Novel allosteric agonists of M ₁ muscarinic acetylcholine receptors induce brain region-specific responses that correspond with behavioral effects in animal models

M ₁ muscarinic acetylcholine receptors (mAChRs) represent a viable target for treatment of multiple disorders of the central nervous system (CNS) including Alzheimer's disease and schizophrenia. The recent discovery of highly selective allosteric agonists of M ₁ receptors has provided a major breakthrough in developing a viable approach for the discovery of novel therapeutic agents that target these receptors. Here we describe the characterization of two novel M ₁ allosteric agonists, VU0357017 and VU0364572, that display profound differences in their efficacy in activating M ₁ coupling to different signaling pathways including Ca ²⁺ and β-arrestin responses. Interestingly, the ability of these agents to differentially activate coupling of M ₁ to specific signaling pathways leads to selective actions on some but not all M ₁-mediated responses in brain circuits. These novel M ₁ allosteric agonists induced robust electrophysiological effects in rat hippocampal slices, but showed lower efficacy in striatum and no measureable effects on M ₁-mediated responses in medial prefrontal cortical pyramidal cells in mice. Consistent with these actions, both M ₁ agonists enhanced acquisition of hippocampal-dependent cognitive function but did not reverse amphetamine-induced hyperlocomotion in rats. Together, these data reveal that M ₁ allosteric agonists can differentially regulate coupling of M ₁ to different signaling pathways, and this can dramatically alter the actions of these compounds on specific brain circuits important for learning and memory and psychosis.