However, several studies dispute the role of increased levels of AEA in ethanol consumption. The earliest study to suggest that enhanced AEA levels are not associated with increased ethanol intake utilized the putative EMT inhibitor, AM404. Treatment with AM404 reduced the number of active lever responses in rats trained to self-administer ethanol (Cippitelli et al., 2007). However, this effect was not blocked by CB1, CB2, or TRPV1 antagonists raising the possibility that AM404 produced these effects via a mechanism independent of AEA inactivation. In marked contrast to the study by Hannson et al (2007), systemic administration of URB597 failed to enhance ethanol self-administration or the reinforcing properties of ethanol in Wistar rats, and treatment with URB597 did not affect ethanol consumption in Marchigian Sardinian alcohol preferring rats (msP rats; Cippitelli et al., 2008). It is possible that the lack of effect of URB597 on ethanol drinking in msP rats was due to a ceiling effect where these rats consumed enough ethanol at baseline that further enhancement by FAAH inhibition was not possible. However, the discrepancy between the ethanol self-administration data
