Sex differences in fear-induced feeding cessation: prolonged effect in female rats

Fear inhibits food intake. Cessation of eating in anticipation of danger is an adaptive response that prepares an organism for an imminent threat, but it could become maladaptive when persistent. To begin to examine the underlying mechanisms, we developed an animal model for fear-cue induced inhibition of feeding. In that preparation, food-deprived rats stop eating when presented with a tone that signals a foot-shock based on prior associations. Here, we examined whether there are sex differences in adult male and female rats. We found that female rats showed sustained fear-cue induced feeding inhibition compared to males during the extinction. During the first of four extinction tests with tone presentations, both male and female rats showed similar, robust cessation of eating. Rats of both sexes that previously received tone-shock pairings ate significantly less than the control rats that received tones without shocks during training. Male rats extinguished this behavior during the second test, while females continued to show the effect during the second and third tests, and extinguished during the fourth test. The findings provide a novel framework for investigation of sex differences in the control of feeding and the underlying brain substrates. The animal model may also be informative for understanding human eating and associated disorders. In particular, the potential contribution of fear in the maintenance of low food intake in anorexia nervosa is hypothesized.