Different response between production of free radicals induced by central and peripheral administration of interleukin-1β in conscious rats

We examined whether central or peripheral administration of interleukin-1β (IL-1β) might change levels of nitric oxide (NO) and hydroxyl radical (OH) in the medial prefrontal cortex (mPFC). Extracellular levels of NO metabolites (NOx−) and 2,3-dihydroxybenzoic acid (2,3-DHBA), as a marker of OH production, were determined with an in vivo microdialysis technique in conscious rats. In the mPFC, central administration of IL-1β into the mPFC resulted in dose-dependent increases in levels of both NOx− and 2,3-DHBA. In contrast, peripheral administration of IL-1β significantly increased NOx− levels but not 2,3-DHBA levels. Perfusion of Mn(III) tetrakis (4-benzoic acid) porphyrin chloride, a superoxide (O2−) dismutase mimic, into the mPFC reduced the increases in levels of 2,3-DHBA induced by centrally administered IL-1β, but enhanced the increases in levels of NOx− induced by centrally administered IL-1β. The present results show a different response in free radical productions in the mPFC between central and peripheral administration of IL-1β. This finding should be useful for our understanding of the response of NO and free radicals such as OH and O2− in the mPFC after central and peripheral administration of IL-1β.