Specificity of interleukin–1β-induced changes in monoamine concentrations in hypothalamic nuclei: blockade by interleukin-1 receptor antagonist

The purpose of this study was to examine specificity in the effects of interleukin-1β (IL-1β) on monoamines in various areas of the hypothalamus. Adult male rats were injected i.p. with saline or 2.5 or 5.0 μg of IL-1β or were pretreated with 500 μg of IL-1 receptor antagonist (IL-1ra) followed 5 min later by 5 μg of IL-1β. The paraventricular nucleus (PVN), arcuate nucleus (AN), median eminence (ME), and medial preoptic area (MPA) were microdissected and analyzed for neurotransmitter concentrations by high-performance liquid chromatography with electrochemical detection (HPLC-EC). In the PVN, IL treatment produced significant increases in the concentrations of norepinephrine (NE), dopamine (DA), DA metabolite dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), and its metabolite 5-hydroxyindoleacetic acid (5-HIAA). IL-1 treatment increased the concentrations of NE and DA in the AN but only of NE in the ME, and it was without any effect in the MPA. Pretreatment with IL-1ra completely blocked the IL-1 effects. It is concluded that IL-1 induces highly specific changes in monoamine metabolism in the hypothalamus, and the nature of these changes depends on specific hypothalamic nuclei.