In vivo and in vitro inhibition of cholinesterase by methyl-1 (S methyl phosphoryl-3) imidazolium (MSPI), a model of an "instantly" aged phosphorylated enzyme.

Methyl-1 (S-methylphosphoryl-3) imidazolium (MSPI) was approximately equipotent with DFP in producing in mice a lethal intoxication and in inhibiting in vitro cholinesterases of electric-eel, brain and plasma mice. In vivo, a lethal dose of MSPI inhibited plasma but not brain ChE. The intoxication by MSPI was not cured by the combination of Atropine and TMB4 or of diazepam with Atropine and (or) TMB4 and the cholinesterase inhibition was not reversed by TMB4 in vivo nor in vitro in the conditions where DPF intoxication or Che inhibition were.