A Calorie-Restricted Ketogenic Diet Reduces Cerebral Cortex Vascularization in Prepubertal Rats.

The antiepileptic effect of ketogenic diets is acknowledged but its mechanism of action is poorly understood. The present work aimed to evaluate possible effects of a calorie-restricted ketogenic diet (CRKD) on brain growth and angiogenesis in normal prepubertal rats. Two groups of prepubertal rats were fed with a standard diet (group 1) or a CRKD (group 2) for ten weeks. Then, rats were sacrificed and the thickness for the following structures was evaluated by histology: (1) cerebral cortex, (2) deep cerebral white matter, and (3) substantia nigra. The capillary density was also evaluated within: (1) cerebral cortex, (2) dentate gyrus of the hippocampus, (3) periaqueductal grey matter, and (4) substantia nigra. The results showed a smaller thickness of all the areas examined and a reduced capillary density within the cerebral cortex in the CRKD-treated group compared to the control group. These findings suggest an association between reduced angiogenesis within the cerebral cortex and the antiepileptic effects of CRKD.

Signal Alteration of Substantia Nigra on 3.0T Susceptibility-weighted Imaging in Parkinson's Disease and Vascular Parkinsonism.

Recent researches have found that 7 Tesla SWI can detect the alteration of substantia nigra hyperintensity in Parkinson's disease (PD), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). The aim of this study was to investigate whether 3 Tesla SWI (3T SWI) can visualize anatomical alterations occurring in a hyperintense structure of the substantia nigra in PD and vascular parkinsonism (VP), and whether the evaluation of abnormal signal can be used as a factor in the differential diagnosis of PD and VP. Using 3 Tesla MRI, we evaluated 38 healthy subjects, 33 patients with PD and 34 patients with VP. Two blinded readers independently assessed the images. We found that the dorsolateral nigral hyperintensity was absent in 31 of 33 patients with PD and 15 of 34 patients with VP. The dorsolateral nigral hyperintensity was present in 19 of 34 patients with VP and 35 of 38 healthy controls. Group comparisons of absence of dorsolateral nigral hyperintensity revealed significant differences between the patients with PD and those with VP (P<0.001). The sensitivity of SWI for PD was 93.9% and the specificity was 92.1%. Visual assessment of dorsolateral nigral hyperintensity on high-field SWI scans may serve as a new simple diagnostic imaging marker for PD. And our study results indicate that 3T SWI can be used as a tool to identify PD and VP.

Distinct Contributions of Ventromedial and Dorsolateral Subregions of the Human Substantia Nigra to Appetitive and Aversive Learning.

The role of neurons in the substantia nigra (SN) and ventral tegmental area (VTA) of the midbrain in contributing to the elicitation of reward prediction errors during appetitive learning has been well established. Less is known about the differential contribution of these midbrain regions to appetitive versus aversive learning, especially in humans. Here we scanned human participants with high-resolution fMRI focused on the SN and VTA while they participated in a sequential Pavlovian conditioning paradigm involving an appetitive outcome (a pleasant juice), as well as an aversive outcome (an unpleasant bitter and salty flavor). We found a degree of regional specialization within the SN: Whereas a region of ventromedial SN correlated with a temporal difference reward prediction error during appetitive Pavlovian learning, a dorsolateral area correlated instead with an aversive expected value signal in response to the most distal cue, and to a reward prediction error in response to the most proximal cue to the aversive outcome. Furthermore, participants' affective reactions to both the appetitive and aversive conditioned stimuli more than 1 year after the fMRI experiment was conducted correlated with activation in the ventromedial and dorsolateral SN obtained during the experiment, respectively. These findings suggest that, whereas the human ventromedial SN contributes to long-term learning about rewards, the dorsolateral SN may be particularly important for long-term learning in aversive contexts. SIGNIFICANCE STATEMENT: The role of the substantia nigra (SN) and ventral tegmental area (VTA) in appetitive learning is well established, but less is known about their contribution to aversive compared with appetitive learning, especially in humans. We used high-resolution fMRI to measure activity in the SN and VTA while participants underwent higher-order Pavlovian learning. We found a regional specialization within the SN: a ventromedial area was selectively engaged during appetitive learning, and a dorsolateral area during aversive learning. Activity in these areas predicted affective reactions to appetitive and aversive conditioned stimuli over 1 year later. These findings suggest that, whereas the human ventromedial SN contributes to long-term learning about rewards, the dorsolateral SN may be particularly important for long-term learning in aversive contexts.

