Acute exposure to a low or mild dose of soman: biochemical, behavioral and histopathological effects

Effects of low to mild doses of soman on central and blood cholinesterase (ChE) activities and anxiety behavior were studied in mice 30 min, 24 h and 7 days after poisoning. At these two latter time points, histopathological consequences of soman intoxication were also studied. The 30-microg/kg dose of soman produced 30 min after intoxication, about 35% of central ChE inhibition, and an anxiolytic effect without toxic signs or histopathological changes. The 50-microg/kg dose of soman produced at the same time, about 56% of central ChE inhibition, slight clinical signs of poisoning without convulsions, an anxiogenic effect with a slight hypolocomotion but no brain damage. A mild dose of soman (90 microg/kg) produced at this same time point about 80% of central ChE inhibition, and led to ataxia and tremors in every mouse and to convulsions in some of them. Thirty minutes and 24 h after poisoning, the behavioral tests revealed neither anxiolytic nor anxiogenic responses despite a clear hypolocomotion. Only mice that experienced long-lasting convulsions developed neuropathological changes. The functional implication of our results, as well as the biological relevance of blood vs. brain ChE levels, as an index of intoxication severity are discussed.