Repeated restraint stress impacts feeding under novelty differently in males and females

Eating behavior changes under chronic stress and in response to novelty, yet their interaction has not been examined. The current study examined how repeated restraint stress impacts the approach and consumption of a novel food in a novel feeding environment in adult male and female rats. Rats in the stress condition received 7 sessions of motor restraint stress over 9 days. Rats in the control condition experienced the same handling and transport but instead of restraint remained in their home cages. The stress experience impacted the body weight of males but not females. Males in the stress condition weighed less than controls at the end of the restraint stress protocol and maintained lower body weight throughout the rest of the experiment. Following restraint stress, all rats were presented with a novel, palatable (high sucrose) food in a novel context for four habituation sessions. All subjects increased feeding across the four sessions, indicating that they habituated to novel stimuli. During the first exposure to novelty, females who experienced repeated restraint stress consumed more of the palatable, novel food in the novel environment, while males who experienced restraint stress consumed less. This interaction effect diminished with further sessions, indicating that these stress-induced behavioral changes were temporally sensitive and selective to eating under novelty. Latency to approach and latency to start eating the novel food decreased across sessions. During the second exposure to novelty, females in the stress condition approached the novel food faster than any other group and started eating faster than males in the stress condition. These results demonstrate that repeated restraint stress alters food consumption under novelty divergently in males and females. The behavior in females suggests that repeated restraint stress increases risk-taking behavior towards a palatable but unproven food reward in an uncertain environment.