SOME EFFECTS OF SOMAN ON NEUROMUSCULAR FUNCTION AND ON ACETYLCHOLINESTERASE IN THE RAT

¹ Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington

The effect of soman (methyl pinacolyl phosphonofluoridate) on indirectly induced isotonic and isometric twitch response of intact anterior tibial muscle of atropinized and artificially respired rats was studied. Small doses (0.02 to 0.08 mg/kg) produced potentiation of the twitch and larger doses produced some inhibition of the twitch; however, neuromuscular function continued to be present following total doses of soman of 40 mg/kg (2000 times greater than the minimal effective doses and 700 times greater than the LD5O). Acetylcholinesterase activity of muscle homogenates from animals treated with soman indicates that soman is a potent inhibitor of this enzyme and that no AChE activity was measurable in the muscle homogenates from animals pretreated with doses of soman of 0.06 to 0.1 mg/kg. In intact chronically denervated anterior tibial muscle preparations, soman did not produce potentiation of the directly induced twitch response, rather it produced a "slow contraction" of the muscle upon which the twitch responses were superimposed.