Genetic variation and pesticide exposure influence blood DNA methylation signatures in females with early-stage Parkinson's disease.

Although sex, genetics, and exposures can individually influence risk for sporadic Parkinson's disease (PD), the joint contributions of these factors to the epigenetic etiology of PD have not been comprehensively assessed. Here, we profiled sex-stratified genome-wide blood DNAm patterns, SNP genotype, and pesticide exposure in agricultural workers (71 early-stage PD cases, 147 controls) and explored replication in three independent samples of varying demographics (n = 218, 222, and 872). Using a region-based approach, we found more associations of blood DNAm with PD in females (69 regions) than in males (2 regions, Δßadj| ≥0.03, padj ≤ 0.05). For 48 regions in females, models including genotype or genotype and pesticide exposure substantially improved in explaining interindividual variation in DNAm (padj ≤ 0.05), and accounting for these variables decreased the estimated effect of PD on DNAm. The results suggested that genotype, and to a lesser degree, genotype-exposure interactions contributed to variation in PD-associated DNAm. Our findings should be further explored in larger study populations and in experimental systems, preferably with precise measures of exposure.

A randomized double-blind placebo-controlled trial of low-dose interleukin-2 in relapsing-remitting multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is associated with regulatory T cells (Tregs) insufficiency while low-dose interleukin-2 (IL2LD) activates Tregs and reduces disease activity in autoimmune diseases. METHODS: We aimed at addressing whether IL2LD improved Tregs from MS patients. MS-IL2 was a single-center double-blind phase-2 study. Thirty patients (mean [SD] age 36.8 years [8.3], 16 female) with relapsing-remitting MS with new MRI lesions within 6 months before inclusion were randomly assigned in a 1:1 ratio to placebo or IL-2 at 1 million IU, daily for 5 days and then fortnightly for 6 months. The primary endpoint was change in Tregs at day-5. RESULTS: Unlike previous trials of IL2LD in more than 20 different autoimmune diseases, Tregs were not expanded at day-5 in IL2LD group, but only at day-15 (median [IQR] fold change from baseline: 1.26 [1.21-1.33] in IL2LD group; 1.01 [0.95-1.05] in placebo group, p < 0.001). At day-5, however, Tregs had acquired an activated phenotype (fold change of CD25 expression in Tregs: 2.17 [1.70-3.55] in IL2LD versus 0.97 [0.86-1.28] in placebo group, p < 0.0001). Regulator/effector T cells ratio remained elevated throughout treatment period in the IL2LD group (p < 0.001). Number of new active brain lesions and of relapses tended to be reduced in IL2LD treated patients, but the difference did not reach significance in this trial not powered to detect clinical efficacy. CONCLUSION: The effect of IL2LD on Tregs in MS patients was modest and delayed, compared to other auto-immune diseases. This, together with findings that Tregs improve remyelination in MS models and recent reports of IL2LD efficacy in amyotrophic lateral sclerosis, warrants larger studies of IL2LD in MS, notably with increased dosages and/or modified modalities of administration. TRIAL REGISTRATION INFORMATION: ClinicalTrials.gov: NCT02424396; EU Clinical trials Register: 2014-000088-42.

Dopamine denervation in the functional territories of the striatum: a new MR and atlas-based 123I-FP-CIT SPECT quantification method.

Current quantification methods of 123I-FP-CIT SPECT rely on anatomical parcellation of the striatum. We propose here to implement a new method based on MRI segmentation and functional atlas of the basal ganglia (MR-ATLAS) that could provide a reliable quantification within the sensorimotor, associative, and limbic territories of the striatum. Patients with Parkinson's disease (PD), idiopathic rapid eye movement sleep behavioral disorder (iRBD), and healthy controls underwent 123I-FP-CIT SPECT, MRI, motor, and cognitive assessments. SPECT data were corrected for partial volume effects and registered to a functional atlas of the striatum to allow quantification in every functional region of the striatum (nucleus accumbens, limbic, associative, and sensorimotor parts of the striatum). The MR-ATLAS quantification method is proved to be reliable in every territory of the striatum. In addition, good correlations were found between cognitive dysexecutive tests and the binding within the functional (limbic) territories of the striatum using the MR-ATLAS method, slightly better than correlations found using the anatomical quantification method. This new MR-ATLAS method provides a robust and useful tool for studying the dopaminergic system in PD, particularly with respect to cognitive functions. It may also be relevant to further unravel the relationship between dopaminergic denervation and cognitive or behavioral symptoms.

