Journal of Neuroscience, Vol 4, 1800-1808, Copyright © 1984 by Society for Neuroscience
Routing of transmitter and other changes in fast axonal transport after transection of one branch of the bifurcate axon of an identified neuron
JM Aletta and DJ Goldberg
The regulation of the quantities and types of organelles that leave the
neuronal cell body destined for use in the axon and its terminals is not
well understood. We had previously found that transport of transmitter
undergoes a precise down regulation when most of one branch of the
bifurcate axon of an identified serotonergic neuron was removed. We have
now investigated further the nature of the regulatory event and the reason
for its initiation by eliminating portions of the axonal tree of this
neuron. We find that the down regulation is more likely to be due to the
loss of synapses than of axon because transport of [3H]serotonin decreases
as much when an axonal branch is transected distally as after a proximal
transection. Transport of [3H]fucosyl glycoprotein, which normally is
associated with the serotonergic vesicle in this axon, decreases to the
same extent as transport of [3H]serotonin following proximal transection.
The glycoprotein down regulation occurs much more rapidly, possibly due to
an inhibition of vesicle synthesis. A secondary rise in transport of [3H]
fucosyl glycoprotein 3 days to 2 weeks after axotomy suggests that the
radiolabeled glycoprotein has undergone a redistribution into organelles
not normally labeled and transported in intact neurons in large amounts,
since [3H]serotonin transport remains stably diminished during this period.
We also describe here a case of routing of rapidly transported material.
When one axonal branch is cut far from the point of bifurcation
(approximately 10 mm), [3H]serotonin is directed away from the ranch
lacking its synaptic terminals and into the remaining intact branch even
though the transected branch is physically capable of transporting its
normal amount of [3H]serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)