Autoshaping of ethanol drinking in rats: effects of ethanol concentration and trial spacing.

In two studies, we evaluated the effects of ethanol concentration and trial spacing on Pavlovian autoshaping of ethanol drinking in rats. In these studies, the brief insertion of an ethanol sipper conditioned stimulus (CS) was followed by the response-independent presentation of food unconditioned stimulus (US), inducing sipper CS-directed drinking conditioned responses (CRs) in all rats. In Experiment 1, the ethanol concentration in the sipper CS [0%-16% volume/volume (vol./vol.), in increments of 1%] was systematically increased within subjects across autoshaping sessions. Groups of rats received sipper CS-food US pairings (Paired/Ethanol), a CS-US random procedure (Random/Ethanol), or water sipper CS paired with food US (Paired/Water). In Experiment 2, saccharin-fading procedures were used to initiate, in the Ethanol group, drinking of 6% (vol./vol.) ethanol in 0.1% saccharin or, in the Water group, drinking of tap water in 0.1% saccharin. After elimination of saccharin, and across days, the duration of access to the sipper CS during each autoshaping trial was increased (5, 10, 12.5, 15, 17.5, and 20 s), and subsequently, across days, the duration of the mean intertrial interval (ITI) was increased (60, 90, 120, and 150 s). In Experiment 1, Paired/Ethanol and Random/Ethanol groups showed higher intake of ethanol, in terms of grams per kilogram of body weight, at higher ethanol concentrations, with more ethanol intake recorded in the Paired/Ethanol group. In Experiment 2, the Ethanol group drank more than was consumed by the Water group, and, for both groups, fluid intake increased with longer ITIs. Results support the suggestion that autoshaping contributes to sipper CS-directed ethanol drinking.