Effects of rolipram or saline on cocaine-related behaviors (a, b) Rolipram (0.1 mg/kg, i.p.) or saline was administered 20 min before cocaine (10 mg/kg) injections. (a) Repeated cocaine produced a significantly greater sensitization of locomotor activity in GXE mice than CTL, E, and G mice (Saline). Co-administration of rolipram blocked the augmentation of cocaine-induced locomotor sensitization in GXE mice (Rolipram). ** p < 0.01. n = 7 each. (b) In a CPP test, preference for the cocaine-paired side was significantly elevated in GXE mice when compared with CTL, E, and G mice (Saline). Co-administration of rolipram completely blocked cocaine-induced conditioned place preference in GXE, but not CTL, E, or G mice (Rolipram). * p < 0.05, ** p < 0.01. n = 5 each.