High level of circulating testosterone abolishes decline in scent attractiveness in antigen-treated male mice

We hypothesized that a decrease in the attractiveness of odours from infected male mice, Mus musculus could be caused by either parasite-induced changes in host metabolism (parasite-dependent pathway) or activation of the immune defence system (immune-dependent pathway). Activation of the immune defence system by nonreplicated antigens (sheep red blood cells, SRBC) is sufficient for a decrease in both scent attractiveness and the concentration of plasma testosterone in male mice. Since the scent attractiveness of male mice depends on androgen levels, we studied the olfactory effect of SRBC in sham-operated, gonadectomized and testosterone-treated male mice of the outbred strain ICR. SRBC administration resulted in a decline in both sexual odour attractiveness and concentration of urinary proteins in sham-operated control males. The effect of SRBC on concentration of urinary proteins was abolished by stabilizing the testosterone level in gonadectomized and androgen-treated males. At the same time, only the high dose of testosterone was sufficient to maintain the scent attractiveness in SRBC-treated males at the pretreatment level.