receptor subtypes (Helms et al. 2008). In contrast, Platt and collaborators (Platt et al. 2005) reported a prominent role for the α5- but not the α1-GABAA receptors in the discriminative stimulus effects of ethanol and the ethanol-like effects of benzodiazepines in squirrel monkeys. However, the ethanol-like discriminative stimulus effects are complex. For instance, the discriminative stimulus effects of low doses of ethanol (1.0 g/kg) are predominantly mediated by GABAA receptor positive modulation, while higher doses (2.0 g/kg) require other systems such as N-methyl-D-aspartate (NMDA) receptors (Grant 1999). Indeed, ethanol’s discriminative stimulus effects are mediated by interactions of GABAA, NMDA, and metabotropic glutamate receptor subtype 5 (mGluR5), located in specific limbic brain regions such as nucleus accumbens core and amygdala (Besheer et al. 2003; Besheer and Hodge 2005; Hodge and Cox 1998).