Parkinson's disease polygenic risk score is not associated with impulse control disorders: A longitudinal study.

OBJECTIVE: To examine the relationship between a Parkinson's disease (PD) polygenic risk score (PRS) and impulse control disorders (ICDs) in PD. BACKGROUND: Genome wide association studies (GWAS) have brought forth a PRS associated with increased risk of PD and younger disease onset. ICDs are frequent adverse effects of dopaminergic drugs and are also more frequent in patients with younger disease onset. It is unknown whether ICDs and PD share genetic susceptibility. METHODS: We used data from a multicenter longitudinal cohort of PD patients with annual visits up to 6 years (DIG-PD). At each visit ICDs, defined as compulsive gambling, buying, eating, or sexual behavior were evaluated by movement disorders specialists. We genotyped DNAs using the Megachip assay (Illumina) and calculated a weighted PRS based on 90 SNPs associated with PD. We estimated the association between PRS and prevalence of ICDs at each visit using Poisson generalized estimating equations, adjusted for dopaminergic treatment and other known risk factors for ICDs. RESULTS: Of 403 patients, 185 developed ICDs. Patients with younger age at onset had a higher prevalence of ICDs (p < 0.001) as well as higher PRS values (p = 0.06). At baseline, there was no association between the PRS and ICDs (overall, p = 0.84). The prevalence of ICDs increased over time similarly across the quartiles of the PRS (overall, p = 0.88; DA users, p = 0.99). CONCLUSION: Despite younger disease onset being associated with both higher PRS and ICD prevalence, our findings are not in favor of common susceptibility genes for PD and ICDs.

The PINK1 kinase-driven ubiquitin ligase Parkin promotes mitochondrial protein import through the presequence pathway in living cells.

Most of over a thousand mitochondrial proteins are encoded by nuclear genes and must be imported from the cytosol. Little is known about the cytosolic events regulating mitochondrial protein import, partly due to the lack of appropriate tools for its assessment in living cells. We engineered an inducible biosensor for monitoring the main presequence-mediated import pathway with a quantitative, luminescence-based readout. This tool was used to explore the regulation of mitochondrial import by the PINK1 kinase-driven Parkin ubiquitin ligase, which is dysfunctional in autosomal recessive Parkinson's disease. We show that mitochondrial import was stimulated by Parkin, but not by disease-causing Parkin variants. This effect was dependent on Parkin activation by PINK1 and accompanied by an increase in the abundance of K11 ubiquitin chains on mitochondria and by ubiquitylation of subunits of the translocase of outer mitochondrial membrane. Mitochondrial import efficiency was abnormally low in cells from patients with PINK1- and PARK2-linked Parkinson's disease and was restored by phosphomimetic ubiquitin in cells with residual Parkin activity. Altogether, these findings uncover a role of ubiquitylation in mitochondrial import regulation and suggest that loss of this regulatory loop may underlie the pathophysiology of Parkinson's disease, providing novel opportunities for therapeutic intervention.

Impact of an adaptive program for cognitive and emotional deficits (ADACOG program) in multiple sclerosis patients with cognitive impairments.

