Prolonged and concomitant induction of astroglial immunoreactivity of interleukin-1beta and interleukin-6 in the rat hippocampus after transient global ischemia.

We have investigated the pattern of expression of IL-1beta and IL-6 immunoreactivities in rat hippocampus after transient complete brain ischemia evoked by a 10 min cardiac arrest, at survival times ranging from 1 day to 28 days. To identify the cell types expressing the two immunoreactivities we used specific cell markers and combined staining procedures. In the intact brain IL-1beta and IL-6 were mainly localized in neurons particularly in pyramidal and granular cell layers. Ischemic insult resulted in a concomitant induction of IL-1beta and IL-6 immunoreactivities in multiple astroglia especially in the CA1 area which is the most vulnerable to ischemic insult as manifested by a massive delayed neuronal death accompanied by an intense gliosis. The number of astroglia expressing both immunoreactivities and the intensity of staining was maximal at the 14th day and remained at the same level at the 28th day. Our data suggest that the astroglial IL-1beta and IL-6 may affect the neurodegeneration of CA1 neurons in the ischemic hippocampus and that the prolonged proinflammatory effects of IL-1beta prevail over the presumed protective action of IL-6.