SYNERGISTIC ACTION OF CORTICOSTERONE ON KAINIC ACID-INDUCED ELECTROPHYSIOLOGICAL ALTERATIONS IN THE HIPPOCAMPUS

The present study investigates the effect of overexposure to high dose s of the stress hormone corticosterone (CORT) on the electrophysiologi cal changes produced in the hippocampus after local microinjection of KA. Extracellular recordings were performed in the CA1 area of mouse h ippocampal slices prepared after a 7-day recovery period following KA microinfusion alone or combined with 3 days overexposure to CORT. The results showed that CORT shifts the KA response profile approximately 40-fold, since animals treated with a non-toxic dose of 0.01 mu g KA a nd CORT exhibited epileptic activity and a shift on the paired-pulse r esponse similar to that observed in animals treated with high doses of KA (0.4 mu g). This synergistic action of CORT on the electrophysiolo gical changes induced by KA was antagonized by the antiglucocorticoid RU486 whereas the antimineralocorticoid spironolactone was ineffective . These results suggest that CORT may play an important role in modula ting the severity of KA-induced seizures in the hippocampal structure probably by GR-receptor mediated action.