EFFECT OF DI-ISOPROPYL FLUORPHOSPHATE (DFP) ON ACTION POTENTIAL AND CHOLINESTERASE OF NERVE. IV

Publisher Website
Google Scholar
Abstract
A great variety of facts showed that the abolition of the action potential by DFP is due to the inactivation of cholinesterase. The concn. of DFP required to abolish conduction in isolated nerves exposed to the compound is about 1 to 2 mg./ml. Since a concn. of DFP in vitro necessary to inactivate comparable amts. of cholinesterase is only a few [gamma]/ml., some investigators consider this discrepancy as evidence that the abolition of conduction by DFP is not due to the inactivation of cholinesterase but to an unknown general toxic effect. The outside concn., however, does not give any indication of the concn. at the site of action. In the observations reported in the paper, it is shown that at the moment that the action potential disappears, only a small fraction of the outside concn. of DFP is found in the interior of the axon. The DFP concn. in the axoplasm of the squid extruded at the time the action potential disappears is usually less than 50% of the outside concn. Recent reports (Boyarski, Tobias and Gerard) that conduction in frog sciatic nerve is still possible after complete inactivation of cholinesterase were reexamined. It was shown that these observations are based on inadequate technique and previous statements that conduction is inseparably associated with cholinesterase activity are confirmed.