Foster DJ, Wilson JM, Remke DH, Mahmood MS, Uddin MJ, Wess J, Patel S, Marnett LJ, Niswender CM, Jones CK, Xiang Z, Lindsley CW, Rook JM, Conn PJ. Antipsychotic-like Effects of M4 Positive Allosteric Modulators Are Mediated by CB2 Receptor-Dependent Inhibition of Dopamine Release. Neuron. 2016 Sep 21;91(91). 1244-52. PMID: 27618677 [PubMed] PMCID: PMC5033724 NIHMSID: NIHMS815091.
Muscarinic receptors represent a promising therapeutic target for schizophrenia, but the mechanisms underlying the antipsychotic efficacy of muscarinic modulators are not well understood. Here, we report that activation of M4 receptors on striatal spiny projection neurons results in a novel form of dopaminergic regulation resulting in a sustained depression of striatal dopamine release that is observed more than 30 min after removal of the muscarinic receptor agonist. Furthermore, both the M4-mediated sustained inhibition of dopamine release and the antipsychotic-like efficacy of M4 activators were found to require intact signaling through CB2 cannabinoid receptors. These findings highlight a novel mechanism by which striatal cholinergic and cannabinoid signaling leads to sustained reductions in dopaminergic transmission and concurrent behavioral effects predictive of antipsychotic efficacy.