FIGURE 1.

Diagram of the experimental design for experiments 1 and 2. In experiment 1, the 10-s extension of an illuminated lever (CS) predicted the delivery of 0.2 mL ethanol (15% vol/vol; US) into a receptacle. There were 12 CS–US trials, and each trial was separated by an intertrial interval (ITI) of either 120, 240, or 360 s. Rats received an injection of either nicotine (0.4 mL/kg s.c.) or saline 15 min prior to each session. In experiment 2, the 8-s extension of an illuminated lever (CS) predicted the receipt of a single banana-flavored food pellet (US) into a receptacle. There were 25 CS–US trials, and each trial was separated by an ITI on a 90-s (60–150 s) variable time schedule. As in experiment 1, rats in experiment 2 also received an injection of either nicotine (0.4 mL/kg s.c.) or saline 15 min prior to each session.