Release of endogenous acetylcholine from rat brain slices with or without cholinesterase inhibition and its potentiation by hemicholinium-3.

The direct measurement of basal and high K(+)-stimulated release of endogenous acetylcholine from striatum and hippocampus slices was achieved without as well as with a cholinesterase inhibitor, physostigmine. Hemicholinium-3, opposite to its well-known activity as an inhibitor of endogenous acetylcholine release, significantly potentiated both the basal and stimulated release, in particular in the absence of physostigmine, suggesting an involvement of some unknown activity stimulating ACh release in hemicholinium-3.