Abstract
On comparing the secretion of noradrenaline (NA) evoked by electrical field stimulation of the ‘short’ adrenergic nerves of guinea‐pig isolated vas deferens (Sjöstrand 1962) with that evoked by similar stimulation of the ‘long’ adrenergic nerves of human isolated omental blood vessels, using identical experimental conditions, it was found that the two types of nerve differ markedly in ‘secretory excitability’. While it was possible to adjust the strength and/or duration of stimulus shocks to a level causing a well‐defined maximum in 3H‐NA output from the human vasomotor nerves, no such ‘supramaximal’ level could be reached in the nerves of guinea‐pig vas deferens.