Effects of diacylglycerol and phorbol ester on acetylcholine release and action at the neuromuscular junction in mice.

Miniature endplate potentials and nerve-evoked endplate potentials were studied in a phrenic nerve-diaphragm preparation of the mouse. A phorbol ester, phorbol-12 beta, 13 alpha-dibutyrate, and a diacylglycerol, 1-oleyl-2-acetyl-sn-glycerol, both increased the frequency of miniature endplate potentials. The effect of the phorbol ester on the frequency was still significant when the preparation was incubated in a calcium-deficient solution. The phorbol ester, but not the diacylglycerol, caused a significant increase in the amplitude of the miniature potentials. The phorbol ester also increased the amplitude of the endplate potentials in the presence of (+)-tubocurarine. The mechanisms of action of phorbol ester and diacylglycerol are discussed in relation to the control of acetylcholine release and action at the neuromuscular junction.