Silverman JL, Smith DG, Rizzo SJ, Karras MN, Turner SM, Tolu SS, Bryce DK, Smith DL, Fonseca K, Ring RH, Crawley JN. Negative allosteric modulation of the mGluR5 receptor reduces repetitive behaviors and rescues social deficits in mouse models of autism. Sci Transl Med 4: 131-151

Laboratory of Behavioral Neuroscience, National Institute of Mental Health, Bethesda, MD 20892-3730, USA.
Science translational medicine (Impact Factor: 15.84). 04/2012; 4(131):131ra51. DOI: 10.1126/scitranslmed.3003501
Source: PubMed


Neurodevelopmental disorders such as autism and fragile X syndrome were long thought to be medically untreatable, on the assumption that brain dysfunctions were immutably hardwired before diagnosis. Recent revelations that many cases of autism are caused by mutations in genes that control the ongoing formation and maturation of synapses have challenged this dogma. Antagonists of metabotropic glutamate receptor subtype 5 (mGluR5), which modulate excitatory neurotransmission, are in clinical trials for fragile X syndrome, a major genetic cause of intellectual disabilities. About 30% of patients with fragile X syndrome meet the diagnostic criteria for autism. Reasoning by analogy, we considered the mGluR5 receptor as a potential target for intervention in autism. We used BTBR T+tf/J (BTBR) mice, an established model with robust behavioral phenotypes relevant to the three diagnostic behavioral symptoms of autism--unusual social interactions, impaired communication, and repetitive behaviors--to probe the efficacy of a selective negative allosteric modulator of the mGluR5 receptor, GRN-529. GRN-529 reduced repetitive behaviors in three cohorts of BTBR mice at doses that did not induce sedation in control assays of open field locomotion. In addition, the same nonsedating doses reduced the spontaneous stereotyped jumping that characterizes a second inbred strain of mice, C58/J. Further, GRN-529 partially reversed the striking lack of sociability in BTBR mice on some parameters of social approach and reciprocal social interactions. These findings raise the possibility that a single targeted pharmacological intervention may alleviate multiple diagnostic behavioral symptoms of autism.

