– Dopamine D3 receptor agonist 13a selectively targets the dopamine D3 receptor over dopamine D1, D2, and D4 receptors, with affinities (Ki values) of 0.14, 4,600, 2.85, and 756 nM, respectively. It also interacts with serotonin (5-HT) receptor subtypes 5-HT1A, 5-HT2A, 5-HT2B, and 5-HT2C, with Ki values of 6, 54, 1.47, and 252 nM, respectively. While acting as a partial agonist at dopamine D2 receptors (EC50 = 2.26 nM in a G protein recruitment assay), it serves as an antagonist at dopamine D3 receptors (IC50 = 4.62 nM). Additionally, Dopamine D3 receptor agonist 13a, at a dose of 3 mg/kg, has been shown to reduce cocaine self-administration in rats.