Pflügers Archiv

, Volume 431, Issue 3, pp 325–334 | Cite as

On the possible origin of “giant or slow-rising” miniature end-plate potentials at the neuromuscular junction

  • L. C. Sellin
  • J. Molgó
  • K. Törnquist
  • B. Hansson
  • S. Thesleff
Original Article


Giant or slow-rising miniature end-plate potentials (GMEPPs) caused by vesicular release of acetylcholine (ACh) occur at any time in about 50% of mouse diaphragm neuro muscular junctions, but generally at frequencies less than 0.03 s−1. Their frequency is, unlike that of miniature end-plate potentials (MEPPs), not affected by nerve terminal depolarization. Unlike MEPPs and stimulus-evoked end-plate potentials, GMEPPs have a prolonged time-to-peak and show an increase in time-to-peak with amplitude. By using these differences in amplitude and time course, GMEPPs can be separated from MEPPs. In contrast to MEPPs, GMEPPs are not blocked by botulinum neurotoxin type A. GMEPPs have a greater temperature sensitivity than MEPPs, disappearing at temperatures below 15°C. Long-term paralysis by botulinum toxin and certain drugs which inhibit protein kinase C or affect actin filament polymerization (cytochalasins) enhance the frequency of GMEPPs. End-plate current recordings show that similar postsynaptic ACh receptors are activated by MEPPs and GMEPPs. It is suggested that GMEPPs are not caused by mechanisms involved in “regulated” neurotransmitter release but are generated by “constitutive secretion”.

Key words

Neurotransmitter release Constitutive secretion Miniature end-plate potentials Giant miniature end-plate potentials Protein kinase C 


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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • L. C. Sellin
    • 1
  • J. Molgó
    • 2
  • K. Törnquist
    • 3
  • B. Hansson
    • 4
  • S. Thesleff
    • 4
  1. 1.Division of Biophysics, Department of Physical SciencesUniversity of OuluOuluFinland
  2. 2.Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRSGif sur Yvette cedexFrance
  3. 3.Department of Biosciences, Division of Animal PhysiologyUniversity of Helsinki and the Minerva Foundation Institute for Medical ResearchHelsinkiFinland
  4. 4.Department of PharmacologyUniversity of LundLundSweden

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