrease after treatment with haloperidol, an antipsychotic agent that produces extrapyramidal symptoms, but not clozapine, which does not. Further evidence for a role for striatal somatostatin in extrapyramidal symptoms includes the observation that somatostatin mRNA levels decrease in the striatum after lesions are made in the dopaminergic pathway, a feature of Parkinson's disease. The largest change in somatostatin gene expression after dopaminergic lesions is the increase in somatostatin mRNA level sin neurons of the internal pallidum and lateral hypothalamus projecting to the lateral habenula. The results suggest that changes in brain somatostatin gene expression occur in pathological conditions and may be related to their symptoms.

Effects of antioxidants on cancer prevention and neuromotor performance in Atm deficient mice

Ataxia telangiectasia (AT) is an autosomal recessive disorder characterized by immunodeficiency, neurodegeneration and cancer. The disease results from bi-allelic mutations in the AT mutated (ATM) gene involved in cell cycle checkpoint control and repair of DNA double-strand breaks. Evidence has been accumulating that oxidative stress is associated with AT and may be involved in the pathogenesis of the disease. This led to a hypothesis that antioxidants may alleviate the symptoms of AT. Consequently, several studies were conducted in Atm deficient mice to examine the role of antioxidants in cancer prevention and/or correction of neuromotor performance. N-acetyl-l-cysteine (NAC), EUK-189, tempol, and 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO) have been tested in Atm deficient mice. In contrast to other antioxidants, NAC has been used in the clinical practice for many decades and is available as a dietary supplement. In this article, we review chemoprevention studies in Atm deficient mice and, in more detail, our findings on the effect of NAC. Our short-term study showed that NAC suppressed genome rearrangements linked to cancer. The long-term study demonstrated that NAC reduced the incidence and multiplicity of lymphoma and improved some aspects of motor performance.

Behavioral phenotypes and pharmacology in genetic mouse models of Parkinsonism

Prior to the discovery of genes associated with familial forms of Parkinson's disease, animal models of Parkinson's disease mainly consisted of toxin models based exclusively on the degeneration of nigrostriatal dopamine neurons. These traditional models have provided valuable insight into symptomatic treatments for Parkinson's disease; however, they lack the broad extra-nigral pathology and the progression that is observed in the disease. The novel genetic mouse models recently generated are advantageous because they have mutations that are known to cause familial Parkinson's disease and thus they have good construct validity. To maximize the utility of these models, a thoughtful phenotypical characterization is important. Our laboratory has assembled a battery of behavioral tests to assess sensorimotor function in genetic mouse models of Parkinsonism. This review discusses the sensitivity of these tests in different genetic mice in addition to their behavioral response to dopamine agonists.

Development of striatal fast-spiking GABAergic interneurons

Fast-spiking GABAergic interneurons represent a very small portion of striatal neurons, yet they play a critical role in modulating cortical input and mediating inhibition of striatal medium-sized spiny projection neurons. Considering their pivotal role in the adult striatum, it is of importance to determine when during development these neurons acquire their characteristic properties and function. In this review we describe recent work from our laboratories indicating that fast-spiking GABAergic interneurons are under stronger cortical control than efferent neurons at postnatal day 12 but mature considerably between postnatal days 12-19 in the rat striatum. During this time period, their molecular development is under the control of GABAergic and cholinergic mechanisms. Thus, fast-spiking interneurons are poised to influence striatal function and perhaps development during the postnatal period in rats, and their properties could be influenced by commonly used pharmacological agents during a protracted developmental window. These findings point to the need for future research to better understand the functional maturation of this critical population of striatal GABAergic neurons, and the consequences of abnormal maturation of these cells.

