THE noradrenaline (NA) content of sympathetically innervated organs remains remarkably constant, at a concentration characteristic of each individual organ, during widely varying states of nerve activity1. Because an increase in the frequency of nerve impulses is associated with an increased loss of NA from the neurone, its capacity to maintain an essentially unchanged NA content has been regarded as evidence that the synthesis of NA is accelerated by nerve activity1. The opposite view—that the synthesis of NA in the neurone proceeds at a constant “supramaximal” rate, independent of activity—has, however, also been proposed2,3.