Walker_1976_Neurosci_1_509

Previous studies have established that short treatments with diisoprophylphosphorofluoridate of chick embryo muscle cultures irreversibly inhibit the enzyme acetylcholinesterase and that the enzyme's levels in the cells rapidly recover due to synthesis of new protein. In addition, it has been shown that acetylcholine, acetyl-beta-methylcholine and choline increase the acetylcholinesterase content of the cultures. In the experiments presented here, actinomycin D and cycloheximide were used to study the relationships between the synthesis of ribonucleic acid and of protein, the recovery of acetylcholinesterase levels after diisopropylphosphorofluoridate treatment and the increase of acetylcholinesterase levels evoked by choline and its esters. Both recovery of acetylcholinesterase and the increase in its activity with acetyl-beta-methylcholine occurred in the absence of ribonucleic acid synthesis but required protein synthesis. The results suggest that transcription of desoxyribonucleic acid and a change in the degradation rate of acetylcholinesterase are not involved. An additional finding was that the level of newly synthesized acetylcholinesterase activity continued to increase for a short period of time after synthesis of protein had ceased, as if some previously synthesized protein was being transformed into active enzyme.