MAPPING OF CORTICAL METABOLIC-ACTIVATION IN SOMAN-INDUCED CONVULSIONSIN RATS

The metabolic activation of the cerebral cortex during convulsions ind uced by the organophosphorus cholinesterase inhibitor soman was studie d in detail. Soman was given at a dose equivalent to 0.9 LD50 (100 mu g/kg SC after pretreatment with 26 mu g/kg pyridostigmine, IM, to decr ease lethality) to examine separately the metabolic effects of severe acetylcholinesterase inhibition, present always with this dose, and co nvulsions, present only in some of the animals, Cerebral glucose utili zation (CGU) values of cortex divided by CGU of brain stem (nCGU) were calculated for 96 locations in nine coronal slices. Animals injected with pyridostigmine-soman and that developed convulsions (n = 7) showe d statistically significant increases of nCGU with regard to animals i njected with saline (n = 5) in 33 locations, 27 of which were in a sin gle cluster, with the piriform cortex at its center, Perirhinal cortex , and insular cortex also showed significantly higher nCGU in convulsi ng rats, Other foci of elevated nCGU were found in frontal and parieta l locations, In animals injected with pyridostigmine-soman and that di d not develop convulsions (n = 5) in spite of severe cholinesterase in hibition, a single location (piriform cortex) showed significantly hig her nCGU than controls, Neuropathology evaluation showed a significant decrease in viable cells only in animals that developed convulsions, This effect correlated with enhanced nCGU. It is concluded that the pr esence of convulsions, and not exposure to pyridostigmine-soman, deter mined the pattern of nCGU cortical activation, which correlated closel y with the structural changes. (C) 1997 Elsevier Science Inc.