Figure 3.

SB334867 reduces the effort, but not cue-learning for palatable reinforcers. In the effort based task, rats had free access to one arm on the T-maze baited with 3–45 mg of pellets of regular food or could climb a barrier to obtain equal pellets of high fat chocolate food. A, Timeline depicting the habituation, training and testing procedures used. B, C, Rats must climb (B) a 15 cm barrier (n = 8 rats) or (C) a 30 cm barrier (n = 9 rats) to obtain high fat food. Bars represent mean and SEM of the ratio of high fat chocolate food arm entries on the last day of untreated training (shaded bars), 15 min after a vehicle injection (open bars), or SB334867 (filled bars). Treatment of SB334867 significantly reduces the preference for the high fat chocolate food arm (*p < 0.05, **p < 0.001, repeated measures ANOVA). D, Schematic of the cue-conditioning paradigm. Delivery of a sucrose pellet was contingent on a tone/light conditioned stimulus (CS+) during a daily 30 min session. E, Conditioned-approach behavior, measured as the ratio of nosepokes during the CS+ to the nosepokes 30 s following CS+ presentation, was not different between rats having daily injections of vehicle (i.p., n = 11) or SB334867 (15 mg/kg, i.p., n = 11, p > 0.05).