Mesenchymal stem cells stabilize the blood-brain barrier through regulation of astrocytes.

INTRODUCTION: The blood-brain barrier (BBB) protects the brain against potentially neurotoxic molecules in the circulation, and loss of its integrity may contribute to disease progression in neurodegenerative conditions. Recently, the active role of reactive astrocytes in BBB disruption has become evident in the inflamed brain. In the present study, we investigated whether mesenchymal stem cell (MSC) treatment might modulate reactive astrocytes and thus stabilize BBB integrity through vascular endothelial growth factor A (VEGF-A) signaling in inflammatory conditions. METHODS: For the inflamed brain, we injected LPS using a stereotaxic apparatus and MSCs were injected into the tail vein. At 6 hours and 7 days after LPS injection, we analyzed modulatory effects of MSCs on the change of BBB permeability through VEGF-A signaling using immunochemistry and western blot. To determine the effects of MSCs on VEGF-A-related signaling in cellular system, we had used endothelial cells treated with VEGF-A and co-cultured astrocyte and BV 2 cells treated with lipopolysaccharide (LPS) and then these cells were co-cultured with MSCs. RESULTS: In LPS-treated rats, MSCs restored Evans blue infiltration and the number of endothelial-barrier antigen (EBA) and P-glycoprotein (p-gp)-expressing cells, which were significantly altered in LPS-treated animals. Additionally, MSC administration following LPS treatment markedly increased the density of astrocytic filaments around vessels and reversed LPS-induced elevations in VEGF-A levels as well as endothelial nitric oxide synthase (eNOS)-dependent downregulation of tight junction proteins in the endothelium. Consequently, MSC treatment reduced neutrophil infiltration and enhanced survival of midbrain dopaminergic neurons in LPS-treated animals. In cellular system, MSC treatment led to a significant reversion of VEGF-A-induced eNOS and tight junction protein expression in endothelial cells, which led to increased EBA expressing cells. Additionally, MSC treatment significantly attenuated LPS-induced increased expressions of IL-1ß in microglia and VEGF-A in astrocytes with an increase in IL-10 levels. CONCLUSION: The present study indicated that MSCs may stabilize BBB permeability by modulating astrocytic endfeet and VEGF-A signaling, which may be relevant to the treatment of Parkinsonian diseases as a candidate for disease modifying therapeutics.

String Vessel Formation is Increased in the Brain of Parkinson Disease.

BACKGROUND: String vessels are collapsed basement membrane without endothelium and have no function in circulation. String vessel formation contributes to vascular degeneration in Alzheimer disease. By comparing to age-matched control cases we have recently reported endothelial degeneration in brain capillaries of human Parkinson disease (PD). OBJECTIVE: Current study evaluated changes of basement membrane of capillaries, string vessel formation and their association with astrocytes, blood-brain-barrier integrity and neuronal degeneration in PD. METHODS: Brain tissue from human cases of PD and age-matched controls was used. Immunohistochemical staining for collagen IV, GFAP, NeuN, tyrosine hydroxylase, fibrinogen and Factor VIII was evaluated by image analysis in the substantia nigra, caudate nucleus and middle frontal gyrus. RESULTS: While the basement-membrane-associated vessel density was similar between the two groups, the density of string vessels was significantly increased in the PD cases, particularly in the substantia nigra. Neuronal degeneration was found in all brain regions. Astrocytes and fibrinogen were increased in the caudate nuclei of PD cases compared with control cases. CONCLUSIONS: Endothelial degeneration and preservation of basement membrane result in an increase of string vessel formation in PD. The data may suggest a possible role for cerebral hypoperfusion in the neuronal degeneration characteristic of PD, which needs further investigation. Elevated astrocytosis in the caudate nucleus of PD cases could be associated with disruption of the blood-brain barrier in this brain region.

