The immunobiology of sexual behavior: Gender differences in the suppression of sexual activity during illness

Following infection or injury, sick individuals experience profound psychol ogical and behavioral changes, such as anorexia, depressed activity, and re duced self-care behavior. In the present review, we present evidence for a gender-difference in the behavioral response to sickness. Specifically, fol lowing immune activation, sexual activity is suppressed in female, but not in male rats. This gender difference is specific to sexually related respon ses, because other behaviors, such as locomotion, are equally affected by i mmune challenges in males and estrous females. The suppression of female se xual behavior, induced by either endotoxin (lipopolysaccharide), or the cyt okine interleukin-1 (IL-1), are mediated by central mechanisms that are ind ependent of alterations in ovarian hormone secretion. Furthermore, synergis tic effects of the cytokines IL-1 and tumor necrosis factor alpha (TNF alph a) are involved in modulating sexual behavior in sick females, and prostagl andins synthesis is required for the effects of IL-1 on female sexual behav ior. The gender difference in the behavioral response to immune activation may be related to the findings that at the same doses and timing in which I L-1 suppressed sexual activity in female but not in male rats, females prod uced more prostaglandin E-2 (PGE(2)) in the brain, and less corticosterone than males. Finally, we are suggesting that the suppressive effect of cytok ines on female reproductive behavior may serve as a mechanism to reduce con ception during infection, which exposes the mother and the fetus to dangers such as spontaneous abortions, preterm labor and maternal mortality. (C) 1 999 Elsevier Science Inc.