The Journal of Neuroscience, November 1, 2000, 20(21):8077-8086
Transmitter-Receptor Interactions between Growth Cones of
Identified Lymnaea Neurons Determine Target Cell
Selection In Vitro
Gaynor E.
Spencer,
Ken
Lukowiak, and
Naweed I.
Syed
Neuroscience Research Group, Departments of Anatomy and Cell
Biology, Physiology and Biophysics, Health Sciences Centre, Calgary,
Alberta, Canada T2N 4N1
In addition to their involvement in transsynaptic
communication in the adult nervous system, neurotransmitters also
participate in many developmental events, such as neurite initiation
and outgrowth. Although growth cones can release transmitters and are
themselves sensitive to exogenously applied neurotransmitters, a direct
causal relationship between the release of transmitter from one growth cone and its effect on another has not yet been demonstrated. In this
study, we provide evidence that dopamine release from the growth cones
of an identified Lymnaea neuron, right pedal dorsal 1 (RPeD1), differentially regulates the growth cone behavior of its
in vivo target and nontarget neurons in
vitro. In coculture, RPeD1 growth cones enhanced the rate of
growth cone advance from target cells and synaptic connections
developed immediately after contact. In contrast, RPeD1 growth cones
not only inhibited the rate of growth cone advance from nontarget cells
but they also induced growth cone collapse. Using a "sniffer cell"
approach, we demonstrated that both RPeD1 growth cones and somata
released dopamine, which can be detected at a distance of several
hundred micrometers. RPeD1 somata were used to demonstrate that
spontaneous release of dopamine also acted as a chemoattractant for
target growth cones but as a chemorepellent for nontarget growth cones. These effects were mimicked by exogenous dopamine application, and both
RPeD1 growth cone and soma-induced effects were also blocked in the
presence of dopamine receptor antagonists. This study emphasizes the
importance of transmitter-receptor interactions between growth cones
in target cell selection.
Key words:
transmitter; dopamine; growth cone; culture; target
selection; regeneration; neurite outgrowth; mollusc
Copyright © 2000 Society for Neuroscience 0270-6474/00/20218077-10$05.00/0
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