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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, METHODS, RESULTS. Meshes: Animals, Baclofen, Behavior, Animal, Disease Models, Animal, Fragile X Mental Retardation Protein, Fragile X Syndrome, Frontal Lobe, GABA-B Receptor Agonists, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Protein Biosynthesis, Signal Transduction, Social Behavior, TOR Serine-Threonine Kinases.
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Does r-Baclofen reverse a Social Behavior Deficit and Elevated Protein Synthesis in a Mouse Model of Fragile X Syndrome? Context: Fragile X syndrome (FXS) is the most common known inherited form of intellectual disability and the single genomic cause of autism spectrum disorders. It is caused by the absence of a fragile X mental retardation gene (Fmr1) product, FMRP, an RNA-binding translation suppressor. Elevated rates of protein synthesis in the brain and an imbalance between synaptic signaling via glutamate and γ-aminobutyric acid (GABA) are both considered important in the pathogenesis of FXS. In a mouse model of FXS (Fmr1 knockout [KO]), treatment with R-baclofen reversed some behavioral and biochemical phenotypes. A remaining crucial question is whether R-baclofen is also able to reverse increased brain protein synthesis rates. To answer this question, we measured regional rates of cerebral protein synthesis in vivo with the L-[1-(14)C]leucine method in vehicle- and R-baclofen-treated wildtype and Fmr1 KO mice. We further probed signaling pathways involved in the regulation of protein synthesis. Acute R-baclofen administration corrected elevated protein synthesis and reduced deficits on a test of social behavior in adult Fmr1 KO mice. It also suppressed activity of the mammalian target of rapamycin pathway, particularly in synaptosome-enriched fractions, but it had no effect on extracellular-regulated kinase 1/2 activity. Ninety min after R-baclofen treatment, we observed an increase in metabotropic glutamate receptor 5 expression in the frontal cortex, a finding that may shed light on the tolerance observed in human studies with this drug.
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Our results suggest that treatment via activation of the GABA (GABA receptor subtype B) system warrants further study in patients with FXS. Final Decision: yes