Region-specific sprouting of crossed corticofugal fibers after unilateral cortical lesions in adult mice

Long considered to be limited to early development or restricted adult brain regions in mammals, axonal sprouting of spared axons into denervated brain areas now appears more widespread in the adult mammalian brain. However, its extent and mechanisms remain poorly understood. In this study, we show that robust sprouting of corticofugal axons occurs in the dorsolateral striatum but not the red nucleus of adult mice after unilateral lesions of the sensorimotor cortex induced either by mechanical removal or by thermocoagulation of pial blood vessels. These results show that local factors are critical for axonal sprouting in adult brain. They also extend previous findings in rats to a species readily amenable to genetic analysis in order to elucidate the mechanisms of this effect.

Genetic mouse models of parkinsonism: strengths and limitations

Parkinson's disease (PD) is a progressive neurodegenerative disorder. Patients with PD display a combination of motor symptoms including resting tremor, rigidity, bradykinesia, and postural instability that worsen over time. These motor symptoms are related to the progressive loss of dopamine neurons in the substantia nigra pars compacta. PD patients also suffer from nonmotor symptoms that may precede the cardinal motor symptoms and that are likely related to pathology in other brain regions. Traditional toxin models of PD have focused on the nigrostriatal pathway and the loss of dopamine neurons in this region, and these models have been important in our understanding of PD and in the development of symptomatic treatments for the disease. However, they are limited in that they do not reproduce the full pathology and progression seen in PD, thus creating a need for better models. The recent discovery of specific genes causing familial forms of PD has contributed to the development of novel genetic mouse models of PD. This review discusses the validity, benefits, and limitations of these new models.

Functional and molecular development of striatal fast-spiking GABAergic interneurons and their cortical inputs

Despite their small number, fast-spiking (FS) GABAergic interneurons play a critical role in controlling striatal output by mediating cortical feed-forward inhibition of striatal medium-sized spiny (MS) projection neurons. We have examined the functional development of FS interneurons and their cortical inputs, and the expression of three of their molecular markers, in the dorsolateral rat striatum between postnatal days (P)12--14 and 19--23, the time of major corticostriatal synaptogenesis. FS interneurons were visualized with infrared differential interference contrast (IR-DIC) optics and examined with current-clamp recording in the presence of the GABA(A) receptor antagonist bicuculline methiodide. FS interneurons displayed action potentials at relatively high frequencies in response to depolarizing current pulses by P12, but developmental changes occurred in action potential and afterhyperpolarization duration and amplitude and input resistance between P12--14 and P19--23, as well as an increase in maximum firing frequency in response to depolarizing current pulses. Maturation in electrophysiological properties was paralleled by increases in Kv 3.1 and parvalbumin mRNA expression, while GAD-67 mRNA levels remained constant. Furthermore, FS interneurons in the younger age group responded to stimulation of cortical afferents with excitatory postsynaptic potentials (EPSPs) of higher amplitudes and received significantly more spontaneous depolarizing inputs than did MS neurons. Thus, FS interneurons are under frequent and continuous cortical influence by the end of the 2nd postnatal week, a time when corticostriatal synapses are sparse, suggesting that they may provide a major inhibitory influence in the striatum during the period of intense developmental maturation.

Early behavioral deficits in R6/2 mice suitable for use in preclinical drug testing

Huntington's disease (HD) is a neurodegenerative disorder caused by an elongated glutamine repeat in huntingtin. Improved understanding of the molecular effects of the mutation opens new avenues for treatment. High-throughput automated behavioral tests that produce well-defined markers of disease progression are necessary for in vivo drug screening. We have identified early behavioral deficits in tests of motor function that are amenable to cost effective automated analysis in a mouse model of HD. Running wheel activity and climbing behavior were reduced in R6/2 HD transgenics from as early as 4.5 weeks of age, at a time when rotarod performance and grip strength were still normal. Power calculations showed that the running wheel test was appropriate for efficient, high-throughput drug screening at this early age. Furthermore, the data extend the range of behavioral deficits observed in 1-month-old R6/2 mice, an age when synaptic dysfunction can already be detected in the striatum.