BACKGROUND: Cognitive impairment is frequent in multiple sclerosis (MS), affecting approximately 40 to 70% of patients. We developed a psycho-educational program (ADACOG program) to allow patients to cope with cognitive deficits. The purpose of this exploratory study was to investigate the impact of the ADACOG program on subjective self-reported cognitive impairments, quality of life, anxiety, depression and self-esteem in MS patients. METHODS: ADACOG program is a psycho-educational program focusing on cognitive and emotional dysfunctions in MS consisting of three modules in small groups lasting two hours every two weeks. Forty-five MS patients with self-reported cognitive impairments and objective cognitive deficits were enrolled consecutively in two groups: (i) the ADACOG group (N=24) and (ii) the control group (N=21). Both groups of patients completed questionnaires evaluating self-reported cognitive impairments (Multiple Sclerosis Neuropsychological Screening Questionnaire), quality of life (Multiple Sclerosis Impact Scale), anxiety and depression (Hospital Anxiety and Depression Scale, HAD) and self-esteem (Rosenberg Scale) at inclusion (M0), one month later (M1) and seven months after inclusion (M7). The evolution of outcomes within ADACOG group and between both groups was analyzed. RESULTS: The analyses within the ADACOG group showed that patients reported better quality of life and fewer anxiety symptoms at M1 compared to M0 (respectively P=0.03 and P=0,04). Moreover, patients presented less subjective self-reported cognitive deficits at M7 compared to M0 (P=0.003). Score evolution for HAD depression and self-esteem were not significant within the ADACOG group. The change M1-M0 for MSIS-29 and HAD anxiety scores was significantly different between both groups (respectively P=0.04 and P=0.008), with improvement of quality of life and anxiety in the ADACOG group. The evolution of scores between groups was not significant for the other outcomes. DISCUSSION: This study showed a small effect of a psycho-educational program focusing on cognitive and emotional disorders in MS patients with subjective self-reported cognitive deficits and objective cognitive deficits. Interest of psycho-education focusing on cognition in MS patients is discussed.

A Precision Medicine Initiative for Alzheimer's disease: the road ahead to biomarker-guided integrative disease modeling.

After intense scientific exploration and more than a decade of failed trials, Alzheimer's disease (AD) remains a fatal global epidemic. A traditional research and drug development paradigm continues to target heterogeneous late-stage clinically phenotyped patients with single 'magic bullet' drugs. Here, we propose that it is time for a paradigm shift towards the implementation of precision medicine (PM) for enhanced risk screening, detection, treatment, and prevention of AD. The overarching structure of how PM for AD can be achieved will be provided through the convergence of breakthrough technological advances, including big data science, systems biology, genomic sequencing, blood-based biomarkers, integrated disease modeling and P4 medicine. It is hypothesized that deconstructing AD into multiple genetic and biological subsets existing within this heterogeneous target population will provide an effective PM strategy for treating individual patients with the specific agent(s) that are likely to work best based on the specific individual biological make-up. The Alzheimer's Precision Medicine Initiative (APMI) is an international collaboration of leading interdisciplinary clinicians and scientists devoted towards the implementation of PM in Neurology, Psychiatry and Neuroscience. It is hypothesized that successful realization of PM in AD and other neurodegenerative diseases will result in breakthrough therapies, such as in oncology, with optimized safety profiles, better responder rates and treatment responses, particularly through biomarker-guided early preclinical disease-stage clinical trials.

"De-novo" consultation: Evaluation of an outpatient's clinic dedicated to early diagnosis of parkinsonian syndromes.

INTRODUCTION: In the absence of specific clinical signs, imaging or biomarkers, the differential diagnosis of degenerative parkinsonian syndromes may be difficult at early stages of the disease. To reduce the risk of misdiagnosis or delayed diagnosis and referral to multiple medical centers at disease onset, easier access to expert centers should be available. To improve the initial care of parkinsonian patients, the Parkinson's disease Expert Center (PEC) at Pitié-Salpêtrière Academic Hospital has set up a specific outpatients clinic with short waiting times dedicated to the diagnosis of early Parkinson's disease and related disorders. METHODS: The PEC setup first identifies requests for diagnostic confirmation of parkinsonian syndromes, then specific outpatients clinic visits are scheduled weekly, with examinations carried out by neurologists at the PEC on a rotating schedule. Data from the first year of the new procedure were analyzed retrospectively through self-administered questionnaires sent to patients seen during this period. The main outcomes were to confirm the ability to keep to short delays for patients' examinations and to assess patients' satisfaction with the setup. RESULTS: Both study outcomes were achieved. The creation of an outpatients clinic dedicated to the early diagnosis of parkinsonian syndromes allowed shorter delays before the first examination of 5 weeks instead of several months. Keeping to the weekly schedule and limited time taken for each visit was also achieved. Following this initial outpatients visit, diagnosis of a parkinsonian syndrome was clinically confirmed or further specified in 80% of cases. A survey of patients' satisfaction showed a rate of over 91% in terms of the timing and course of clinical examinations at our PEC. DISCUSSION/CONCLUSION: This study of our quality-improvement program for Parkinson's disease management has shown that specific consultations with shorter waiting times aiming to allow early specialized assessment of parkinsonian syndromes is beneficial for patients and reduces the risk of delayed diagnoses.

