[Modulatory effects of taurine on the release of acetylcholine from the central nervous system of an insect, the cockroach (Periplaneta americana L.)].

Taurine, when bath-applied to the sixth abdominal ganglion of the cockroach Periplaneta americana L. produced a reversible dose-dependent blockade of acetylcholine release determined by monitoring excitatory postsynaptic potentials (EPSPs) using the single-fibre oil-gap technique and mannitol-gap technique. The depressant synaptic effect of taurine was not antagonized either with external high calcium concentration or by 4-aminopyridine which is known to increase presynaptic calcium fluxes in other tissues. Inhibition of the taurine blockade by theophylline suggests competition between these molecules in the excitation-secretion coupling. The action of taurine was unaffected by 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1, 1-dioxide hydrochloride (TAG) or bicuculline. The taurine-induced EPSP suppression was reduced by picrotoxin but was unaffected by low chloride saline. The possible mechanisms and sites of taurine action are discussed.