Reactivation of Cyclosarin-inhibited Rat Brain Acetylcholinesterase by Pyridinium-Oximes

Cyclohexyl methylphosphonofluoridate (cyclosarin, cyclosin, GF) is a highly toxic organophosphate, which is resistant to conventional oxime therapy. To gain insight into the reactivation kinetics, rat brain acetylcholinesterase (AChE) was inhibited in vitro by cyclosarin (pH 8.0, 25°C) and reactivated with 22 different pyridinium-oximes. Three compounds were shown to be superior to the other oximes: 4-carbamoyl-4′-[(hydroxyimino)methyl]-1,1′-(oxydimethylene)dipyridin-1-ium dichloride (HS-6), 4′-carbamoyl-2-[(hydroxyimino)methyl]-1,1′-(oxydimethylene)dipyridin-1-ium dichloride (HI-6), and 4′-carbamoyl-2-[(hydroxyimino)methyl]-1,1′-(but-2-ene-1,4-diyl)dipyridin-1-ium dichloride (BI-6).