Effects of inflammation on hippocampus and substantia nigra responses to novelty in healthy human participants.

Humans are naturally inquisitive. This tendency is adaptive, aiding identification of potentially valuable novel outcomes. The dopaminergic substantia nigra (SN) is implicated in the drive to explore novel stimuli and situations. However, infection and inflammation inhibit the motivation to seek out novelty. This likely serves to limit exposure to uncertain, potentially detrimental outcomes when metabolic resources are limited. Nevertheless, the neural mechanisms through which inflammation constrains novelty seeking are poorly understood. We therefore scanned 16 healthy participants (6 male, mean 27.2±7.3 years), using fMRI, once following experimental inflammation (intramuscular (i.m.) typhoid vaccination) and once after placebo (i.m. saline), with the aim of characterizing effects of inflammation on neural processing of novel and familiar place, and face stimuli. We specifically tested the effects of inflammation on the hypothesized roles of SN and hippocampus in novelty processing. Typhoid vaccination evoked a nearly threefold increase in circulating pro-inflammatory cytokine (interleukin-6) levels 3 h after injection, indicating induction of mild systemic inflammation. Enhanced hippocampal responses to novel (compared with familiar) stimuli were observed following both vaccine and placebo, consistent with intact central novelty detection. However, the normal bilateral reactivity of SN to stimulus novelty was significantly attenuated following inflammation. Correspondingly, inflammation also markedly impaired novelty-related functional coupling between the SN and hippocampus. These data extend previous findings of SN sensitivity to mild inflammation associated with changes in psychomotor responding, and suggest that inflammation-induced blunting of SN responses to hippocampal novelty signals may represent a plausible mechanism through which inflammation impairs motivational responses to novelty.

Atorvastatin protects GABAergic and dopaminergic neurons in the nigrostriatal system in an experimental rat model of transient focal cerebral ischemia.

INTRODUCTION: Cerebral ischemia is the third leading cause of death and the primary cause of permanent disability worldwide. Atorvastatin is a promising drug with neuroprotective effects that may be useful for the treatment of stroke. However, the effects of atorvastatin on specific neuronal populations within the nigrostriatal system following cerebral ischemia are unknown. OBJECTIVE: To evaluate the effects of atorvastatin on dopaminergic and GABAergic neuronal populations in exofocal brain regions in a model of transient occlusion of the middle cerebral artery. MATERIALS AND METHODS: Twenty-eight male eight-week-old Wistar rats were used in this study. Both sham and ischemic rats were treated with atorvastatin (10 mg/kg) or carboxymethylcellulose (placebo) by gavage at 6, 24, 48 and 72 hours post-reperfusion. We analyzed the immunoreactivity of glutamic acid decarboxylase and tyrosine hydroxylase in the globus pallidus, caudate putamen and substantia nigra. RESULTS: We observed neurological damage and cell loss in the caudate putamen following ischemia. We also found an increase in tyrosine hydroxylase immunoreactivity in the medial globus pallidus and substantia nigra reticulata, as well as a decrease in glutamic acid decarboxylase immunoreactivity in the lateral globus pallidus in ischemic animals treated with a placebo. However, atorvastatin treatment was able to reverse these effects, significantly decreasing tyrosine hydroxylase levels in the medial globus pallidus and substantia nigra reticulata and significantly increasing glutamic acid decarboxylase levels in the lateral globus pallidus. CONCLUSION: Our data suggest that post-ischemia treatment with atorvastatin can have neuro-protective effects in exofocal regions far from the ischemic core by modulating the GABAergic and dopaminergic neuronal populations in the nigrostriatal system, which could be useful for preventing neurological disorders.