Inflammatory profile discriminates clinical subtypes in LRRK2-associated Parkinson's disease.

BACKGROUND AND PURPOSE: The presentation of Parkinson's disease patients with mutations in the LRRK2 gene (PDLRRK2 ) is highly variable, suggesting a strong influence of modifying factors. In this context, inflammation is a potential candidate inducing clinical subtypes. METHODS: An extensive battery of peripheral inflammatory markers was measured in human serum in a multicentre cohort of 142 PDLRRK2 patients from the MJFF LRRK2 Consortium, stratified by three different subtypes as recently proposed for idiopathic Parkinson's disease: diffuse/malignant, intermediate and mainly pure motor. RESULTS: Patients classified as diffuse/malignant presented with the highest levels of the pro-inflammatory proteins interleukin 8 (IL-8), monocyte chemotactic protein 1 (MCP-1) and macrophage inflammatory protein 1-ß (MIP-1-ß) paralleled by high levels of the neurotrophic protein brain-derived neurotrophic factor (BDNF). It was also possible to distinguish the clinical subtypes based on their inflammatory profile by using discriminant and area under the receiver operating characteristic curve analysis. CONCLUSIONS: Inflammation seems to be associated with the presence of a specific clinical subtype in PDLRRK2 that is characterized by a broad and more severely affected spectrum of motor and non-motor symptoms. The pro-inflammatory metabolites IL-8, MCP-1 and MIP-1-ß as well as BDNF are interesting candidates to be included in biomarker panels that aim to differentiate subtypes in PDLRRK2 and predict progression.

French consensus procedure for assessing cognitive function in Parkinson's disease.

INTRODUCTION: One of the objectives of the French expert centers for Parkinson's disease (NS-Park) network was to determine a consensus procedure for assessing cognitive function in patients with Parkinson's. This article presents this procedure and briefly describes the selected tests. METHODS: A group of 13 experts used the Delphi method for consensus building to define the overall structure and components of the assessment procedure. For inclusion in the battery, tests had to be validated in the French language, require little motor participation, have normative data and be recognized by the international community. Experimental tasks and tests requiring specific devices were excluded. RESULTS: Two possibilities were identified, depending on whether an abbreviated or comprehensive assessment of cognitive function was necessary. For an abbreviated assessment, the experts recommended the Montreal Cognitive Assessment (MoCA) as a screening test for cognitive impairment or dementia. For a comprehensive neuropsychological assessment, the experts recommended assessing global efficiency plus the five main cognitive domains (attention and working memory, executive function, episodic memory, visuospatial function and language) that may be impaired in Parkinson's disease, using two tests for each domain. DISCUSSION AND CONCLUSION: A common procedure for assessing cognitive function is now available across the French network dedicated to Parkinson's disease, and is recommended for both research and clinical practice. It will also help to promote standardization of the neuropsychological assessment of Parkinson's disease.

Clinical implications of neuropharmacogenetics.

