Reliable self-administration of ethanol in dependent animals using ethanol vapor exposure has been extensively characterized in rats, in which animals obtain blood alcohol levels in the 100–150 mg% range (Roberts et al. 1999, 2000). Similarly, rats with a history of alcohol dependence show increased self-administration of ethanol, even weeks after acute withdrawal (Roberts et al. 2000). In a variant of alcohol vapor exposure with more face validity, intermittent exposure to chronic ethanol using alcohol vapor chambers (14 h on/10 h off) produces more rapid escalation to increased ethanol intake and higher amounts of intake (O’Dell et al. 2004; Rimondini et al. 2002), and blood alcohol levels are reliably above 140 mg% after a 30 min session of self-administration in dependent animals (Richardson et al. 2008). In both the liquid diet and ethanol vapor procedures, alcohol intake is directly related to the blood alcohol range and the pattern of intermittent high-dose alcohol exposure (Gilpin et al. 2009). Although the alcohol vapor model may have limited face validity, considering that alcohol is passively administered to animals, numerous studies demonstrated that it also has robust predictive validity for alcohol addiction (Heilig and Koob 2007; Koob et al. 2009).
