DEFECT IN INTERLEUKIN-1-BETA SECRETION PREVENTS SICKNESS BEHAVIOR IN C3H HEJ MICE/

To examine the role of interleukin-1 beta (IL-1 beta) in mediating sic kness, we studied the effects of lipopolysaccharide (LPS) and IL-1 bet a on social behavior in endotoxin-responsive C3H/HeOuJ (OuJ) mice and endotoxin-resistant C3H/HeJ (HeJ) mice. Whereas LPS (1, 10 and 100 mu g) depressed social behavior and body weight compared to saline in OuJ mice, in HeJ mice it did not. To determine if the refractoriness of H eJ mice to the behavioral effects of LPS was related to secretion of I L-1 beta, in a second study, HeJ and OuJ mice were injected IP with LP S (10 mu g) and plasma concentration of IL-1 beta was determined posti njection. At 4 h postinjection, the plasma concentration of IL-1 beta was increased by LPS in OuJ mice, but not in HeJ mice. The increase in plasma IL-1 beta in OuJ mice corresponded to the maximal depression i n social behavior. To further verify that HeJ mice are refractory to t he behavioral effects of LPS because they fail to respond and produce cytokines, the social behavior of HeJ and OuJ mice injected IP with re combinant murine IL-1 beta (0, 50, 100, or 200 ng) was compared. As an ticipated, exogenous IL-1 beta depressed social behavior similarly in endotoxin-responsive OuJ mice and endotoxin-resistant HeJ mice. These data indicate that a genetic mutation in HeJ mice that prevents LPS-in duced synthesis of cytokines also renders HeJ mice refractory to the b ehavioral effects of LPS. (C) 1997 Elsevier Science Inc.