EFFECTS OF INTERLEUKIN-1 ON SEXUAL ATTRACTIVITY IN A MODEL OF SICKNESS BEHAVIOR

Interleukin-1 (IL-1), a cytokine secreted by activated macrophages, in hibits sexual behavior in female but not male rats. The present study examined the effects of IL-1 on sexual attractiveness of the injected animal and on the sexual responses exhibited by its mating partner. In Experiment I, a male rat was placed with an estrous female, injected with either IL-1 beta (2 or 10 mu g/kg) or saline. Males exhibited mor e mounts and intromissions per ejaculation and longer ejaculation late ncies with IL-1-than with saline-injected females. In a second experim ent, a male was placed with two estrous females, one injected with IL- 1 beta (5 mu g/kg) and the other with saline. Males performed less sex ual behavior and spent less time with the IL-1-injected female. In a t hird experiment, an estrous female was placed with two males, one inje cted with IL-1 beta (5 or 20 mu g/kg) and the other with saline. IL-1 had no effect on the time spent by the female with each male, and only the high dose reduced preceptive (courtship) behavior. In conclusion, IL-1 administration to females reduces the quality of the sexual act, thus reducing the chances for conception during infection, which is a ssociated with spontaneous abortion and abnormal development of the fe tus. In males, the chances for reproduction are less affected by IL-1, possibly because reproduction during infection is not as risky in mal es as in females. (C) 1998 Elsevier Science Inc.