Noradrenaline synchronizes evoked quantal release at frog neuromuscular junctions

Authors

  • Ella A. Bukcharaeva,

    1. Kazan State Medical University, Academy of Sciences, Kazan, Russian Federation
    2. Kazan Institute of Biology, Academy of Sciences, Kazan, Russian Federation
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  • Kira C. Kim,

    1. Kazan Institute of Biology, Academy of Sciences, Kazan, Russian Federation
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  • J. Moravec,

    1. Department of Animal Physiology and Developmental Biology, Faculty of Sciences, Charles University, Prague 2, Czech Republic
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  • E. E. Nikolsky,

    1. Kazan State Medical University, Academy of Sciences, Kazan, Russian Federation
    2. Kazan Institute of Biology, Academy of Sciences, Kazan, Russian Federation
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  • F. Vyskočil

    Corresponding author
    1. Department of Animal Physiology and Developmental Biology, Faculty of Sciences, Charles University, Prague 2, Czech Republic
    2. Institute of Physiology, Academy of Sciences of the Czech Republic, Prague 4, Czech Republic
    • Corresponding author
      F. Vyskocil: Institute of Physiology, Academy of Sciences of the Czech Republic, Vídenská 1083, Prague 4, Czech Republic. Email: vyskocil@biomed.cas.cz

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Abstract

  • 1Noradrenaline (NA) increases synaptic efficacy at the frog neuromuscular junction. To test the hypothesis that one of the actions of NA is to shorten the period over which evoked quanta are released, we measured the latencies of focally recorded uniquantal endplate currents (EPCs).
  • 2NA shortened the release period for evoked quantal release. The interval between the time when responses with minimal delay appeared and the point at which 90 % of all latencies had occurred was shortened in the presence of 1 × 10−5 M NA by about 35 % at 20 °C and by about 45 % at 8 °C. Inhibitor and agonist experiments showed that NA acts on a β-adrenoreceptor.
  • 3The better synchronization of release significantly increased the size of reconstructed multi- quantal EPCs. This suggests that NA facilitates synaptic transmission by making the release of quanta more synchronous.
  • 4The synchronizing action of NA might potentiate neuromuscular transmission during nerve regeneration, transmitter exhaustion and other extreme physiological states where the quantal content is reduced, such as survival in cold and hibernation.

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