The cytokine interleukin-1 (IL-1) appears to play a pivotal
role in the orchestration of brain-mediated, nonspecific illness
symptoms during an infection. In the present study, we examine
the possibility that IL-1 is produced in the central nervous
system itself, which may be responsible for the induction of
brain-mediated responses. Using immunocytochemical techniques,
we demonstrated that peripheral administration of bacterial
endotoxin to rats caused a time- (1.5-24 hr) and dose-dependent
(4µg/kg-2.5 mg/kg) induction of IL 1ß immunoreactivity
in cells identified as macrophages in meninges and choroid plexus
and microglial cells in various brain regions. At 8 hr after
endotoxin (2.5 mg/kg), immunoreactive IL-1
was observed in the
same areas and cell types as IL-1ß. Although no quantitative
measurements have been performed, it appears that fewer cells
express immunoreactive IL-1
than IL-1ß. Furthermore,
IL-1ra was found to be constitutively expressed in neurons in
the paraventricular nucleus and supraoptic nucleus, which is
in accordance with mRNA data. After administration of endotoxin,
we observed no additional cells that expressed immunoreactive
IL-1ra. We conclude that IL-l
and IL-1ß production
in the brain is induced in the same cell types, whereas IL-lra
is expressed consititutively by a different cell type-probably
neurons.
, ß, and Receptor Antagonist in Rat Brain
