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

We examined whether central or peripheral administration of interleukin-1beta (IL-1beta) 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-1beta into the mPFC resulted in dose-dependent increases in levels of both NOx(-) and 2,3-DHBA. In contrast, peripheral administration of IL-1beta significantly increased NOx(-) levels but not 2,3-DHBA levels. Perfusion of Mn(III) tetrakis (4-benzoic acid) porphyrin chloride, a superoxide (O(2)(-)) dismutase mimic, into the mPFC reduced the increases in levels of 2,3-DHBA induced by centrally administered IL-1beta, but enhanced the increases in levels of NOx(-) induced by centrally administered IL-1beta. The present results show a different response in free radical productions in the mPFC between central and peripheral administration of IL-1beta. This finding should be useful for our understanding of the response of NO and free radicals such as *OH and O(2)(-) in the mPFC after central and peripheral administration of IL-1beta.