ACETYLCHOLINESTERASE TURNOVER IN BRAIN, CEREBROSPINAL FLUID AND PLASMA

—By assay of acetylcholine hydrolysis to measure total cholinesterase activity and acetyl-β-methylcholine hydrolysis to measure acetylcholinesterase (E.C 3.1.1.7) activity, patterns of regeneration of enzyme activity were measured in seven areas of brain, cerebrospinal fluid and plasma of cats after administration of an irreversible inhibitor. Halftimes of recovery of total cholinesterase in the brain tissues ranged from 0·9 to 3·8 days (av = 2·5 days) and acetylcholinesterase recovery halftimes ranged from 1·2 to 5·3 days (av = 3·6 days). Regeneration of total cholinesterase was also followed in subcellular fractions of guinea-pig and rat brains after similar inhibition. In both species, the fastest recovery occurred in the soluble fraction with halftimes of 1·8 and 1·6 days, while the synaptosomal fractions exhibited the slowest recoveries with halftimes of 8·3 and 4·1 days. Regeneration of activity in plasma and CSF most nearly resembled that of the soluble brain fraction.