Assessment of motor performance decrement following soman poisoning in mice

A simple motor performance test, the inverted screen test, was used to assess the incapacitating effects of soman in mice and to evaluate the effectiveness of carbamate pretreatment and/or treatment with atropine plus 2-PAM on soman-induced debilitation. The test requires minimal equipment and personnel training, and can be done rapidly on untrained animals. Mice were placed individually on wire mesh screens which were horizontally mounted on a metal rod. The rod was rotated 180 degrees so that the mice were oriented upside down on the bottom of the screen. The animals were observed for their ability to climb to the top of the screen within one minute. Mice exhibited significant disruption of performance on the screen test 24 hours after soman doses of 0.71 LD50 or more. Treatment with atropine and 2-PAM i.m. 10 sec post-soman (1.1 x LD50) did not improve screen test performance when measured at 24 hours. Pretreatment with pyridostigmine or physostigmine in combination with post-soman therapy with atropine and 2-PAM significantly improved screen test performance as early as 2 hours after soman. The results suggest that the inverted screen test may be useful as a first-line assessment of the efficacy of pretreatment and treatment compounds against nerve agent-induced incapacitation.