Enhancement of the hedonic value of an expected reinforcer following prior frustration: An animal model for studying binge-like episodes.

Abstract

INTRODUCTION: Reward delay-induced frustration leads to increased intake upon re-encounter and an enhanced motivational state for the omitted reinforcer. This phenomenon may be explained by changes in the palatability of the reinforcer (liking) or its expected value (wanting). OBJECTIVE: To evaluate whether increased intake following frustration events leads to alterations in liking. METHOD: Adult Sprague-Dawley rats were food-restricted to 83 % of their ad libitum weight. Dependent variables included sucrose solution intake (ml), burst duration, and number of bursts. In Experiment 1, rats were exposed to either a 4 % or 32 % sucrose solution over five 5-minute trials. Experiment 2 included three groups, all exposed to a 32 % sucrose solution over five 5-minute trials. On day six, the Non-Delay group received immediate access to the 32 % solution, whereas the Delay-2 and Delay-10 groups were required to wait 2 or 10 min, respectively. On day seven, all groups accessed the 32 % solution without delay. This cycle - one trial with delay followed by one without delay - was repeated five times. RESULTS: In Experiment 1, the 32 % condition showed higher intake and longer burst duration than the 4 % group. In Experiment 2, Delay-10 and Delay-2 animals exhibited higher intake and burst duration than Non-Delay animals. DISCUSSION: Increased intake following frustration events appears to involve an enhancement of the hedonic component, suggesting that elevated consumption may be driven by increased liking. Furthermore, this effect was more pronounced in animals exposed to higher levels of frustration (10-minute delay).