Modulation of exploratory behavior in female mice by protein-borne male urinary molecules

Male pheromones are believed to attract females and repel male mice in open field tests but, when tested in more complex environments, they can attract male mice in usually avoided areas. Females were tested in an apparatus with one dark and one light side, in the absence or presence of male urine or the major urinary proteins (MUPs) bearing the natural ligands. Diestrous females were slower in leaving from the dark area when male urine or MUPs were present in it. Estrogen-primed females showed the opposite behavior, with an increase in the same latency. The light-avoidance behavior of prepubertal females, or females reared without males was not influenced by the presence of male chemosignals. The results show that adult female mice can react to MUP-borne volatiles as to adult male urine and use them as cues of male mice, if they were previously exposed to male cues during infancy. MUP-borne molecules are, thus, the olfactory trace of males in the environment and modulate mice exploratory behavior.