Hunger alters approach-avoidance behaviours differently in male and female mice
BackgroundThe decision about whether to approach or avoid a reward while under threat requires balancing competing demands. Sex-specific prioritisations (e.g. mating, maternal care), or generalised prioritisations (e.g. feeding, drinking, sleeping) may differently influence approach-avoidance behaviours based on the level of "risk" and homeostatic need state of the organism. However, given known sex differences in key aspects that may influence this behaviour, direct comparison of how male and female mice make decisions to approach or avoid a dangerous area while in a fasted state have yet to be conducted. MethodsWe conducted several approach-avoidance tasks with varied levels of risk and reward in male and female mice that were either fasted or sated (fed). Mice underwent a light-dark box, elevated plus maze, baited large open field and runway task to assess their approach and avoidance behaviour. ResultIn the light-dark box and elevated plus maze, when no reward was available, fasted female mice showed greater approach behaviours than male counterparts. In the baited large open field, when reward was available, both sexes showed increased approach behaviours when fasted. However, when sated, male mice conversely showed greater approach behaviours compared to sated female mice. In the runway task, while sated mice failed to learn, fasted male mice inhibited their reward consumption in response to increased shock intensity; however, fasted female mice were resistant to increased shock intensity. ConclusionsOur study identifies sex differences in decision making behaviour in mice based on satiety state across a number of approach-avoidance tasks. We highlight several nuances of these differences based on reward availability and punishment intensity. These results shine a lens on fundamental differences between the sexes in innate, survival driven behaviours that should be taken into account for future studies. Plain English summaryEveryday decision making is often accompanied by conflict - whether we make the most appropriate decision or not can be influenced by both internal and external factors. Environmental threats and physiological pressures, such as hunger, can influence decision-making processes skewing the risk/reward ratio, yet how this may differ between the sexes has not been explored in detail. Here we used several tasks that assess decision-making in mice while manipulating the levels of risk or reward. Our findings show fasted female mice are more willing to engage in "risky" behaviour compared to fed female mice when risk levels were low, and no food reward was available. However, when a food reward was available, but risk levels were low, both male and female fasted mice were more likely to engage in risky behaviour compared to fed mice. Finally, when risk levels were high and food reward was available, fasted female mice continued to engage in risky behaviour, while male fasted mice were not. Together our study identifies nuanced sex differences in how male and female mice make decisions influenced by both physiological (hunger) and environmental threats and highlight the importance of understanding fundamental differences between the sexes in behaviour. Highlights- Fasted female mice showed greater approach behaviours compared to fasted male counterparts in tasks without reward availability. - Fasted mice of both sexes displayed greater approach behaviours when a reward was available, compared to sated controls. - Fasted male mice inhibited reward consumption under increased shock intensity, whereas fasted female mice were resistant to mild foot shock.