Selective agonists of the M1 subtype of muscarinic acetylcholine receptor (mAChR) may provide a novel approach for treatment of both psychosis and cognitive disturbances in patients suffering from schizophrenia and other CNS disorders. Unfortunately, previous efforts to develop highly selective M1 receptor agonists have failed because of the high conservation of the orthosteric ACh binding site across all mAChR subtypes. We have now developed highly selective activators of the M1 receptor that have no activity at any other mAChR subtype. The key to achieving this unprecedented selectivity was to target allosteric sites on M1 rather than developing traditional agonists acting at the highly conserved ACh binding site. These novel M1 allosteric activators have excellent pharmacokinetic properties and brain penetration. Furthermore, preliminary studies suggest that representative compounds have efficacy in animal models that predict antipsychotic and cognition-enhancing effects. Interestingly, structurally distinct M1-selective allosteric activators can differentially regulate coupling of M1 to various signaling pathways. For instance, a compound termed BQCA increases M1 activation of phospholipase C (PLC), calcium mobilization, and recruitment of 2- arrestin proteins to the cell membrane. In contrast, two other M1 allosteric agonists, activate M1 coupling to PLC and calcium mobilization but do not induce 2-arrestin recruitment. In addition, our studies suggest that these agents may differentially regulate coupling of M1 to protein kinase pathways. These surprising findings suggest that distinct M1 allosteric activators could have fundamentally different effects on CNS function and could differ in their potential therapeutic utility. Thus, it will be critical to fully understand the effects of different M1-selective allosteric modulators on coupling of M1 to different signaling pathways and to determine how this relates to electrophysiological effects of these agents and effects in animal models that predict efficacy in treatment of different domains of schizophrenia. We will perform a series of studies in to systematically determine the effects of representative M1 allosteric activators on cell signaling and electrophysiological responses in forebrain neurons important for antipsychotic and cognition-enhancing effects of these agents. In addition, we will determine the behavioral effects of M1 allosteric activators in rodent models that predict antipsychotic and cognition-enhancing effects. These studies will allow us to rigorously test the hypothesis that selective allosteric activators of M1 have effects in animal models that predict efficacy as novel antipsychotic and cognition-enhancing agents. In addition, we will determine whether the electrophysiological and behavioral effects of specific M1 allosteric activators vary depending on the effects of the novel compounds on coupling of M1 to specific cell signaling pathways.

Public Health Relevance

Studies in patients suffering from the schizophrenia suggest that drugs that selectively activate a specific receptor for the neurotransmitter acetylcholine may provide a novel approach for treatment of this debilitating brain disorder. We have discovered new drug like molecules that selectively activate with this neurotransmitter receptor. Studies are proposed to test the hypothesis that these novel molecules have actions that predict efficacy in treatment of schizophrenia.

National Institute of Health (NIH)
National Institute of Mental Health (NIMH)
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Pathophysiological Basis of Mental Disorders and Addictions Study Section (PMDA)
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Brady, Linda S
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Vanderbilt University Medical Center
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