Figure 1.

Effects of intra-NAc shell LY379268 injections on context-induced reinstatement of heroin seeking. (a) Training: mean ± SEM infusions, and active and inactive lever responses during the 12 days of heroin self-administration training. Rats were trained on an FR-1 schedule with a 2.3 s timeout period; active lever responses reflect infusion + timeout responses. The unit dose of heroin was 0.1 mg/kg for the first six sessions and 0.05 mg/kg for the last six sessions (n = 25, three groups). (b) Extinction: mean responses on the previously active lever and on the inactive lever during extinction sessions conducted in the absence of heroin and in a context different from the training context (n = 25). (c) Test for reinstatement: active lever: mean responses on the active lever after bilateral intra-NAc shell injections of vehicle, 0.3 or 1.0 μg of LY379268 in the training or the extinction context. *Different from the vehicle condition, p 0.05 (n = 8-9/group). (d) Test for reinstatement: inactive lever: mean responses on the inactive lever after intra-NAc shell injections of vehicle or LY379268. (e) A representative picture of NAc shell injector tip and the approximate placements of the injectors' tip of the rats (Paxinos and Watson, 2005).