Metabolic aspects of the synthesis and intra‐axonal transport of noradrenaline storage vesicles

Abstract

SUMMARY1. Constricted cat hypogastric nerve/inferior mesenteric ganglion preparations have been maintained for 24 hr in vitro, in either test-tubes or a two compartment box, and used to study the roles of energy metabolism, protein synthesis and calcium ions in the synthesis and transport of noradrenaline storage vesicles in sympathetic neurones.2. When preparations were incubated so that the nerve trunks but not the ganglia were made anoxic, dense-cored vesicles lost their store of noradrenaline and did not accumulate above the ligature. This was accompanied by profound ultrastructural damage to the nerves.3. When in contact with the ligated nerve trunks, sodium fluoride inhibited the intra-axonal movement of dense-cord vesicles but did not deplete them of their stored noradrenaline. When sodium fluoride and pyruvate were present in the medium bathing the nerve trunks the movement of noradrenaline storage vesicles was unaffected.4. Whilst a reduction of the calcium ion concentration in the incubation medium and the inhibition of protein synthesis by cycloheximide prevented the synthesis of dense-cored vesicles in the neuronal perikaryon they had no effect on the movement of preformed dense-cored vesicles along non-myelinated axons.

The role of calcium ions in the synthesis and transport of noradrenaline carrier vesicles in guinea-pig sympathetic neuronsin vitro

“…The present observations on guinea-pig IMG/ligated hypogastric nerve preparations support those of Banks et al (1973) using a similar preparation from cats. Furthermore they substantiate the view that EGTA apparently reduces the amount of material transported from the neuronal perikarya distally along their axons (Banks et aL, 1973;Dravid and Hammerschlag, 1975;Hammerschlag et al, 1975).…”

“…A series of experiments were carried out using colchicine, which is known to inhibit fast axoplasmic transport of DCVs (Banks et al, 1973).…”

“…Furthermore, it has been suggested that calcium ions are required for loading of proteins onto the axoplasmic transport mechanism . Banks et al (1973) found no evidence that free calcium ions were required for the axoplasmic transport of noradrenaline (NA)-containing dense-cored vesicles (DCVs)…”

The EFFECT OF NERVE STIMULATION ON THE AXONAL TRANSPORT OF NORADRENALINE AND DOPAMINE‐β‐HYDROXYLASE

“…If this were so one might expect that changes in intracellular Ca concentration resulting from increased nerve activity could influence the granule-microtubule interaction. However marked changes in Ca concentration in hypogastric nerves in vitro have little effect on granule accumulation (Banks, Mayor & Mraz, 1973). Since minor disruption of microtubule structure is able to influence noradrenaline transport (Banks et al, 1971b) it may be that increases in transport require the formation of increased numbers of microtubules within the axon.…”

The EFFECTS OF THE CALCIUM IONOPHORE, A23187, ON THE AXOPLASMIC TRANSPORT OF DOPAMINE Β‐HYDROXYLASE

“…Since antimitotic agents such as colchicine and vinblastine, which are known to interact with protein subunits of cytoplasmic microtubules (Borisy & Taylor, 1967), inhibit the axoplasmic transport of noradrenaline (Dahlstr6m, 1970;Banks, Mayor, Mitchell & Tomlinson, 1971) it is generally accepted that the axonal microtubular system is probably intimately involved in the process of rapid axoplasmic transport. Recently it has been shown that the transport of adrenergic vesicles involves an active process which requires energy and is greatly influenced by the extracellular concentrations of sodium and potassium ions (Banks, Mayor & Mraz, 1973;Kirpekar, Prat & Wakade, 1973; Garcia, Kirpekar, Prat & Wakade, 0007-1188/80/110375-07 $01.00 1974). In a hypothesis for fast axonal transport, Ochs (1972) suggested the existence of axonal transport filaments, which would slide along microtubules by means of cross-bridges activated by adenosine triphosphate (ATP).…”