Intermittent presentations of ethanol sipper tube induce ethanol drinking in rats.

AIMS Intermittent presentations of the ethanol sipper have been reported to induce more ethanol drinking in rats than when the ethanol sipper was continuously available during the session. This intermittent sipper effect was observed in a social drinking situation, in which subjects experienced intermittent opportunities to interact briefly with a conspecific rat. The objective of this study was to evaluate the effects of the intermittent sipper procedure in situations providing for intermittent presentations of food, and, in addition, in situations that do not provide for intermittent presentations of another rewarding event. METHODS Four groups of male Long-Evans hooded rats, arranged in a 2 x 2 factorial design with two levels of Sipper Procedure (Intermittent vs Continuous) and two levels of Food procedure (Food vs No Food), were trained in drinking chambers. During each daily session, Intermittent Sipper groups received access to the ethanol sipper during each of 25 trials of 10 s each, while Continuous Sipper groups had access to the ethanol sipper during the entire session (approximately 30 min). During each session, Food groups received 25 presentations of food pellets while No Food groups received no food pellets. Ethanol concentrations in the sipper [3, 4, 6, 8, and 10% (vol./vol.)] increased across sessions. RESULTS More rapid escalation of ethanol intake was observed in the Intermittent Sipper groups than in the Continuous Sipper groups, and this effect was observed in both the Food and No Food conditions (P's < 0.05), which did not differ from one another. CONCLUSIONS Intermittent Sipper procedures provide less access to the ethanol sipper, yet induced more ethanol drinking than Continuous Sipper procedures. The intermittent sipper effect is not dependent on presentations of food. Implications for schedule-induced polydipsia and Pavlovian autoshaping are discussed.