INTERLEUKIN-1-BETA INCREASES 5-HYDROXYINDOLEACETIC ACID RELEASE IN THE HYPOTHALAMUS INVIVO

Push-pull perfusion technique was used to infuse interleukin-1beta (IL -1beta) into and collect perfusate from the medial basal hypothalamus (MBH) of conscious, freely moving rats. The serotonin metabolite, 5-hy droxyindoleacetic acid (5-HIAA), was measured in the perfusate by high performance liquid chromatography. Infusion of the vehicle, PBS-0.1%B SA, had no significant effect on 5-HIAA release except near the end of the perfusion period (325 min) when the release was below the pretrea tment level (p < 0.05). Infusion of 25 ng of IL-1beta prevented this d ecrease, whereas infusion of 50 ng produced an increase of more than 5 0% (p < 0.05) at 25 min and maintained it at that level during the rem aining posttreatment period. In the animals infused with 100 ng of IL- 1beta, 5-HIAA release increased by more than 70% at 25 min and was mor e than 120% (p < 0.05) above the pretreatment level at the end of the posttreatment period. We concluded that IL-1beta affects the metabolis m of serotonergic system in the hypothalamus and that this is a compon ent of the mechanism by which IL-1 produces its central actions.