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Available from: Daniel G Smith, Feb 02, 2015
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    • "Mechanistically, these mice show alterations in the corticostriatal pathway [24] [25] and overexpression of mGluR5 receptors [26]. Corticostriatal dysfunction is associated with ASD [27] and negative allosteric modulation of the mGluR5 receptors rescued social behavior in ASD models [28]. Together, these observations led us to test the hypothesis that alpha-synuclein overexpressing mice also exhibit deficits in social behavior. "
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    ABSTRACT: Background: Patients with Parkinson's disease (PD) may exhibit deficits in "Theory of Mind", the ability to read others' mental states and react appropriately, a prerequisite for successful social interaction. Alpha-synuclein overexpression is widely distributed in the brain of patients with sporadic PD, suggesting that it may contribute to the non-motor deficits observed in PD patients. Mice over-expressing human wild-type alpha-synuclein under the Thy1 promoter (Thy1-aSyn mice) have synaptic deficits in the frontostriatal pathway, low cortical acetylcholine, and high level of expression of mGluR5 receptors, which have all been implicated in social recognition deficits. Objective: To determine whether Thy1-aSyn mice present alterations in their response to social stimuli. Methods: We have submitted Thy1-aSyn mice to tests adapted from autism models. Results: At 7-8 month of age Thy1-aSyn mice explored their conspecifics significantly less than did wild-type littermates, without differences in exploration of inanimate objects, and pairs of Thy1-aSyn mice were involved in reciprocal interactions for a shorter duration than wild-type mice at this age. These deficits persisted when the test animal was enclosed in a beaker and were not present at 3-4 months of age despite the presence of olfactory deficits at that age, indicating that they were not solely caused by impairment in olfaction. Conclusion: Thy1-aSyn mice present progressive deficits in social recognition, supporting an association between alpha-synuclein overexpression and Theory of Mind deficits in PD and providing a useful model for identifying mechanisms and testing novel treatments for these deficits which impact patients and caretakers quality of life.
    Journal of Parkinson's Disease 01/2015; 5(3). DOI:10.3233/JPD-140503 · 1.91 Impact Factor
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    • "Recently, clinical trials with glutamate antagonists have been initiated, since they have been proved to be effective in rescuing social deficits and repetitive behaviors in selected animal models of autism (108). Also the presence of high levels of taurine in the Hip could be correlated to high levels of glutamate. "
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    ABSTRACT: Autism Spectrum Disorders (ASD) are neurodevelopmental disorders with multifactorial origin characterized by social communication deficits and the presence of repetitive behaviors/interests. Several studies showed an association between the reelin gene mutation and increased risk of ASD and a reduced reelin expression in some brain regions of ASD subjects, suggesting a role for reelin deficiency in ASD etiology. Reelin is a large extracellular matrix glycoprotein playing important roles during development of the central nervous system. To deeply investigate the role of reelin dysfunction as vulnerability factor in ASD, we assessed the behavioral, neurochemical, and brain morphological features of reeler male mice. We recently reported a genotype-dependent deviation in the ultrasonic vocal repertoire and a general delay in motor development of reeler pups. We now report that adult male heterozygous (Het) reeler mice did not show social behavior and communication deficits during male-female social interactions. Wildtype and Het mice showed a typical light/dark locomotor activity profile, with a peak during the central interval of the dark phase. However, when faced with a mild stressful stimulus (a saline injection) only Het mice showed an over response to stress. In addition to the behavioral studies, we conducted high performance liquid chromatography and magnetic resonance imaging and spectroscopy to investigate whether reelin mutation influences brain monoamine and metabolites levels in regions involved in ASD. Low levels of dopamine in cortex and high levels of glutamate and taurine in hippocampus were detected in Het mice, in line with clinical data collected on ASD children. Altogether, our data detected subtle but relevant neurochemical abnormalities in reeler mice supporting this mutant line, particularly male subjects, as a valid experimental model to estimate the contribution played by reelin deficiency in the global ASD neurobehavioral phenotype.
    Frontiers in Pediatrics 09/2014; 2:95. DOI:10.3389/fped.2014.00095
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    • "GRN-259, a selective negative allosteric modulator of the mGluR5 receptor, was tested in BTBR mice. GRN-529 reduced repetitive behaviors in three cohorts of BTBR mice and it attenuated social withdrawal with an associated increase in communication, providing overall improvement in behavioral conditions (17). Treatment with the two AMPAKINE compounds CX1837 and CX1739, agents active on AMPA receptors that enhance excitatory glutamatergic action, succeeded in recovering social impairment but it did not attenuate the high levels of repetitive self-grooming in BTBR (18). "
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    ABSTRACT: Current therapeutics in autism spectrum disorders (ASD) only treat the associated symptoms, without addressing core social dysfunctions. A paradigm shift in research of the pathogenesis of ASD, its synaptic abnormalities and altered signaling in multiple dynamic systems, have led to new experimental treatments for treating the core social abnormalities of ASD. NMDA antagonists, especially memantine, have been introduced in clinical trials addressing glutamatergic transmission in children and adolescents with ASD. GABAergic signaling has been targeted in trials using the GABAB receptor agonist arbaclofen for ASD patients with promising results. Oxytocin has been recognized as implicated in social development and affiliative behaviors. Preliminary findings from clinical trials using oxytocin in children with ASD show encouraging improvements in social cognition, but larger studies are needed. In two of the single gene disorders associated with ASD, Insulin Growth Factor (IGF-1) is a new treatment that has been tested in Rett syndrome and Phelan-McDermid syndrome (Chromosome 22 deletion syndrome). IGF-1 has been demonstrated to reverse the reduction in the number of excitatory synapses and the density of neurons that characterize these conditions in animal studies and it is being introduced as an experimental treatment. As a novel approach to verify treatment efficacy, neural processing modifications were recently evaluated by fMRI after a pivotal response training intervention. Another study of neural changes in response to treatment examined variations in EEG signaling in patients after an Early Start Denver Model (ESDM) intervention.
    Frontiers in Pediatrics 06/2014; 2:61. DOI:10.3389/fped.2014.00061
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