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 in these two studies is more difficult to reconcile because of methodological differences. In Hansson et al (2007), URB597 was microinjected into the PFC where Cippitelli et al (2008) delivered the drug systemically altering AEA concentrations throughout the organism. These widespread changes in AEA levels could produce effects that mute those elicited by localized injection into the PFC. As a result, the sum of available data support the hypothesis that brain AEA concentrations are enhanced following ethanol consumption, and the increased AEA levels contribute to the reinforcing and motivational actions of the drug.
