Based on accumulating evidence, the Src kinase Fyn plays a key role in drug addiction, and long-lasting activation of Fyn has been previously illustrated in alcohol addiction (Wang et al., 2007; Wang et al., 2010; Darcq et al., 2014) and cocaine or heroin addiction (Schumann et al., 2009; Egervari et al., 2020). This evidence concerns the gene FYN and heroin dependence.