Figure 2.

Dose-dependent yawning elicited by (a) the D₃ agonist quinpirole (0.03–1.0 mg/kg, intravenously (i.v.)) and (b) the D₃ receptor-selective compound PG 619 (N-(3-hydroxy-4-(4-(2-methoxyphenyl)piperazin-1-yl)butyl)-4-(pyridin-2-yl)benzamide HCl) (0.03–1.0 mg/kg, i.v.) in cocaine-history (n=3, open bars) and cocaine-naïve monkeys (n=4, closed bars). Data are represented as mean±SEM number of yawns observed over a 30-min period. Asterisks (^*p<0.05; ^***p<0.001) indicate statistical differences between groups.