The relation between pyruvate utilization and acetylcholine synthesis was investigated in minces of adult rat brain. The flux of pyruvate to acetylcholine was less than 1% of that to CO2; nevertheless, a number of agents which inhibited conversion of [1-14C]-pyruvate or [2-14C]pyruvate into 14CO2 were associated with corresponding decreases in the conversion of [2-14C]pyruvate into acetylcholine. The amount of acetylcholine produced by minces of whole rat brain, measured by g.l.c.-mass spectrometry, decreased similarly. Among the inhibitory compounds tested were 3-bromopyruvate, an irreversible inhibitor of pyruvate dehydrogenase; 2-oxobutyrate, a competitive inhibitor of pyruvate dehydrogenase; other 2-oxo acids; and amobarbital and pentobarbital. Linear-regression equations relating CO2 production to acetylcholine synthesis gave correlation coefficients of 0.89-0.93 for the combined observations. The inhibition of acetylcholine synthesis could not be attributed to inhibition of choline acetyltransferase. Incorporation of [2-14C]pyruvate into lipids, proteins and nucleic acids was effected less than that into acetylcholine. Under these experimental conditions, it was shown that pyruvate utilization can limit acetylcholine synthesis.
