Genetic selection studies have resulted in a number of high drinking lines of mice and rats (see Bell et al., 2006; Green and Grahame, 2008). The alcohol-preferring (P) and -nonpreferring (NP) rat lines are one of the most extensively examined animal models of alcoholism (Li et al., 1993). These rats were developed for differences in home cage ethanol consumption in order to study ethanol drinking behaviors and their consequences (Bell et al., 2006; Lumeng et al., 1977). Selectively bred P rats have been shown to voluntarily consume levels of 10% ethanol of >5 g/kg/day, with an ethanol preference ratio (vs. water) of greater than 2:1. The NP rats generally consume levels of 10% ethanol of <1.5 g/kg/day, with an ethanol preference ration of less than 0.2:1. These lines have been the focus of intensive study of the behavioral, neurobiological, and neurophysiological factors that contribute to ethanol consumption (for reviews, see Bell et al., 2006; Li et al., 1993; McBride and Li, 1998).