Atorvastatin protects GABAergic and dopaminergic neurons in the nigrostriatal system in an experimental rat model of transient focal cerebral ischemia / La atorvastatina protege las neuronas gabérgicas y dopaminérgicas del sistema nigroestriatal en un modelo experimental de isquemia cerebral focal transitoria en ratas

Introduction: Cerebral ischemia is the third leading cause of death and the primary cause of permanent disability worldwide. Atorvastatin is a promising drug with neuroprotective effects that may be useful for the treatment of stroke. However, the effects of atorvastatin on specific neuronal populations within the nigrostriatal system following cerebral ischemia are unknown. Objective: To evaluate the effects of atorvastatin on dopaminergic and GABAergic neuronal populations in exofocal brain regions in a model of transient occlusion of the middle cerebral artery. Materials and methods: Twenty-eight male eight-week-old Wistar rats were used in this study. Both sham and ischemic rats were treated with atorvastatin (10 mg/kg) or carboxymethylcellulose (placebo) by gavage at 6, 24, 48 and 72 hours post-reperfusion. We analyzed the immunoreactivity of glutamic acid decarboxylase and tyrosine hydroxylase in the globus pallidus, caudate putamen and substantia nigra. Results: We observed neurological damage and cell loss in the caudate putamen following ischemia. We also found an increase in tyrosine hydroxylase immunoreactivity in the medial globus pallidus and substantia nigra reticulata, as well as a decrease in glutamic acid decarboxylase immunoreactivity in the lateral globus pallidus in ischemic animals treated with a placebo. However, atorvastatin treatment was able to reverse these effects, significantly decreasing tyrosine hydroxylase levels in the medial globus pallidus and substantia nigra reticulata and significantly increasing glutamic acid decarboxylase levels in the lateral globus pallidus. Conclusion: Our data suggest that post-ischemia treatment with atorvastatin can have neuro-protective effects in exofocal regions far from the ischemic core by modulating the GABAergic and dopaminergic neuronal populations in the nigrostriatal system, which could be useful for preventing neurological disorders.

Introducción. La isquemia cerebral es la tercera causa de muerte y la primera de discapacidad permanente en el mundo. La atorvastatina es un fármaco neuroprotector prometedor para el tratamiento de la apoplejía; sin embargo, su acción sobre las poblaciones neuronales del sistema nigroestriatal después de la isquemia aún se desconoce. Objetivo. Evaluar el efecto de la atorvastatina sobre poblaciones gabérgicas y dopaminérgicas en regiones exofocales en un modelo de oclusión transitoria de la arteria cerebral media. Materiales y métodos. Se utilizaron 28 ratas Wistar macho de ocho semanas de edad. Los ejemplares con isquemia simulada y los ejemplares sometidos a isquemia fueron tratados con atorvastatina (10 mg/kg) y carboximetilcelulosa (placebo) administrados por medio de sonda a las 6, 24, 48 y 72 horas después de la reperfusión. Se analizó la inmunorreacción de la descarboxilasa del ácido glutámico y de la tirosina hidroxilasa en el globo pálido, el putamen caudado y la sustancia negra. Resultados. Los datos confirmaron el daño neurológico y la pérdida celular en el putamen caudado. Se incrementó la inmunorreacción de la tirosina hidroxilasa en el globo pálido medial y la sustancia negra pars reticulata , disminuyendo la inmunorreacción de la descarboxilasa del ácido glutámico en el globo pálido lateral de los animales isquémicos tratados con placebo; sin embargo, el tratamiento con atorvastatina pudo revertirla, lo que logró una disminución significativa de la tirosina hidroxilasa en el globo pálido medial y la sustancia negra pars reticulata y aumentando los niveles de descarboxilasa del ácido glutámico en el globo pálido lateral. Conclusión. Nuestros datos sugieren que la atorvastatina en el tratamiento posterior a la isquemia ejerce neuroprotección en las zonas exofocales, modulando las poblaciones neuronales gabérgicas y dopaminérgicas del sistema nigroestriatal, lo que podría prevenir trastornos neurológicos.