Mechanisms of subventricular zone expansion after focal cortical ischemic injury

The rodent subventricular zone (SVZ) contains neural precursor cells that divide and then die in place or migrate to the olfactory bulb through the rostral migratory stream (RMS) to become new neurons. Despite the normally tight control in cell numbers in this region in adults, previous work from our laboratory and others has shown that SVZ cell number increases after a variety of brain injuries. The relative contribution of changes in rostral migration, cell proliferation, and cell death to increased cell number is poorly understood. We examined these parameters after focal cortical ischemic lesions distal from the SVZ in adult rats. Stereological analysis revealed that cell numbers remain constant in the SVZ and RMS until 5 days postinjury but then rapidly expanded by 150,000 cells by day 7 in each region. Rostral migration of SVZ cells was unaffected by the injury. Both cell death and proliferation increased in the SVZ as early as day 5. However, these two mechanisms became uncoupled when cell number increased, indicating that a distant brain injury expands the SVZ by disrupting the balance between cell death and proliferation in this adult neurogenic zone.

Vascular changes in the subventricular zone after distal cortical lesions

One of the effects of cortical lesions is to produce cell proliferation in the subventricular zone (SVZ), a neurogenic zone of the adult brain distal from the lesion. The mechanisms of these effects are unknown. Recent evidence points to a relationship between the vasculature and neurogenesis both in vitro and in vivo. In the present study, we asked whether cortical lesions induced vascular modifications in the distal SVZ in vivo. Lesions of the frontoparietal cortex were produced by thermocoagulation of pial blood vessels, a method that leads to highly reproducible loss of all cortical layers, sparing the corpus callosum and underlying striatum. These lesions induced increased immunoreactivity for vascular endothelial growth factor (VEGF) around the walls of SVZ vessels, at a considerable distance from the lesion. Vascular permeability was markedly increased in both the SVZ and RMS by 3 days after the injury. A dramatic increase in endothelial proliferation was followed by expansion of the local SVZ vascular tree 7 days after the injury. This time course corresponded to the proliferative changes in the SVZ, and a tight correlation was observed between the number of blood vessels and the increase in SVZ cell number. The data demonstrate that thermocoagulatory cortical lesions induce distal vascular changes that could play a role in lesion-induced SVZ expansion.

Effect of neurturin on multipotent cells isolated from the adult skeletal muscle

Ligands of the glial cell line-derived neurotrophic factors (GDNF)-family are trophic factors for the development and survival of multiple cell types, however their effects on non-neuronal stem cells are unknown. We examined the action of neurturin on a candidate stem cell population isolated from adult skeletal muscles. When grown as spheres, these cells expressed mRNAs for GDNF, persephin, GFR-alpha2, GFR-alpha4 (neurturin receptor), and Ret. Exposure of these cells to neurturin significantly augmented cell numbers via increased cell proliferation. After addition of retinoic acid, the cells exited the cell cycle, developed thin processes, and became immunoreactive for betaIII-tubulin, while Ret mRNA expression decreased, without changes in the level of GFR-alpha2 mRNA. Neurturin induced an outgrowth of processes on these betaIII-tubulin positive cells. Neurturin may therefore be beneficial in the use of these multipotent cells isolated from adult muscles for autologous transplants in neurological applications.

Migration and fate of newly born cells after focal cortical ischemia in adult rats

