INDUCTION OF INTERLEUKIN-1-BETA MESSENGER-RNA AFTER FOCAL CEREBRAL-ISCHEMIA IN THE RAT

The expression of interleukin-1beta (IL-1beta) mRNA in the brain in re sponse to cerebral ischaemia in rats was examined using in situ hybrid ization histochemistry. Focal cerebral ischaemia was induced in sponta neously hypertensive rats by permanent occlusion of the left middle ce rebral artery (MCAO). Whereas no IL-1beta mRNA could be detected in no n-operated and sham-operated rats, middle cerebral artery occlusion in duced the expression of IL-1beta mRNA within 15 min in the ischaemic b rain regions prone to become necrotic after 1-2 days. The message appe ared as spot-like signals, reached a peak after 3 h and then declined to undetectable levels within 4 days. Additionally, a pronounced but b rief induction of IL-1beta mRNA could be detected 1 h after MCAO in th e meninges near the watershed zone. The results demonstrate that the i nflammatory cytokine IL-1beta is induced in a time-dependent way after brain ischaemia.