The Location of Cholinesterase in the Central Nervous System

The oil/water distribution coefficients of a number of cholin‐esterase inhibitors have been obtained. 2. The inhibition of cholinesterase in the brain of dogs has been measured after injection of TEPP and 3‐di iso propylphosphato‐N‐methyl pyridinium methyl sulphate (PPS) both systemically and intracranially. 3. PPS is almost insoluble in lipoid and produces no physiological effects on the central nervous system. 4. Less than lethal doses of PPS produced only 16 per cent inhibition of cholinesterase in grey and white matter. 5. Cholinesterase in a sympathetic ganglion is freely inhibited by PPS. 6. The way in which anticholinesterase drugs produce their central effects is discussed. 7. It is probable that cholinesterase is located at different sites in neuromuscular, sympathetic, and central synapses.