Extended Pavlovian conditioned approach training and devaluation in Long-Evans rats using time-restricted feeding
Pavlovian conditioned approach (PCA) is a useful tool in studying compulsive- and addictive-like behaviors. PCA pairs a cue with reward delivery and rats typically differentiate into three phenotypes (sign-trackers, goal-trackers, and intermediates) based on behavior during the reward-paired cue presentation. Sign-trackers, who preferentially interact with the cue, are more likely to engage in compulsive behaviors and have decreased behavioral flexibility compared to goal-trackers, who preferentially interact with the food cup. However, one limitation to PCA is the use of food deprivation conditions that maintain rats at 80-90% of ad libitum weight, likely increasing stress which may bias animals towards sign-tracking behavior. Furthermore, most behavioral analysis only examines lever pressing and food cup entry, overlooking other behaviors that may better define phenotypes. In the current study male and female Long-Evans rats underwent an extended PCA training paradigm followed by satiety-induced reward devaluation under time-restricted feeding (TRF) conditions. Under TRF, rats continued to gain weight across PCA training and maintained caloric intake relative to ad libitum intake. Expanding the scope of behavioral analysis increased the proportion of ST rats in both early and late PCA training. Rats also increased the time spent interacting with the food cup during the inter-trial interval across extended PCA training. All rats were sensitive to satiety-induced reward devaluation, regardless of sex or devaluation condition. This study helps establish a PCA method optimized for Long-Evans rats with relevance for identifying PCA phenotypes contribution to dysregulated behavior in the context of chronic stress and obesity.