INTERLEUKIN-1 INHIBITS SEXUAL-BEHAVIOR IN FEMALE BUT NOT IN MALE-RATS

The cytokine interleukin-1 (IL-1) is released by a variety of cells in response to infection or injury. IL-1 produces several neuroendocrine and behavioral effects, including a suppression of reproductive funct ions and goal-directed behaviors. The present study examined the effec t of IL-1 on sexual behavior in male and female rats. The following be havioral tests were employed: preference for a sexually appropriate pa rtner, preceptive (soliciting) behavior, the lordosis quotient (sexual receptivity), and mating performance. peripheral (ip) IL-1 beta, 2 or 10 mu g/kg, injected 2 h before testing, significantly suppressed pre ceptive behavior and sexual receptivity in intact, normally cycling fe males. In ovariectomized rats treated with ovarian hormones, IL-1 beta (2 or 10 mu g/kg) significantly decreased the preference for a sexual ly active male partner and suppressed preceptive behavior and sexual r eceptivity. These effects were evident 2, but not 4 or 6, h after IL-1 beta administration. Intracerebroventricular administration of IL-1 b eta (10 ng/rat) also suppressed the preference for a male partner and preceptive behavior in normally cycling females. Similar doses of IL-1 beta had no suppressive effect on any aspect of male sexual behavior, and the highest dose even increased the preference for a receptive fe male partner. In contrast to the gender-specific effects on sexual beh avior, the suppressive effects of IL-1 beta on activity in the open-fi eld test were comparable in male and female rats. The inhibition of fe male sexual behavior by IL-1 may be adaptive, in that it prevents conc eption while the animal is sick, thus reducing the risk of spontaneous abortion or abnormal development. (C) 1995 Academic Press, Inc.