Two rates of fast axonal transport of [3H]glycoprotein in an identified invertebrate neuron.

Recently, the kinetics of fast axonal transport of a single type of organelle, the serotonergic storage vesicle, was described in an identified axon of Aplysia using a pulsing technique combined with intracellular injection of [3H]serotonin. Here we extended the single axon studies by analyzing the movement of pulses of [3H]glycoprotein, following injection into the giant Aplysia cell, R2, of the amino sugar [3H]N-acetylgalactosamine. This glycoprotein precursor has been shown to label several organelles in this neuron. [3H]Glycoprotein is found to move in the axon of R2 at 2 rates of fast transport, 174 and 105 mm per day at room temperature. We suggest that the 2 rates reflect movements of 2 different types of organelle.