Increased expression of interleukin-1β in mouse hippocampus after global cerebral ischemia

We examined the in vivo expression of IL-1 beta and its transcript after cerebral ischemia produced in mice cardiac arrest model. The IL-1 beta mRNA in the hippocampal region reached a detectable level at 1 hr after ischemia and had a peak at 3 hr after ischemia recirculation. But it was markedly decreased at 1 day and reached the control levels at 4 day after ischemia recirculation. The IL-1 beta -like immunoreactivity was observed at 1, 2, 4 day after ischemia recirculation and its immunoreactivity was detected at 2 day. The IL-1 beta -like immunoreactivity was observed in both microglia and astrocytes after bran ischemia by double immunostaining. These results provide the direct evidence for the localization and induction of IL-1 beta expression in vivo in mice after ischemia. It is suggested that IL-1 beta, produced in both astrocytes and microglia cells after ischemia, directly affect on neurons as well as glial cells to induce delayed neuronal cell death.