OXYGEN-FREE RADICALS IN RAT LIMBIC STRUCTURES AFTER KAINATE-INDUCED SEIZURES

Several indices of free radical generation were determined in limbic s tructures after kainate (KA)-induced seizure activity in adult and pos tnatal day (PND) 12 and 17 rats. Superoxide dismutase, catalase, and g lutathione peroxidase activities were measured in piriform cortex and hippocampal subfields at 8, 16, 48 h, and 5 days after KA injection in adults and pups, and also at 3 weeks postinjection in adults. KA-indu ced seizure activity had no significant effect on enzyme activities in PND 12 and 17 rats. In adults, superoxide dismutase and catalase acti vities were significantly increased at 5 days after KA administration, and returned to preinjection levels by 3 weeks. Glutathione peroxidas e activity was also increased significantly at 5 days postinjection, b ut remained elevated at 3 weeks. Lipid peroxidation, as indicated by m alondialdehyde (MDA) concentration, exhibited an early significant inc rease at 8 and 16 h, followed at 48 h and 5 days by a significant decr ease. At 3 weeks postinjection, MDA levels were still significantly de creased in CA3 and dentate gyrus. KA administration in PND 12 and 17 r ats had no significant effect on MDA content. KA-induced seizure activ ity in adults also resulted in a large and sustained increase in prote in oxidation in piriform cortex and hippocampus. The early increase in MDA and protein oxidation in adult rats strongly suggests the involve ment of oxygen free radicals in the initial phases of KA-induced patho logy, whereas the changes in scavenging enzyme activities and MDA cont ent at 5 days and 3 weeks post KA injection possibly reflect glial pro liferation subsequent to neuronal death.