IS THE INTRASOMAL PHASE OF FAST AXONAL-TRANSPORT DRIVEN BY OSCILLATIONS OF INTRACELLULAR CALCIUM

An hypothesis is presented suggesting that the delivery of vesicle-packaged protein from the neuronal soma to the axonal transport system is physiologically coupled to spontaneous fluctuations of intracellular calcium (Ca-i). Evidence is reviewed that oscillations of Ca-i, commonly detected as agonist- or voltage-triggered waves and spikes propagating through the cytosol, also occur as spontaneous events. Endogenously-generated oscillations are examined since intrasomal transport persists in the absence of extracellular signals or nerve impulse activity. Vesicle budding from the endoplasmic reticulum (ER) may be a key step at which anterograde transport is regulated by events related to the release and reuptake of ER stores of Ca2+.