Conditioned taste aversion but not adrenal activity develops to ICV administration of interleukin-1 in rats.

In a previous investigation with mice, the paired presentation of either odor or taste cues with the peripheral (IP) administration of the immunoactive peptide interleukin-1 (IL-1) led to the conditioned enhancement of glucocorticoid production. The present study found that an initial central infusion of IL-1 in the presence of saccharin cues produced a robust taste aversion but not a conditioned elevation of either ACTH or corticosterone production. These results indicate that the glucocorticoid response induced by centrally administered IL-1 in rats is independent of the behaviorally aversive properties of this cytokine which are conditionable. The differential effects of IP versus ICV administration of IL-1 on glucocorticoid conditioning requires a clearer specification of the respective signaling mechanisms and pathways activated by these two routes of administration.