Microanalysis of endogenous acetylcholine released from the hemidiaphragm of the rat

A chemiluminescence method for the determination of endogenous acetylcholine was adapted to transmitter released from the hemidiaphragm of the rat. Released choline and acetylcholine were isolated and concentrated using KI3 precipitation. Between 1 and 20 pmol of acetylcholine may be measured without sample dilution. The detection limit for acetylcholine luminescence is 1.0 pmol; thus, with an observed precipitation recovery of approximately 30%, the lowest detectable released amount is 3.5 pmol. The limitations of the method are discussed.