Discriminative control by deprivation states and external cues in male and female rats

Previous research indicates that decisions about when to eat in response to food cues in the environment are based on interoceptive energy states (i.e., hunger and fullness) and learning about and remembering prior eating experiences. However, this animal model has exclusively been tested on male rodents. Despite evidence that women are more susceptible to obesity and cognitive disorders associated with excess weight (e.g., Alzheimer's disease) than men, the generality of these findings with males to females remains unknown. To address this gap, the current research investigated associative learning mechanisms involved in food intake control in females by training both males and females in a Pavlovian deprivation discrimination in which varying levels of food deprivation are trained with competitive external cues to signal reward. In Experiment 1, male and female rats showed similar performance in discriminating between 0 and 24 h deprivation state/external cue compounds and in subsequent tests, confirming stimulus control by deprivation states. Experiment 2 assessed learning about more ecologically valid 0 and 4 h deprivation states in competition with external cues in both males and females. With the low-level deprivation state parameters, females outperformed males in discriminative control by deprivation states, particularly on the contingency rewarded under satiation and not deprivation. While females showed an enhanced degree of energy state processing under some deprivation conditions, overall, these findings suggest similar mechanisms of learned appetitive control in both sexes.