Neural cell migration and differentiation may participate in neural repair after adult brain injury; however, the survival and differentiation of newly born cells after different brain lesions are poorly understood. We have examined the migration and fate of bromodeoxyuridine (BrdU)-labeled cells after a highly reproducible focal ischemic lesion restricted to the frontoparietal cortex in adult rats. Thermocoagulation of pial blood vessels induces a circumscribed degeneration of all cortical layers while sparing the corpus callosum and striatum and increases cell proliferation in the subventricular zone (SVZ) and rostral migratory stream (RMS) within 7 days. We now show that, although the rostral migration of the newly born SVZ cells and their differentiation into neurons in the olfactory bulb were not affected by the lesion, numerous cells expressing the neuroblast marker doublecortin migrated laterally in the striatum and corpus callosum 5 days postinjury. In addition to the SVZ, BrdU-labeled cells were seen in the striatum, in the corpus callosum, and around the lesion. One month later, BrdU-labeled cells in the corpus callosum expressed transferrin and the pi isoform of glutathione-S-transferase (GST-pi), markers of oligodendrocytes. Other BrdU+ cells expressed a marker of astrocytes, but none expressed neuronal markers, suggesting that new neurons do not form or survive under these conditions. Numerous BrdU-labeled cells were still observed in the SVZ and RMS. The data show that focal cortical ischemia does not lead to the long-term survival of new neurons in the striatum or cortex but induces long-term alterations in the SVZ and the production of new oligodendrocytes that may contribute to neural repair.

Effect of GABA(A) receptor stimulation in the subthalamic nucleus on motor deficits induced by nigrostriatal lesions in the rat

Inhibition of the subthalamic nucleus by lesions or GABAergic agonists improves motor symptoms in monkeys or humans with a loss of nigrostriatal dopaminergic neurons, a characteristic of Parkinson's disease. In rats, nigrostriatal lesions induce deficits in a variety of motor tests that are ameliorated by dopaminergic agonists. However, the validity of these tests to predict the beneficial effects of subthalamic inhibition is not known. We have examined the effects of an intrasubthalamic injection of the GABA(A) receptor agonist muscimol (0.1 microg/0.1 microL) in intact rats and in rats with a unilateral nigrostriatal lesion. Muscimol induced a mild ipsiversive rotation in sham-operated (control) rats and blocked contraversive rotations induced by apomorphine in lesioned rats. In addition, in the cylinder test of limb use asymmetry, muscimol decreased the ipsilateral bias after lesion without inducing any significant effect in sham-operated controls. In the forced-step test, however, 0.1 microg (but not 0.01 microg) of muscimol into the subthalamic nucleus induced a behavioral bias by markedly decreasing the number of adjusting steps of the contralateral limb in control rats, similar to the effect of a nigrostriatal lesion. Neither dose improved performance in this test in rats with lesions, and the higher dose exacerbated the deficit. The data support a beneficial role of stimulating subthalamic GABA(A) receptors for akinesia but also reveal negative behavioral effects of this treatment and suggest that the cylinder and forced-step tests measure different aspects of behavioral deficits after dopaminergic lesions.

Early and progressive sensorimotor anomalies in mice overexpressing wild-type human alpha-synuclein

Accumulation of alpha-synuclein in brain is a hallmark of synucleinopathies, neurodegenerative diseases that include Parkinson's disease. Mice overexpressing alpha-synuclein under the Thy-1 promoter (ASO) show abnormal accumulation of alpha-synuclein in cortical and subcortical regions of the brain, including the substantia nigra. We examined the motor deficits in ASO mice with a battery of sensorimotor tests that are sensitive to alterations in the nigrostriatal dopaminergic system. Male wild-type and ASO mice were tested every 2 months for 8 months for motor performance and coordination on a challenging beam, inverted grid, and pole, sensorimotor deficits in an adhesive removal test, spontaneous activity in a cylinder, and gait. Fine motor skills were assessed by the ability to grasp cotton from a bin. ASO mice displayed significant impairments in motor performance and coordination and a reduction in spontaneous activity as early as 2 months of age. Motor performance and coordination impairments became progressively worse with age and sensorimotor deficits appeared at 6 months. Fine motor skills were altered at 4 months and worsened at 8 months. These data indicate that overexpression of alpha-synuclein induced an early and progressive behavioral phenotype that can be detected in multiple tests of sensorimotor function. These behavioral deficits provide a useful way to assess novel drug therapy in genetic models of synucleinopathies.