INTRODUCTION: Pharmacogenetics aims to identify the underlying genetic factors participating in the variability of drug response. Indeed, genetic variability at the DNA or RNA levels can directly or indirectly modify the pharmacokinetic or the pharmacodynamic parameters of a drug. The ultimate aim of pharmacogenetics is to move towards a personalised medicine by predicting responders and non-responders, adjusting the dose of the treatment, and identifying individuals at risk of adverse drug effects. METHODS: A literature research was performed in which we reviewed all pharmacogenetic studies in neurological disorders including neurodegenerative diseases, multiple sclerosis, stroke and epilepsy. RESULTS: Several pharmacogenetic studies have been performed in neurology, bringing insights into the inter-individual drug response variability and in the pathophysiology of neurological diseases. The principal implications of these studies for the management of patients in clinical practice are discussed. CONCLUSION/DISCUSSION: Although several genetic factors have been identified in the modification of drug response in neurological disorders, most of them have a marginal predictive effect at the single gene level, suggesting mutagenic interactions as well as other factors related to drug interaction and disease subtypes. Most pharmacogenetic studies deserve further replication in independent populations and, ideally, in pharmacogenetic clinical trials to demonstrate their relevance in clinical practice.

Broca's area damage is necessary but not sufficient to induce after-effects of cathodal tDCS on the unaffected hemisphere in post-stroke aphasia.

BACKGROUND: The inter-individual variability of behavioral effects after tDCS applied to the unaffected right hemisphere in stroke may be related to factors such as the lesion location. OBJECTIVE/HYPOTHESIS: We investigated the effect of left Broca's area (BA) damage on picture naming in aphasic patients after cathodal tDCS applied over the right BA. METHODS: We conducted a study using pre-interventional diffusion and resting state functional MRI (rsfMRI) and two cross-over tDCS sessions (TYPE: sham and cathodal) over the right homologous BA in aphasic stroke patients with ischemic lesions involving the left BA (BA+) or other left brain areas (BA-). Picture naming accuracy was assessed after each session. Inter-hemispheric (IH) functional balance was investigated via rsfMRI connectivity maps using the right BA as a seed. Probabilistic tractography was used to study the integrity of language white matter pathways. RESULTS: tDCS had different effects on picture naming accuracy in BA+ and BA- patients (TYPE × GROUP interaction, F(1,19): 4.6, P: 0.04). All BA- patients except one did not respond to tDCS and demonstrated normal IH balance between the right and left BA when compared to healthy subjects. BA+ patients were improved by tDCS in 36% and had decreased level of functional IH balance. Improvement in picture naming after cathodal tDCS was associated with the integrity of the arcuate fasciculus in BA+ patients. CONCLUSIONS: Behavioral effects of cathodal tDCS on the unaffected right hemisphere differ depending on whether BA and the arcuate fasciculus are damaged. Therefore, IH imbalance could be a direct consequence of anatomical lesions.

Neuroprevention: a new challenge?

Neurodegenerative disease (NDD) has become the leading cause of disability and dependency in Western and European societies. Treatments, when available, are symptomatic, and their efficacy is usually poor or decreases with disease progression. So far, no treatment can effectively modify NDD, partly because of the inevitable delay between the onset of the pathological process and therapeutic intervention. The ideal strategy would be to stop the pathological process before neurons degenerate - in other words, before symptoms. However, to do this, the populations at high risk of developing NDD need to be identified. Predicting the appearance of NDD encounters two main issues. The first is to accurately determine the very beginning of the neurodegenerative process and to follow its course; the second is to determine those populations at high risk of developing NDD. Several approaches have been proposed to identify presymptomatic markers, including the refinement of the semiology in the early stages of the disease and/or the prospective follow-up of asymptomatic carriers of the genetic form of NDD in particular. To predict the onset of NDD at the asymptomatic stage, however, raises ethical issues at a time when no preventative medication is as yet available.

A novel DCC mutation and genetic heterogeneity in congenital mirror movements.

OBJECTIVE: DCC is the receptor for netrin, a protein that guides axon migration of developing neurons across the body's midline. Mutations in the DCC gene were recently identified in 2 families with congenital mirror movements (MM). The objective was to study clinical and genetic characteristics of 3 European families with MM and to test whether this disorder is genetically homogeneous. METHODS: We studied 3 MM families with a total of 13 affected subjects. Each patient had a standardized interview and neurologic examination, focusing on the phenomenology and course of the MM. The severity of MM was also assessed. Molecular analysis of DCC was performed in the index cases. In addition, linkage analysis of the DCC locus was performed in a large French family. RESULTS: The clinical expression and course of MM were very similar in all the affected subjects, regardless of DCC mutational status. However, slight intersubject variability in the severity of MM was noted within each family. Onset always occurred in infancy or early childhood, and MM did not deteriorate over time. Motor disability due to MM was mild and restricted to activities that require independent movements of the 2 hands. We found a novel mutation in the DCC gene in an Italian family with MM associated with abnormal ipsilateral corticospinal projection. The DCC locus was excluded in the French family. CONCLUSION: DCC has a crucial role in the development of corticospinal tracts in humans. Congenital MM is genetically heterogeneous, despite its clinical homogeneity.

