ORGANOPHOSPHATE INHIBITORS OF ACETYLCHOLINE-RECEPTOR AND ACETYLCHOLINE ESTERASE TESTED ON ELECTROPLAX

The organophosphates-DFP, phospholine, and Paraoxon, long known to be potent inhibitors of acetylcholine (AcCh)-esterase-have been applied to the monocellular electroplax preparation. The experiments show that the compounds act at high concentrations as inhibitors of the AcCh-receptor. The effects are rapidly reversible. At low concentrations the organophosphates potentiate the action of AcCh. Occasionally they may cause spontaneous depolarizations of the electroplax membrane. These effects are due to the inhibition of AcCh-esterase, since they are rapidly reversed by pyridine-2-aldoxime methiodide, a potent and specific reactivator of phosphorylated enzyme. A reversal takes place also in Ringer's solution, but much more slowly. Ambenonium, a bisquaternary nitrogen derivative and a potent inhibitor of AcCh-esterase, also causes spontaneous depolarizations. It potentiates the action of AcCh, but to a lesser extent than the organophosphates. © 1969.