Transplantation of multipotent cells extracted from adult skeletal muscles into the subventricular zone of adult rats

Stem cells isolated from adult tissues may be useful for autologous cell therapy in the nervous system. In the present study we tested the ability of multipotent stem cells isolated from adult muscle to survive and respond to migratory and differentiating cues when transplanted into the adult subventricular zone (SVZ). Prior to transplantation the cells were grown as spheres that expressed doublecortin, nestin, and betaIII-tubulin, as well as the mRNAs for the receptor EphA4 and the ligands ephrin B1, ephrin B2, but not ephrin B3. Four weeks after transplantation into the anterior part of the SVZ in adult rats, surviving cells were observed along the ventricular wall, in the SVZ, and in the posterior rostral migratory stream (RMS). None of these cells stained for betaIII-tubulin or doublecortin, which are molecules expressed by migrating neuroblasts, and none were present in the more rostral regions of the RMS or the olfactory bulb. However, most surviving transplanted cells were integrated into the wall of the lateral ventricle and expressed vimentin, a marker also expressed by ependymocytes. No tumors were observed 4 weeks posttransplantation. Our results suggest that multipotent stem cells isolated from adult muscle, which can be easily and safely isolated from patients and rapidly expanded ex vivo, may provide autologous vectors for the local delivery of secreted factors to the ventricles or nearby regions.

Alpha-synuclein and transgenic mouse models

Identified as the cause of some familial forms of Parkinson disease (PD) and as one of the major component of Lewy bodies, alpha-synuclein (alpha-syn) became the molecular hallmark of several neurodegenerative conditions now designated as synucleinopathies. Transgenic models have been generated to elucidate its physiological and pathologic roles. Although none of the lines created display dopaminergic neuronal death in the substantia nigra, the models recapitulate some features of synucleinopathies and are useful to study the potential pathogenic role of alpha-synuclein and its molecular partners. This review describes the different alpha-synuclein transgenic models, their clinical relevance to synucleinopathies, and their further utilization to understand the disease process.

Genetic mouse models of Huntington's and Parkinson's diseases: illuminating but imperfect

Genetic mouse models based on identification of genes that cause Huntington's and Parkinson's diseases have revolutionized understanding of the mechanistic pathophysiological progression of these disorders. These models allow the earliest manifestations of the diseases to be identified, and they display behavioral, neuropathological and electrophysiological deficits that can be followed over time in mechanistic and drug studies. An intriguing feature is that they do not reproduce the relatively selective and massive cell loss characterizing the human diseases. There is more information on Huntington's disease models because the disorder involves a single gene that was identified over ten years ago; genetic mutations causing Parkinson's disease are rare and were discovered more recently, and models of the disease have been generated only within the past few years.

Behavioral and immunohistochemical effects of chronic intravenous and subcutaneous infusions of varying doses of rotenone

Mitochondrial toxins such as the complex 1 inhibitor rotenone are widely used as pesticides and may be present in military environments. Administration of rotenone can induce biochemical and histological alterations similar to those of Parkinson's disease in rats. However, only a subset of animals show these effects and it is unclear whether more subtle alterations are caused by chronic administration of rotenone in those animals that appear resistant to its toxic effects on dopaminergic nerve terminals. To address this question, vehicle or rotenone (2.0, 2.5, or 3.5 mg/kg/day) was administered intravenously or subcutaneously for 21 days to adult rats, and rotenone effects on survival, motor behavior, and striatal tyrosine hydroxylase immunoreactivity (TH-IR) were examined. Both intravenous and subcutaneous rotenone induced a dose-dependent decrease in survival rates. Surviving animals showed a decrease in spontaneous rearing. Locomotor activity and movement initiation time were also altered in some of the experimental groups. Confirming previous results, TH-IR in the striatum was markedly decreased in rats that fell ill early in the study and in a few of the surviving rats with high rotenone doses. However, none of the surviving rats receiving 2.0 mg/kg/day showed TH-IR loss reminiscent of Parkinson's disease, and loss of striatal TH-IR across doses was not correlated with motor behavior in individual rats. Thus, chronic administration of low doses of rotenone induces motor anomalies even in animals that do not develop histological signs of Parkinson's disease, indicating a pervasive neurological effect of moderate mitochondrial dysfunction in vivo.

