circulating orexigenic stomach-derived hormone that regulates energy homeostatsis mainly via hypothalamic growth hormone secretagogue receptor (Cheung & Mao, 2012; Horvath, Diano, Sotonyi, Heiman, & Tschöp, 2001; Kojima et al., 1999; Kojima & Kangawa, 2005; Tschöp, Smiley, & Heiman, 2000). There is some preliminary evidence that single nucleotide polymorphisms located in the pre-proghrelin gene (GHRL) and the gene responsible for the production of the ghrelin receptor (GHSR-1a) are associated with increased alcohol use and smoking in candidate gene association studies (Landgren et al., 2010; Suchankova et al., 2015). In prior rodent models, ghrelin increases alcohol consumption (Gregory et al., 2012; Jerlhag et al., 2009; Kaur & Ryabinin, 2010), enhances cocaine-induced locomotor stimulation and conditions place preference for cocaine (Davis, Wellman, & Clifford, 2007; Tessari et al., 2007; Wellman, Davis, & Nation, 2005).
