| Neurotransmitter secretion from the nerve terminal
is mediated by the fusion of synaptic vesicles with the plasma membrane.
It is generally believed that neurotransmitter release in mature synapses
is localized to the presynaptic nerve terminals. To probe the topology of
neurotransmitter secretion along developing axons in culture, we recorded
membrane currents from myocytes manipulated into contact with axons. We
have used an electrophysiological technique for the detection of individual
ACh secretion events to characterize ACh secretion along growing Xenopus
axons in culture. The main finding of the present study is that, at the
early stage of axonal growth, ACh release from the neuron takes place along
the axon, as well as at the growth cone (Antonov
et al., 1999). At the later stages of growth, the exocytotic activity
is preferentially localized to the distal axonal region. To our knowledge,
this is the first semiquantitative measurement of the topology of neurotransmitter
release along developing axons. |
