The effects of methamphetamine (MA), which are predominantly mediated by dopaminergic and serotonergic systems, may also involve the endogenous opioid systems. Indeed, work in animals has shown that naloxone administration can block behavioral sensitization to repeated MA exposure (Chiu et al., 2005). However, the few studies investigating the effect of the A118G SNP in MA dependence failed to find an association (Ide et al., 2004; Ide et al., 2006) (Table 1).
