“…More recently, studies in animals with a history of dependence (chronic but ‘forced’ ethanol exposure and withdrawal) have demonstrated that ethanol can serve as a potent negative reinforcer as well. For example, increased ethanol self-administration was shown in studies where dependence was induced by chronic administration of ethanol in a nutritionally fortified liquid diet (that served as the animals’ sole source of calories and fluid) (Brown, Jackson, & Stephens, 1998; Chu, Koob, Cole, Zorilla, & Roberts, 2007; Gilpin et al, 2009; Schulteis, Hyytiä, Heinrichs, & Koob, 1996), via intragastric infusions (Cunningham, Fidler, Murphy, Mulgrew, & Smitasin, 2013; Fidler et al, 2011; Fidler et al, 2012), and via inhalation of alcohol vapors (e.g., Becker & Lopez, 2004; Rimondini, Arlinde, Sommer, & Heilig, 2002; Roberts, Heyser, Cole, Griffin, & Koob, 2000). In such studies, the altered physiological state associated with dependence along with the capacity for ethanol to alleviate withdrawal symptoms is posited to not only sustain ethanol self-administration, but also promote escalation of intake (Becker, 2008; Becker, 2013; Heilig, Egli, Crabbe, & Becker, 2010).…”