Toxicity of soman after repetitive injection of sublethal doses in rat

Injection of sublethal doses of soman in rat intraperitoneally or subcutaneously every 4, 8, 12 or 24 hours led to chronic LD50 doses which were markedly higher than the acute one. When rats were exposed every 24 hrs to half LD50 doses of soman, several of the animals did not show symptoms of soman poisoning and survived a total exposure of 4-7 times the acute LD50 dose. Brain and diaphragm acetylcholinesterase activities declined steadily during the chronic soman exposure. The so-called external acetylcholinesterase activity of the diaphragm was inhibited to a slightly less degree than the total acetylcholinesterase of the same tissue. The ability of the liver to hydrolyze soman was similar in rats which survived several 24 hr doses and untreated rats.