Isolation and characterization of cells with neurogenic potential from adult skeletal muscle

Autologous cell therapies in neurodegenerative diseases and stroke will require an efficient generation of neuroprogenitors or neurons. We have previously shown that presumptive neural progenitors can be obtained from a candidate stem cell population isolated from adult skeletal muscle. Here we describe experimental conditions to isolate and characterize the cells with neurogenic potential from this population. Candidate stem cell population was isolated from adult skeletal muscle and expanded for selection during at least 30 cell divisions. FACS analysis revealed that this population was homogeneous with respect to CD45 (-), CD34 (-), and heterogeneous for CD90 (Thy-1) expression. The population was separated by cell sorting into three sub-populations based on CD90 expression (CD90-, CD90+, and CD90++) and each population expanded rapidly as free-floating spheres. When dissociated and plated in a neuronal differentiation medium, a large number of CD90+ cells acquired morphological characteristics of neuroprogenitors and neurons, and expressed markers of neurons but no markers of glial or muscle cells. In contrast, CD90- and CD90++ cells lacked this ability. Comparison of CD90+ and CD90- populations may be useful for studying the molecular characteristics defining the neuronal potential of stem cells from adult muscle. The selection of CD90+ expressing cells, combined with the growth conditions presented here, allows for rapid generation of a large number of cells which may be useful for autologous cell replacement therapies in the central nervous system.

Variable effects of chronic subcutaneous administration of rotenone on striatal histology

When infused in rats, rotenone, a mitochondrial complex I inhibitor, induces alterations that resemble the histological changes of Parkinson's disease, particularly degeneration of the nigrostriatal dopaminergic system. However, the specificity of rotenone effects has been challenged recently. We have re-examined the alterations caused by rotenone in the substantia nigra and the striatum of rats after infusion of rotenone (2 mg/kg per day s.c.) for 21 days. Three patterns of striatal tyrosine-hydroxylase immunoreactivity (TH-IR) were observed: 46% of animals showed no reduction, and 46% of animals showed diffuse reduction in TH-IR, whereas one animal presented a focal loss of TH-IR in the striatum. Confocal microscopy analysis showed that the vesicular monoamine transporter (VMAT2) was decreased in parallel with TH-IR, strongly suggesting a loss of striatal DA nerve terminals in animals with diffuse or central TH-IR loss. However, no significant loss of TH-IR neurons was observed in the substantia nigra. Analysis of NeuN and DARPP-32 immunoreactivity, and Nissl staining, in the striatum showed no striatal neuronal loss in animals with either preserved TH-IR or diffuse TH-IR reduction. However, in the animal with focal TH-IR loss, severe neuronal loss was evident in the center and the periphery of the striatum, together with microglial activation detected by OX-6 and OX-42 staining. Thus, in most cases, chronic subcutaneous infusion of low doses of rotenone does not induce significant striatal neuronal loss, despite TH-IR and VMAT-IR reduction in a subset of animals, supporting the use of rotenone as a model of Parkinson's disease under carefully controlled experimental conditions.

Development and anatomic localization of torsinA

We have mapped the distribution of torsinA, the protein that is mutated in dystonia type 1 (DYT1), during postnatal development in rat brain. TorsinA was expressed in most brain regions at postnatal day 7, and its expression became more intense and widespread with age. The distribution of torsinA, however, showed marked age-dependent differences among regions of the cerebral cortex and hippocampus. Notably, large cholinergic interneurons of the striatum displayed intense torsin labeling between postnatal days 14 and 21, a period of intense synaptogenesis in this region.