Figure 1.

(A) Timeline. Incubation of drug craving procedure: rats are trained to self-administer a reward (up to 5 weeks) and then relapse is tested in early and late phases of abstinence, between tests rats undergo a forced-abstinence period (up to 25 weeks). During the relapse tests rats are re-exposed to the self-administration chambers and lever presses lead to contingent presentations of a discrete cue previously paired with reward delivery. (B) Incubation of drug craving in rats. Relapse tests: data are Mean±SEM number of non-reinforced lever presses during relapse tests at different days of abstinence from cocaine (Grimm et al., 2001), nicotine (Abdolahi et al., 2010), oxycodone (Fredriksson et al., 2020), heroin (Shalev et al., 2001), methamphetamine (Shepard et al., 2004), alcohol (Shepard et al., 2004) and fentanyl (Gyawali et al., 2021). (C) Incubation of non-drug rewards in rats. Relapse tests: data are Mean±SEM number of non-reinforced lever presses during relapse tests at different days of abstinence from sucrose (Harkness et al., 2010), saccharin (Aoyama et al., 2014), high-fat diet (Darling et al., 2016), and water (Grimm et al., 2012). *Different from abstinence day 1, p < 0.05. Data were redrawn, with permission, from the above cited references.