During 30 minute sessions that occurred 5 days per week, animals were trained to self-administer (according to a continuous schedule of reinforcement) a 10% ethanol (w/v) solution (0.1 ml) in standard operant chambers (Med Associates, St. Albans, VT) with custom drinking wells (Behavioral Pharma, La Jolla, CA) using a sweetener-fade procedure (Samson, 1986) that has been described in detail elsewhere (Walker et al., 2007). Acquisition of the operant response occurred using a sweetened fluid (0.125% saccharin and 3% glucose) that is preferred to other sweeteners such as sucrose (Valenstein, Cox, & Kakolewski, 1967) without necessitating water or food deprivation. Next, 10% ethanol (w/v) was added to the solution and then over three weeks, the sweetener was removed from the solution with 10% ethanol as the final solution. Once responding stabilized (defined as three sessions with < 10% deviation), animals were assigned to one of the three different treatment conditions (example of dependence-induced escalation, chronic FN-439 treatment or acute FN-439 treatment) that were matched based on ethanol self-administration.