Substantia nigra activity level predicts trial-to-trial adjustments in cognitive control.

Effective adaptation to the demands of a changing environment requires flexible cognitive control. The medial and the lateral frontal cortices are involved in such control processes, putatively in close interplay with the BG. In particular, dopaminergic projections from the midbrain (i.e., from the substantia nigra [SN] and the ventral tegmental area) have been proposed to play a pivotal role in modulating the activity in these areas for cognitive control purposes. In that dopaminergic involvement has been strongly implicated in reinforcement learning, these ideas suggest functional links between reinforcement learning, where the outcome of actions shapes behavior over time, and cognitive control in a more general context, where no direct reward is involved. Here, we provide evidence from functional MRI in humans that activity in the SN predicts systematic subsequent trial-to-trial RT prolongations that are thought to reflect cognitive control in a stop-signal paradigm. In particular, variations in the activity level of the SN in one trial predicted the degree of RT prolongation on the subsequent trial, consistent with a modulating output signal from the SN being involved in enhancing cognitive control. This link between SN activity and subsequent behavioral adjustments lends support to theoretical accounts that propose dopaminergic control signals that shape behavior both in the presence and in the absence of direct reward. This SN-based modulatory mechanism is presumably mediated via a wider network that determines response speed in this task, including frontal and parietal control regions, along with the BG and the associated subthalamic nucleus.

Whole-brain susceptibility mapping at high field: a comparison of multiple- and single-orientation methods.

Optimisation and comparison of the performance of three different methods for calculating three-dimensional susceptibility maps of the whole brain from gradient-echo (phase and modulus) image data acquired at 7 T is described. The methods studied are a multiple-orientation method in which image data acquired with the head at several different angles to the main field are combined and two methods which use data acquired at a single orientation: the first of these is based on exclusion of some k-space data from the calculation (through thresholding of the dipolar field kernel), while the second incorporates a regularisation method that is based on using information from the modulus images. The methods were initially optimised via analysis of data from a phantom containing different compartments of known susceptibility. As part of this work, a novel high-pass filtering methodology was introduced to remove background fields from field maps based on phase data. The optimised methods were successfully applied to high-resolution (0.7 mm isotropic) whole-brain modulus and phase data acquired in vivo from five healthy male subjects, 25-30 years of age. The multiple-orientation method yielded high quality susceptibility maps, out-performing the single-orientation methods. Venous blood vessels as well as the substantia nigra and globus pallidus brain regions showed particularly high positive susceptibility offsets relative to surrounding tissue, consistent with high deoxyhemoglobin and non-heme iron content, respectively. To compare the performance of the different methods, regions of interest were drawn in deep grey matter structures and in cortical grey and white matter. The threshold-based approach was fast and simple to use, but underestimated susceptibility differences and showed significant artefacts due to noise amplification in difficult regions of k-space. The regularised single-orientation method yielded contrast dependent on the choice of spatial priors, but demonstrated the potential to yield susceptibility maps of a similar quality to those calculated using data acquired at multiple orientations to the field.

Signal change of the substantia nigra on diffusion-weighted imaging following striatal infarction.

Diffusion-weighted imaging can depict secondary signal changes of the substantia nigra in patients with ipsilateral striatal infarction. We report four patients who demonstrated obvious signal changes of the substantia nigra in the subacute phase of stroke. Embolic stroke was diagnosed in all of the cases, and none of the patients presented clinical deterioration in their course. Embolic mechanism might be more closely related to the secondary change of the substantia nigra than thrombosis. The relationship between secondary nigral degeneration and stroke etiology or between the nigral lesions and recanalization of the middle cerebral artery remains unclear.