Segmental progression of early untreated Parkinson's disease: a novel approach to clinical rating.

OBJECTIVE: To assess the ability of potentially neuroprotective compounds to slow the progression of Parkinson's disease (PD), sensitive rating scales are needed to detect clinically meaningful effects. The topographical progression of motor signs in early untreated PD was evaluated to complement current clinical ratings and enhance the sensitivity to detect disease progression. METHODS: 12 patients referred for diagnostic evaluation of untreated de novo PD underwent detailed clinical assessment of motor parkinsonian signs at baseline and after 6 and 12 months of follow-up using the Unified Parkinson's Disease Rating Scale, motor part (UPDRS-III), and a newly developed approach of detailed segmental rating taking into account the localisation of motor signs in all of the major joints and muscle groups in the body. The progression of PD, as measured with the UPDRS-III, was compared with the segmental ratings. RESULTS: UPDRS-III scores and segmental ratings for rigidity and rest and postural tremor, but not bradykinesia, progressed significantly during the observation period. Progression of normalised segmental ratings for rigidity and tremor was significantly larger than the UPDRS-III ratings over 1 year. The segmental ratings for rigidity and tremor as well as their combination with the UPDRS-III bradykinesia rating were more sensitive a measure for progression of PD than the UPDRS-III. CONCLUSIONS: Taking into account the segmental evolution of parkinsonian signs may be a useful adjunct to UPDRS-III evaluations to measure clinical disease progression of PD. If validated in subsequent larger cohorts, this may be useful in trials of neuroprotective agents.

[Role and regulation of dopamine D1 receptors in the striatum: implications for the genesis of dyskinesia in Parkinson's disease]. / Rôle et régulation du récepteur D1 de la dopamine dans le striatum: implications dans les dyskinésies de la maladie de Parkinson.

L-dopa treatment of Parkinson's disease is complicated in the long term by the appearance of dyskinesia. Hypersensitivity of D1 dopamine receptor has been suggested to play a role in these delayed adverse effects. Hypersensitivity of dopamine D1 receptor in Parkinson's disease can be accounted for by increased levels of Galphaolf, the stimulatory G protein which couples D1 receptor to adenylyl cyclase in the striatum. We here discuss the possible role of D1 receptor signal transduction in the genesis of L-dopa-induced dyskinesia in the light of Galphaolf regulation.

[Pergolide associated valvulopathy: critical analysis of the literature and practical recommendations]. / Valvulopathies sous pergolide: revue critique de la littérature et conduite à tenir en pratique.

INTRODUCTION: Pergolide is a widely used antiparkinsonian dopamine agonist. Following occasional case reports, two studies recently suggested potentially frequent and severe valvular disease associated with pergolide intake. STATE OF ART: Although there is now strong evidence to consider that pergolide may induce valvulopathy, incidence, severity, and risk factors for this adverse effect remain to be clarified. Valvular disease associated with pergolide consists in fibrosis and resembles conditions described in carcinoid carcinoma and in patients taking fenfluramine therapy. The mechanisms leading to valvular fibrosis are unknown but involvement of 5-HT(2B) receptors, especially expressed in valvular fibroblasts, is suspected. PERSPECTIVES AND CONCLUSIONS: Following the recommendations of the Agence Française de Sécurité Sanitaire des Produits de Santé, we describe a clinical practice attitude for pergolide therapy in Parkinson's disease.

Galpha(olf) levels are regulated by receptor usage and control dopamine and adenosine action in the striatum.

