Induction of NO synthase and glial acidic fibrillary protein in astrocytes in the temporal cortex of the rat with audiogenic epileptiform reactions.

The localizations of NADPH-diaphorase (NADPH-d), inducible NO synthase (iNOS), and glial acid fibrillary protein (GFAP) in astrocytes of the temporal cortex were studied in Krushinskii-Molodkina rats, which are genetically predisposed to audiogenic convulsive seizures. Convulsive reactions were induced in rats by three exposures to acoustic stimuli. Controls consisted of Wistar rats and Krushinskii-Molodkina rats not subjected to acoustic stimulation, these not developing convulsive reactions. The neocortex of animals with audiogenic convulsions consistently showed foci of brain tissue damage. Foci, of diameter 300-400 microm, were located in layers III-V and were groupings of NADPH-d-positive astrocytes; these were seen in both hemispheres. Astrocytes in foci of damage expressed iNOS and had elevated GFAP levels. The numbers of GFAP-immunopositive cells were increased by 25-37% in damage foci as compared with levels in controls and undamaged areas of the cortex. The induction of NO synthase and GFAP in astrocytes seen here indicates the involvement of glia in compensatory NO-dependent mechanisms formed in damage foci in response to audiogenic convulsive seizures.