Fig. 2.

The experimental groups did not differ in their acquisition of instrumental responding for cocaine, heroin or food. All rats acquired cocaine (a) or heroin (b) self-administration within ten daily sessions. Similarly, rats trained to lever press for food (c) reached their maximal level of reinforcers earned by the second day of training. Moreover, prior to treatment, rats assigned to the masitinib group did not differ from those assigned to the control group in their intake of cocaine (a), heroin (b) or food (c)