Figure 1.

Schematic of the discrimination acquisition and testing procedures. Pretreatment on acquisition sessions was on a double alternation schedule (A,A,W,W) in which only 1 treatment was given per day. Acquisition sessions consisted of a 10 minute pre-treatment time where the chamber was inactive, followed by a 15 minute session in which the stimulus light activated randomly 10 times during the session (15 seconds each). On alcohol sessions, light offset was immediately followed by 4-second access to 0.1ml sucrose. On water sessions, light offset had no outcome. Cumulative test sessions consisted of 4 discrete tests. Each test was preceded by a 10 minute pretreatment off-period, followed by a 2 minute test in which a single, random light activation (15 sec.) occurred that was followed by sucrose access. Rats were then injected with the next dose and placed back in the chamber for the next session.