IN-SITU HYBRIDIZATION STUDY OF INTERLEUKIN-1-BETA MESSENGER-RNA INDUCED BY KAINIC ACID IN THE RAT-BRAIN

The distribution patterns of interleukin-1beta (IL-1beta) mRNA in various brain regions of saline- and kainic acid-treated rats were examined using in situ hybridization technique. In normal rat brain. the signals of IL-1beta mRNA were observed in the cerebellar Purkinje cells and in dispersed cells in the hypothalamus. In the case of the kainic acid treatment, IL-1beta mRNA was intensely induced in the olfactory bulb, lateral septum, thalamus, hypothalamus, polymorphic layers of hippocampus, piriform cortex, amygdala, entorhinal cortex and cerebral cortex at 2 h after the injection of kainic acid. In the hypothalamic region, we observed the induction of IL-1beta mRNA around the paraventricular hypothalamic nucleus, anterior hypothalamic area, dorsomedial and ventromedial hypothalamic nucleus, mammillary regions and arcuate nucleus. The signal of IL-1beta mRNA was still expressed 4 h after treatment with kainic acid, less intensely than at 2 h, but above the control level. In these regions, IL-1beta mRNA was expressed mainly in the glial cells, which were densely stained by Cresyl violet and did not contain glial fibrillary acidic protein. These results suggest that IL-1beta is produced by a certain type of glial cells, maybe microglia, and might have regulatory functions in the central nervous system.