Modulators of metabotropic glutamate receptor subtype 5 (mGluR5) may provide novel treatments for multiple central nervous system (CNS) disorders, including anxiety and schizophrenia. Although compounds have been developed to better understand the physiological roles of mGluR5 and potential usefulness for the treatment of these disorders, there are limitations in the tools available, including poor selectivity, low potency, and limited solubility. To address these issues, we developed an innovative assay that allows simultaneous screening for mGluR5 agonists, antagonists, and potentiators. We identified multiple scaffolds that possess diverse modes of activity at mGluR5, including both positive and negative allosteric modulators (PAMs and NAMs, respectively). 3-Fluoro-5-(3-(pyridine-2-yl)-1,2,4-oxadiazol-5-yl)benzonitrile (VU0285683) was developed as a novel selective mGluR5 NAM with high affinity for the 2-methyl-6-(phenylethynyl)-pyridine (MPEP) binding site. VU0285683 had anxiolytic-like activity in two rodent models for anxiety but did not potentiate phencyclidine-induced hyperlocomotor activity. (4-Hydroxypiperidin-1-yl)(4-phenylethynyl)phenyl)methanone (VU0092273) was identified as a novel mGluR5 PAM that also binds to the MPEP site. VU0092273 was chemically optimized to an orally active analog, N-cyclobutyl-6-((3-fluorophenyl)ethynyl)nicotinamide hydrochloride (VU0360172), which is selective for mGluR5. This novel mGluR5 PAM produced a dose-dependent reversal of amphetamine-induced hyperlocomotion, a rodent model predictive of antipsychotic activity. Discovery of structurally and functionally diverse allosteric modulators of mGluR5 that demonstrate in vivo efficacy in rodent models of anxiety and antipsychotic activity provide further support for the tremendous diversity of chemical scaffolds and modes of efficacy of mGluR5 ligands. In addition, these studies provide strong support for the hypothesis that multiple structurally distinct mGluR5 modulators have robust activity in animal models that predict efficacy in the treatment of CNS disorders.

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Understanding thrombosis is critical for effective treatment of patients at risk for heart attack and stroke. Simultaneous activation of the Gq‐coupled P2Y1 receptor and the Gi‐coupled P2Y12 receptor is required for ADP‐promoted platelet aggregation— deletion or inhibition of either receptor results in the loss of ADP‐induced aggregation. Unlike the P2Y12 receptor, the P2Y1 receptor in both mouse and human platelets undergoes profound and rapid desensitization in response to sub‐aggregating levels of ADP. We hypothesize that this rapid inactivation is specific to the P2Y1 receptor and is physiologically relevant for proper regulation of platelet hemostasis. To test the specificity of desensitization, we compared the rate of desensitization after agonist addition of the 5HT2A and TxA2 receptors, which are also Gq‐coupled, to that of the P2Y1 receptor. These data reveal that only the P2Y1 receptor rapidly desensitizes in response to its cognate agonist. To determine the residue(s) responsible for P2Y1 desensitization, we transplanted retrovirally infected bone marrow cells expressing P2Y1 receptor Ser/Thr mutants into P2Y1−/− mice to examine the desensitization of the P2Y1 receptor ex vivo. These mice will also be used to examine the physiological consequences of expressing a non‐desensitizing P2Y1 receptor by measuring thrombus formation in vivo in response to arterial vessel wall injury.(Supported by NIH grant HL54889)