Baseline and cocaine-induced motor activity were assessed in wild-type and Girk−/− mice (4-10 wk) using automated open field environments, as described (Pravetoni and Wickman 2008). Baseline activity data were obtained during 60-min daily sessions over a consecutive 3-d period. On day 3, subjects were given injections of saline (i.p.) and placed in the open field for 60-min. Subsequently, subjects were randomly assigned to groups that received saline or one of four cocaine doses (3, 15, 30, or 60 mg/kg, i.p.). Total distance traveled after the injection was monitored for 60 min.
