A dopamine (DA) D1 receptor agonist elevates GluA1 phosphorylation in the striatum.
DA D2 receptors augment efficacy of the D1 receptor agonist.
A positive modulator of muscarinic M4 receptors (M4R) inhibits D1/D2 synergy.
D1/D2 synergy determines the number of GluA1 and PKA at extrasynaptic sites.