Measuring the appetitive strength of ethanol: use of an extinction trial procedure.

Assessing the motivational level related to gaining access to ethanol (appetitive strength) is critical in understanding the human behavioral processes described as "craving." Use of an animal model that separates the behavior required to obtain the opportunity to consume ethanol from the actual consumption allows for independent measures of appetitive strength that are not intermixed with the effects of the consumed ethanol. In this model, two different methods have been applied to determine the appetitive strength: an across-sessions breakpoint procedure and single-session extinction trials. Although both methods provide an estimate of appetitive strength, the current studies were performed to provide some comparison between them. From the results and comparison with findings from prior studies, it was determined that the breakpoint procedure gave the most stable and potentially least influenced measure of appetitive strength. On the other hand, extinction trials in general provided a stable measure, somewhat different from breakpoint, that could be influenced by behavioral effects other than those related to ethanol consumption. Ethanol intakes were in a pharmacologically relevant range, averaging approximately 1.0 g/kg during 20 min of access to the solutions. Both the breakpoint and extinction measures provide additional evidence of a separation between the behavioral processes of ethanol seeking and ethanol drinking, as there was no relation between lever-press responding and ethanol intake. Thus, when choosing a method, it is possible to assess the appetitive strength of ethanol. However, care should be exercised to avoid misinterpretation of results.