Anorexic But Not Pyrogenic Actions of Interleukin‐1 are Modulated by Central Melanocortin‐3/4 Receptors in the Rat

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Abstract
The cytokine interleukin-1 (IL-1), which mediates many responses to infection and injury, induces anorexia and fever through direct actions in the central nervous system. The melanocortin neuropeptides, such as alpha melanocyte-stimulating hormone (α-MSH), reportedly antagonize many actions of IL-1, including fever and anorexia. However, it is unknown whether endogenous melanocortins modulate anorexia induced by IL-1. The objective of the present study was to establish the effect of endogenous melanocortins on IL-1-induced anorexia and fever in the rat. Intracerebroventricular (i.c.v.) injection of IL-1β caused a significant reduction in food intake and body weight gain, and a rise in core body temperature in conscious rats. Coadministration of the melanocortin-3/4 receptor (MC3/4-R) antagonist, SHU9119, reversed IL-1β-induced reductions in food intake and body weight, but did not affect the febrile response to IL-1β. These data suggest IL-1β may elicit its effects on food intake through the melanocortin system, predominantly via the MC3-R or MC4-R. In contrast, IL-1β-induced fever does not appear to be mediated or modulated by MC3-R or MC4-R activity.