DIFFERENT RECEPTOR MECHANISMS MEDIATE THE EFFECTS OF ENDOTOXIN AND INTERLEUKIN-1 ON FEMALE SEXUAL-BEHAVIOR

Activation of the immune system by Lipopolysaccharide (LPS) produces p hysiological, neuroendocrine and behavioral effects, some of which are mediated by cytokine production. We have previously shown that the cy tokine interleukin-1 (IL-1) inhibits sexual behavior in female, but no t male rats, while producing a comparable suppression of locomotion in both sexes. The present study examined the effects of LPS on sexual b ehavior and locomotion of male and female rats, and the involvement of IL-1 receptors in mediating the effects of IL-1 and LPS on females' b ehavior. Peripheral (i.p.) administration of LPS (50 or 250 mu g/kg) s ignificantly decreased sexual behavior in females, up to 6 h after adm inistration, while it had no effect on male sexual behavior. However, locomotor activity, measured in the open-field test, was similarly red uced by LPS in both males and females. Pretreatment with the IL-1 rece ptor antagonist(IL-1ra) either i.p. (10 mg/kg) or intracerebroventricu larly (i.c.v.) (50 mu g/rat) did not prevent the inhibition of female sexual behavior and locomotion induced by either i.p. (50 mu g/kg) or i.c.v. (200 or 400 ng/rat) administration of LPS, respectively. Howeve r, identical doses of IL-1ra significantly reversed the effects of IL- 1 beta, administered either i.p. (5 mu g/kg) or i.c.v. (50 ng/rat), re spectively. These results demonstrate that both LPS and IL-1 beta prod uce marked inhibition of sexual behavior in female, but not in male ra ts. However, IL-1 receptors are not required for the effects of LPS on sexual behavior in female rats. (C) 1997 Elsevier Science B.V.