Acute and repeated low dose lipopolysaccharide differentially influences opposite-sex odour preference in male and female mice

Infection threat affects social preferences and mate choice across species. Female mice have been shown to avoid the odours of sick males acutely treated with relatively high doses of lipopolysaccharide (LPS), the cell wall of Gram-negative bacteria. However, less is known about the responses of both sexes to more naturalistic low level infection threat. Here we considered the responses of both male and female mice to the odours of opposite sex individuals acutely and repeatedly treated with very low and low doses of LPS (1.0 and 25 μg/kg, respectively). There was minimal avoidance of the odours of individuals acutely treated with 1.0 μg/kg LPS, whereas repeated treatment (days 1, 4 and 7), which elicited sensitization (priming), resulted in significant Day 7 avoidance. Conversely, the odours of individuals acutely treated with 25 μg/kg of LPS elicited significant avoidance, whereas repeated treatment, which lead to the development of tolerance, attenuated avoidance. In all cases females displayed a greater avoidance than males of opposite sex odours. Our results show that both male and female mice are sensitive to the nature of the infection status and threat conveyed by the olfactory cues associated with low levels of infection.