Aging and sedentarism decrease vascularization and VEGF levels in the rat substantia nigra. Implications for Parkinson's disease.

It is not known if aging induces changes in nigral vascularization and nigral vascular endothelial growth factor (VEGF) levels similar to those previously reported for Parkinson's disease (PD). In this study nonexercised rats displayed age-dependent decreases in the density of nigral microvessels and VEGF mRNA expression, which were reversed by physical exercise. Such changes may enhance the vulnerability of dopaminergic neurons and the risk of developing PD, and may be reduced by exercise. Furthermore, the observed pattern is the opposite of that previously observed in PD, suggesting that the process underlying PD is not an accelerated age-dependent decline in the dopaminergic system.

Personality traits are differentially associated with patterns of reward and novelty processing in the human substantia nigra/ventral tegmental area.

BACKGROUND: The long-standing observation that the novelty-seeking personality trait is a predictor of drug use and other reinforcable risky behaviors raises the question as to how novelty and reward processing functionally interact in mesolimbic dopaminergic circuitry and how this interaction is modulated by the novelty-seeking personality trait. METHODS: Functional magnetic resonance imaging (fMRI) hemodynamic responses to novelty and reward (monetary incentive) from the substantia nigra/ventral tegmental area (SN/VTA), the nucleus accumbens (NAcc), and the hippocampus of 29 subjects were correlated with novelty-seeking scores. These correlations were compared with those obtained for scores of reward-dependence. The fMRI data were taken from two experiments in which the interaction of novelty and reward was manipulated as a within-subject variable, and long-term memory for the critical stimuli was assessed after 24 hours. RESULTS: Novelty-seeking was positively correlated with SN/VTA activation elicited by novel cues that did not predict reward, whereas reward-dependence was related to activations elicited by novel cues that predicted reward. The positive correlation between SN/VTA responses to novelty and novelty-seeking scores was accompanied by a negative correlation with reward-related SN/VTA activation and memory enhancement. CONCLUSIONS: SN/VTA responses to novelty and reward are differentially affected by personality traits of novelty-seeking and reward-dependence. Importantly, novelty-seekers were more responsive to novel cues in the absence of reward and needed less reward to boost their memory for novel cues. These observations strongly suggest that for novelty-seekers, the motivational value of novelty is not necessarily based on actual reward-predicting stimulus properties.

Self-amplification of nigral degeneration in Parkinson's disease: a hypothesis.

This review analyzes current evidence regarding possible mechanisms of nigral damage in idiopathic Parkinson's disease (iPD). In normal brain, a specific interplay among the blood-brain barrier (BBB), substantia nigra (SN), and locus coeruleus (LC) creates the condition for a self-accelerating damage to the SN. Three vicious circles involving SN-BBB, LC-SN-BBB, and histamine-BBB-SN interactions are described. In iPD, a self-accelerating loss of nigral cells can be triggered by brain hypoperfusion and by an increased blood histamine level. iPD-associated factors such as decreased CSF levels of substance P, somatostatin, and glutamate can aggravate the vicious-circle-induced damage to the SN.

Peripheral inflammation is associated with altered substantia nigra activity and psychomotor slowing in humans.

