ACTION SUBSTANCES OF PERIPHERAL-NERVE REVISITED

Fifty years ago, four 'action substances' were described as being 'lib erated' from peripheral nerve in the course of activity. An attempt ha s been made to update this information. Confirmatory evidence is avail able that acetylcholine and thiamine do play a role in the course of a ctivity. However, the question of the relationship in time between the ir release and the electrical events, and the possible effect on speci fic ionic gating mechanisms, remains unclarified. The 'liberation' of potassium has been found to be a transmembrane K efflux, and the quest ion of the existence of another substance similar to thiamine has not been pursued.