Impact of satiety on palatable food associative learning and consumption in male and female adult rats

Abstract

Hedonic and memory mechanisms can stimulate food cravings and consumption in sated individuals, promoting binge eating and obesity. Despite that, how satiety impacts learning and memory about cues for palatable food in males and females remains unclear. This is the first study to directly compare food associative learning, extinction, and memory renewal between hungry and sated subjects of both sexes. Food-restricted and sated male and female adult Sprague Dawley rats were trained in Pavlovian cue-food conditioning sessions, followed by cue-only presentations during extinction in a different context. They were then tested for renewal of conditioned responding to the food cue by return to the conditioning context. Conditioned responding was assessed through foodcup approach behavior. These rats were also tested for consumption of palatable food and chow before and after the learning and memory protocol. Sated rats demonstrated learning, extinction, and renewal of conditioned responding, indicating that physiological hunger is not required for learning and memory of palatable food cues. There were differences during cue-food acquisition, food-deprived rats learned faster and reached a plateau in conditioned responding sooner than sated rats. However, there were no differences after the fourth session, when sated rats reached the same level of responding as the food-deprived rats. There were sex differences during early acquisition under sated but not hungry states. Sated females had higher conditioned responding than sated males, while food-deprived rats of both sexes responded similarly. Extinction and renewal tests showed that both hungry and sated rats successfully decreased and subsequently renewed their conditioned responses. These results demonstrate the durability of learning and persistence of food-cue memory regardless of hunger state. Consumption tests found that all rats prefer palatable food compared to chow. Females, particularly when sated, consumed more palatable food compared to males. Higher palatable food consumption and learning in females suggest an enhanced sensitivity to palatable rewards. Correlation analyses found a positive relation between the amounts of food rats consumed and their conditioned responding in both sexes. These results demonstrate robust associative learning and memory under satiety and add evidence of sex differences in hedonic food motivation.