SYSTEMIC KAINIC ACID INJECTION STIMULATES EXPRESSION OF HIGHLY POLYSIALYLATED NEURAL CELL-ADHESION MOLECULES IN REACTIVE ASTROCYTES OF THE ADULT-RAT HIPPOCAMPUS

In order to study the mechanism of status epilepticus, we have analyze d neurochemical changes in the rat hippocampus following injection of kainic acid (KA), a glutamate receptor agonist. Subcutaneous administr ation of KA to the rat induced neuron death, reactive gliosis and spro uting of mossy fibers in the hippocampus. At 4 days after the KA treat ment, the neuronal degeneration and death occurred especially in CAI a nd hilus of dentate gyrus, simultaneously with a remarkable increase i n reactive astrocytes rich in glial fibrillary acidic protein (GFAP). By using a double staining technique, we found that some of the GFAP-p ositive reactive astrocytes also expressed highly polysialylated neura l cell adhesion molecules (NCAM-H). We also observed in the molecular layer of dentate gyrus, a significant increase of reactive astrocytes with NCAM-H and sproutings of the mossy fibers. Our observations clear ly suggest that the reactive astrocytes, expressing NCAM-H, play an im portant role in the sprouting of the mossy fibers to the inner molecul ar layer of the hippocampus after systemic KA injection.