Use of differentiated cholinergic and second messenger endpoints to evaluate cholinesterase inhibitors.

1. The effects of organophosphorus compounds on the cholinergic properties of a mouse septal neuronal cell line, SN56, were investigated. Treatment of the cells with 10 mumol/L paraoxon or 10 mumol/L diisopropylphosphorofluoridate (DFP) resulted, respectively, in rapid 27- and 11-fold increases of intracellular acetylcholine content. 2. Time-course studies showed that paraoxon maintained its efficacy whereas the effects of DFP decayed quickly, possibly due to rapid hydrolysis and inactivation of DFP in the growth medium.