Interleukin (IL)-1beta induces a prolonged hypoglycemia in mice that is not caused by a reduction in food intake and is dissociable from insulin effects. There is a peripheral component in the hypoglycemia that the cytokine induces resulting from an increased glucose uptake, an effect that can be exerted in a paracrine fashion at the site where IL-1 is locally produced. However, the maintenance of hypoglycemia is controlled at brain levels because the blockade of IL-1 receptors in the central nervous system inhibits this effect to a large extent. Furthermore, there is evidence that the cytokine interferes with counter regulation to hypoglycemia. Here we report that administration of IL-1 or long-lasting insulin results in different changes in food intake and in neuroendocrine mechanisms 8 h following induction of the same degree of hypoglycemia (40-45% decrease in glucose blood levels). Insulin, but not IL-1, caused an increase in food intake and an endocrine response that tends to reestablish euglycemia. Conversely, a decrease in noradrenergic and an increase in serotonergic activity in the hypothalamus occur in parallel with a reduction of glucose blood levels only in IL-1-treated mice, effects that can contribute to the maintenance of hypoglycemia. These results are compatible with the proposal that IL-1 acting in the brain can reset glucose homeostasis at a lower level. The biologic significance of this effect is discussed.