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 vari ous brain regions of saline- and kainic acid-treated rats were examine d using in situ hybridization technique. In normal rat brain. the sign als of IL-1beta mRNA were observed in the cerebellar Purkinje cells an d in dispersed cells in the hypothalamus. In the case of the kainic ac id treatment, IL-1beta mRNA was intensely induced in the olfactory bul b, lateral septum, thalamus, hypothalamus, polymorphic layers of hippo campus, piriform cortex, amygdala, entorhinal cortex and cerebral cort ex at 2 h after the injection of kainic acid. In the hypothalamic regi on, we observed the induction of IL-1beta mRNA around the paraventricu lar hypothalamic nucleus, anterior hypothalamic area, dorsomedial and ventromedial hypothalamic nucleus, mammillary regions and arcuate nucl eus. The signal of IL-1beta mRNA was still expressed 4 h after treatme nt 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 gl ial cells, which were densely stained by Cresyl violet and did not con tain glial fibrillary acidic protein. These results suggest that IL-1b eta is produced by a certain type of glial cells, maybe microglia, and might have regulatory functions in the central nervous system.