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Invertebrate Neuroscience

, Volume 3, Issue 2–3, pp 81–87 | Cite as

Strength of synaptic transmission at neuromuscular junction of crustaceans and insects in relation to calcium entry

  • H. L. AtwoodEmail author
  • S. Karunanithi
  • J. Georgiou
  • M. P. Charlton
Articles from the ICINN 97 Conference Synaptic Transmission and Plasticity

Abstract

Crustacean and insect neuromuscular junctions typically include numerous small synapses, each of which usually contains one or more active zones, which possess voltage-sensitive calcium channels and are specialized for release of synaptic vesicles. Strength of transmission (the number of quantal units released per synapse by a nerve impulse) varies greatly among different endings of individual neurons, and from one neuron to another. Ultrastructural features of synapses account for some of the physiological differences at endings of individual neurons. The nerve terminals that release more neurotransmitter per impulse have a higher incidence of synapses with more than one active zone, and this is correlated with more calcium build-up during stimulation. However, comparison of synaptic structure in neurons with different physiological phenotypes indicates no major differences in structure that could account for their different levels of neurotransmitter release per impulse, and release per synapse differs among neurons despite similar calcium build-up in their terminals during stimulation. The evidence indicates differences in calcium sensitivity of the release process among neurons as an aspect of physiological specialization.

Key words

neuromuscular crustacean Drosophila synapse quantal release calcium 

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Copyright information

© Sheffield Academic Press 1997

Authors and Affiliations

  • H. L. Atwood
    • 1
    Email author
  • S. Karunanithi
    • 1
  • J. Georgiou
    • 1
  • M. P. Charlton
    • 1
  1. 1.Department of PhysiologyUniversity of TorontoTorontoCanada

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