Role of the central opioid system in the inhibition of water and salt intake induced by central administration of IL-1β in rats

In the present study we investigated, the effect of third ventricle injections of IL-1β on water and salt intake in fluid-deprived and sodium-depleted rats. Central administration of IL-1β significantly reduced water and salt intake in fluid-deprived animals and decreased salt intake in sodium-depleted rats. The antidipsogenic and antinatriorexic effects elicited by the central administration of IL-1β were suppressed by pretreatment with central injections of the non-selective opioid antagonist naloxone (10 μg) in the two different experimental protocols used here (water deprivation and sodium depletion). In addition, central administration of IL-1β failed to modify the intake of a 0.1% saccharin solution when the animals were submitted to a “dessert test” or to induce any significant locomotor deficit in the open-field test. The present results suggest that the activation of the central interleukinergic component by IL-1β impairs the increase in water and salt intake induced by water deprivation and the enhancement in sodium appetite that follows sodium depletion. The data also support the conclusion that the antidipsogenic and antinatriorexic effects resulting from the activation of the central interleukinergic component rely on an opioid-dependent, naloxone-blockable system.