Evaluating Sex and Line Differences in Successive Negative Contrast and Ethanol Consumption Using Alcohol Preferring and High Alcohol Drinking Rats

Abstract

A loss of a job or relationship are a few examples of unexpected reward loss. Life events such as these can induce negative emotional reactions (e.g., anxiety and stress) which have been associated with increased drinking and in turn, an increased risk of developing an alcohol use disorder (AUD) (Keyes et al., 2011, Sinha, 2008). The present study used a consummatory successive negative contrast (SNC) procedure to demonstrate unexpected reward loss reactivity in two lines selectively bred to consume high amounts of ethanol, alcohol preferring (P) and high alcohol drinking (HAD) rats. Following this reward loss, animals were given free access to ethanol to determine if ethanol consumption would increase to negate any negative emotional reaction provoked by this loss. P rats demonstrated a longer contrast effect than HAD rats, indicated by a longer recovery time following the downshift in reward. Conversely, HAD males did not demonstrate a contrast effect following this downshift in reward. Surprisingly, P rats who experienced a loss of reward consumed significantly less ethanol than animals who did not. Lastly, an individual measure of contrast size, or shift ratio, was significantly associated with greater ethanol consumption in HAD males only, who did not display a contrast effect. These data indicate different reactivity to SNC between these two lines and sexes, suggesting different genetic and sex-related mechanisms underlying sensitivity to an unexpected loss of reward.