Some Factors Affecting Catecholamine Uptake, Storage, and Release in Adrenergic Nerve Granules

Some properties of the specific noradrenaline (NA) granules in adrenergic neurons are briefly reviewed. The spontaneous release of NA from splenic nerve granules follows an exponential course, with a half-time of three to four minutes at 37 C and pH 7.5 when NA is continuously removed from the medium by ferricyanide. The difference in release rate between splenic nerve granules, adrenal medullary granules, and granules from the vesicular gland and vas deferens is emphasized.

A continuous reuptake of NA occurs from the medium containing NA. The “protective” effect of ATP is prevented by ferricyanide, and is presumably due to enhanced uptake balancing the normal release.

Radioactive NA in tracer concentrations is taken up to about 30% of the total in the granules in 60 minutes at 20 C in the persence of 10⁻⁶ M NA in the meduim.

The presence of extragranular NA and its possible role in the regulation of synthesis is briefly discussed. Some examples are given of drug actions which may be interpreted by considering the actions on release and reuptake of NA in nerve granules. Release and uptake processes for NA react differently to many drugs, suggesting that they represent different mechanisms. Adrenergic blocking drugs inhibit the uptake of NA from the medium into the granules.