Serendiptic Modulation of Transmitter Release: Extracellular Calcium Inhomogeneity

  • Simona Ginsburg
  • Rami Rahamimoff
Part of the Topics in the Neurosciences book series (TNSC, volume 1)


The amplitude and quantal content of synaptic potentials at the neuromuscular synapse of the frog are extremely sensitive to the calcium concentration in the extracellular solution (Jenkinson, 1957; Dodge & Rahamimoff, 1967). When the calcium concentration in the bathing solution is clamped at a constant level by employing a suitable calcium buffer, the average endplate potential amplitude and quantal content are reduced relative to those measured in a Ringer with a similar yet unbuffered free calcium concentration (Ginsburg & Rahamimoff, 1983). This may indicate that the calcium concentration in the extracellular space is inhomogenous, and that normally, its level in the synaptic cleft is probably higher than in the bulk solution. Possible origins for the calcium inhomogeneity may be extracellular matrix components and calcium transporters situated in the synaptic membranes facing the cleft; changes in their distributions and densities may provide the nerve terminal with energetically economical mechanisms for self-regulating synaptic transmission.


Synaptic Cleft Free Calcium Extracellular Calcium Transmitter Release Motor Nerve Terminal 
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Copyright information

© Martinus Nijhoff Publishing, Boston 1986

Authors and Affiliations

  • Simona Ginsburg
    • 1
    • 2
  • Rami Rahamimoff
    • 1
  1. 1.Department of PhysiologyHebrew University-Hadassah Medical SchoolJerusalemIsrael
  2. 2.Everyman’s UniversityTel AvivIsrael

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