ORIGINAL ARTICLE: Evaluation of miosis, behavior and cholinesterase inhibition from low‐level, whole‐body vapor exposure to soman in African green monkeys (Chlorocebus sabeus)*

Abstract

Relatively little is known about the effects of very low-level exposures to nerve agents where few signs or symptoms are present. African green monkeys (Chlorocebus sabeus) (n = 8) were exposed for 10 min, whole-body, to a single concentration of soman (0.028-0.891 mg/m³). EC₅₀ values for miosis were determined to be 0.055 mg/m³ and 0.132 mg/m³ when defined as a 50 percent reduction in pupil area and diameter, respectively. In general, performance on a serial probe recognition task remained unchanged at lower concentrations, but responding was suppressed at the largest concentration tested. Soman produced concentration-dependent inhibition of acetylcholinesterase activity and, to a lesser extent, butyrylcholinesterase activity. These results characterize threshold soman exposure concentrations that produce miosis in the absence of other overt signs of toxicity and extend previous studies indicating that miosis is a valuable early indicator for the detection of soman vapor exposure.