BACKGROUND: Systemic infections commonly cause sickness symptoms including psychomotor retardation. Inflammatory cytokines released during the innate immune response are implicated in the communication of peripheral inflammatory signals to the brain. METHODS: We used functional magnetic resonance brain imaging (fMRI) to investigate neural effects of peripheral inflammation following typhoid vaccination in 16 healthy men, using a double-blind, randomized, crossover-controlled design. RESULTS: Vaccination had no global effect on neurovascular coupling but markedly perturbed neural reactivity within substantia nigra during low-level visual stimulation. During a cognitive task, individuals in whom typhoid vaccination engendered higher levels of circulating interleukin-6 had significantly slower reaction time responses. Prolonged reaction times and larger interleukin-6 responses were associated with evoked neural activity within substantia nigra. CONCLUSIONS: Our findings provide mechanistic insights into the interaction between inflammation and neurocognitive performance, specifically implicating circulating cytokines and midbrain dopaminergic nuclei in mediating the psychomotor consequences of systemic infection.

Substantia nigra/ventral tegmental reward prediction error disruption in psychosis.

While dopamine systems have been implicated in the pathophysiology of schizophrenia and psychosis for many years, how dopamine dysfunction generates psychotic symptoms remains unknown. Recent theoretical interest has been directed at relating the known role of midbrain dopamine neurons in reinforcement learning, motivational salience and prediction error to explain the abnormal mental experience of psychosis. However, this theoretical model has yet to be explored empirically. To examine a link between psychotic experience, reward learning and dysfunction of the dopaminergic midbrain and associated target regions, we asked a group of first episode psychosis patients suffering from active positive symptoms and a group of healthy control participants to perform an instrumental reward conditioning experiment. We characterized neural responses using functional magnetic resonance imaging. We observed that patients with psychosis exhibit abnormal physiological responses associated with reward prediction error in the dopaminergic midbrain, striatum and limbic system, and we demonstrated subtle abnormalities in the ability of psychosis patients to discriminate between motivationally salient and neutral stimuli. This study provides the first evidence linking abnormal mesolimbic activity, reward learning and psychosis.

Vascular Parkinsonism: a case of lacunar infarction localized to mesencephalic substantia nigra.

An 80-year-old caucasian man with acute onset parkinsonism is reported here. Lower limbs were predominantly involved and he did not show remarkable improvement with dopaminergic therapy. His MRI investigation showed an isolated lesion on the right side of the mesencephalon, consistent the localization of substantia nigra. The association of acute onset parkinsonism and this radiological finding is very rare in the literature.

Changes in vascularization in substantia nigra pars compacta of monkeys rendered parkinsonian.

The degeneration of nigral dopaminergic neurons in Parkinson's disease is believed to be associated with a glial reaction and inflammatory changes. In turn, local factors may induce changes in vascularization and contribute to neuronal vulnerability. Among these factors, Vascular Endothelial Growth Factor (VEGF) is released in adults under pathological conditions and is thought to induce angiogenesis. In order to determine whether changes in brain vasculature are observed in the affected brain regions in parkinsonism, we quantitatively analysed the VEGF-expressing cells and blood vessels in the substantia nigra of monkeys rendered parkinsonian by MPTP injection and compared the results with those obtained in control monkeys. Using stereological methods, we observed an increase in the number of VEGF-expressing neurons and an increase of the number of blood vessels and their volume occupying the substantia nigra pars compacta of monkeys rendered parkinsonian by chronic MPTP intoxication. These changes in vascularization may therefore modify the neuronal availability of blood nutrients, blood cells or toxic substances and neuronal susceptibility to parkinsonism.

Insulin degrading enzyme is expressed in the human cerebrovascular endothelium and in cultured human cerebrovascular endothelial cells.

Insulin degrading enzyme (IDE) is found in the cytosol, peroxisomes and plasma membrane of many cells. Although it preferentially cleaves insulin it can also cleave many other small proteins with diverse sequences including the monomeric form of the amyloid beta peptide (A beta). In the brain, IDE has been reported to be expressed predominantly in neurons. In this study, IDE expression was detected in cultured human cerebrovascular endothelial cells. Using laser capture microdissection followed by PCR analysis, it was found that IDE mRNA is expressed in human brain blood vessels. Using immunofluorescence and multiphoton microscopy IDE was localized to the endothelium of the cerebrovascular blood vessels in human.