Acetylcholine Release at Parasympathetic Synapses

Summary.The submaxillary gland was perfused with eserinized plasma and the perfusate tested for acetylcholine on cat's blood pressure. Small amounts of acetylcholine could always be detected in the venous outflow; during stimulation of the chorda tympani there was an increase in acetylcholine content. When the perfusion fluid contained curare (Intocostrin 10‐4), stimulation of the chorda was also accompanied by an increase in acetylcholine content of the perfusate but only to about a third or a fourth of the value obtained on stimulation without curare. The average output of acetylcholine in ten experiments on cats (two minutes stimulation, 20 shocks/sec.) was 0.144 μg without and 0.050 μg with curare. It is suggested that the acetylcholine obtained in the latter case originated from the parasympathetic nerve endings in the submaxillary ganglion, since it is very unlikely that with this concentration of curare transmission occurs across the ganglion even in the presence of eserine. This assumption is further supported by pharmacological evidence and by the fact that the chorda tympani contains acetylcholine in relatively high concentration.This work was originally planned in discussions with Professor F. C. MACINTOSH, when one of us (N.E.) had the advantage of working with him at the National Institute for Medical Kesearch in London. The authors are greatly indebted to him for these discussions and for his kindness in looking over the manuscript.The investigation has been aided by a grant to one of us (N.E.) from the Swedish Medical Eesearch Council.