Intra-Axonal Transport of Young Amine Granules: Implications for Nerve-Terminal Function

Abstract

In the adrenergic neuron the transmitter noradrenaline (NA) is stored in a special particle, which has been called the amine storage granule (for history and references, see e.g. Iversen, 1967). These amine granules, identified in the electron microscope as dense-core vesicles (for review and references, see e.g. Hokfelt, 1968), accumulate particularly in the varicosities of the nerve terminals, but are also found in the soma and axons. The granules are complex organelles, containing not only NA, but also ATP and the proteins chromogranine and dopamine-β-hydroxylase (DβH) (cf. Lagercrantz, 1971; De Potter et al, 1972). They are formed in the cell body of the neuron, more or less mature, and are rapidly transported distally along the axons towards the nerve terminals — at about 5–10 mm/h in the peripheral adrenergic neuron (for review see e.g. Dahlstrom, 1971; Geffen and Livett, 1971). The transport mechanism is thought to be associated with the axonal microtubules since vinblastine and colchicine, which both disrupt the microtubules can inhibit the proximodistal transport of amine storage particles or granules (cf. Dahlstrom, 1970; Bank et al., 1971).