In the striatum, dopamine D(1) and adenosine A(2A) receptors stimulate the production of cAMP, which is involved in neuromodulation and long-lasting changes in gene expression and synaptic function. Positive coupling of receptors to adenylyl cyclase can be mediated through the ubiquitous GTP-binding protein Galpha(S) subunit or through the olfactory isoform, Galpha(olf), which predominates in the striatum. In this study, using double in situ hybridization, we show that virtually all striatal efferent neurons, identified by the expression of preproenkephalin A, substance P, or D(1) receptor mRNA, contained high amounts of Galpha(olf) mRNA and undetectable levels of Galpha(s) mRNA. In contrast, the large cholinergic interneurons contained both Galpha(olf) and Galpha(s) transcripts. To assess the functional relationship between dopamine or adenosine receptors and G-proteins, we examined G-protein levels in the striatum of D(1) and A(2A) receptor knock-out mice. A selective increase in Galpha(olf) protein was observed in these animals, without change in mRNA levels. Conversely, Galpha(olf) levels were decreased in animals lacking a functional dopamine transporter. These results indicate that Galpha(olf) protein levels are regulated through D(1) and A(2A) receptor usage. To determine the functional consequences of changes in Galpha(olf) levels, we used heterozygous Galpha(olf) knock-out mice, which possess half of the normal Galpha(olf) levels. In these animals, the locomotor effects of amphetamine and caffeine, two psychostimulant drugs that affect dopamine and adenosine signaling, respectively, were markedly reduced. Together, these results identify Galpha(olf) as a critical and regulated component of both dopamine and adenosine signaling.

Galpha(olf) is necessary for coupling D1 and A2a receptors to adenylyl cyclase in the striatum.

In the brain, dopamine and adenosine stimulate cyclic AMP (cAMP) production through D1 and A2a receptors, respectively. Using mutant mice deficient in the olfactory isoform of the stimulatory GTP-binding protein alpha subunit, Galpha(olf), we demonstrate here the obligatory role of this protein in the adenylyl cyclase responses to dopamine and adenosine in the caudate putamen. Responses to dopamine were also dramatically decreased in the nucleus accumbens but remained unaffected in the prefrontal cortex. Moreover, in the caudate putamen of mice heterozygous for the mutation, the amounts of Galpha(olf) were half of the normal levels, and the efficacy of dopamine- and CGS 21680 A(2) agonist-stimulated cAMP production was decreased. Together, these results identify Galpha(olf) as a critical parameter in the responses to dopamine and adenosine in the basal ganglia.

Involvement of the extracellular signal-regulated kinase cascade for cocaine-rewarding properties.

A central feature of drugs of abuse is to induce gene expression in discrete brain structures that are critically involved in behavioral responses related to addictive processes. Although extracellular signal-regulated kinase (ERK) has been implicated in several neurobiological processes, including neuronal plasticity, its role in drug addiction remains poorly understood. This study was designed to analyze the activation of ERK by cocaine, its involvement in cocaine-induced early and long-term behavioral effects, as well as in gene expression. We show, by immunocytochemistry, that acute cocaine administration activates ERK throughout the striatum, rapidly but transiently. This activation was blocked when SCH 23390 [a specific dopamine (DA)-D1 antagonist] but not raclopride (a DA-D2 antagonist) was injected before cocaine. Glutamate receptors of NMDA subtypes also participated in ERK activation, as shown after injection of the NMDA receptor antagonist MK 801. The systemic injection of SL327, a selective inhibitor of the ERK kinase MEK, before cocaine, abolished the cocaine-induced ERK activation and decreased cocaine-induced hyperlocomotion, indicating a role of this pathway in events underlying early behavioral responses. Moreover, the rewarding effects of cocaine were abolished by SL327 in the place-conditioning paradigm. Because SL327 antagonized cocaine-induced c-fos expression and Elk-1 hyperphosphorylation, we suggest that the ERK intracellular signaling cascade is also involved in the prime burst of gene expression underlying long-term behavioral changes induced by cocaine. Altogether, these results reveal a new mechanism to explain behavioral responses of cocaine related to its addictive properties.