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Neurotransmitter release and its facilitation in crayfish

II. Duration of facilitation and removal processes of calcium from the terminal

  • Excitable Tissues and Central Nervous Physiology
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Abstract

Excitatory postsynaptic currents (EPSCs) were recorded extracellularly from synaptic spots on crayfish opener muscles. Facilitation was measured in twin pulses with different intervals. When the extracellular calcium concentration, [Ca]0, was raised from 1.7 to 13.5 mM, the duration of facilitation was increased more steeply than can be explained by the higher entry of Ca. The discrepancy can be accounted for by assuming two saturable Ca removal processes, one being inhibited at high [Ca]0 (e.g. 3.4 mM) was greatly prolonged, while at high [Ca]0 (13.5 mM) no effect was observed. It is concluded that one of the Ca removal processes,R 1, depends on [Na]0 and is inhibited by [Ca]0; probably it is a Cai√Na0 exchange.R 1 is predominant at low [Ca]0 and is largely responsible for the short duration of facilitation there. Other removal processes,R 2, are not affected appreciably by [Ca]0 and [Na]0, and they predominate at high [Ca]0. Approximate values for the kinetic constants ofR 1 andR 2 and the inhibition ofR 1 were estimated.

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Authors and Affiliations

  1. Neurobiology Unit, The Hebrew University, Jerusalem, Israel

    I. Parnas & H. Parnas

  2. Physiologisches Institut der Technischen Universität München, Biedersteiner Strasse 29, D-8000, München 40, Federal Republic of Germany

    J. Dudel

Authors
  1. I. Parnas
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  2. H. Parnas
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  3. J. Dudel
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Supported by the Deutsche Forschungsgemeinschaft and by the USA-Israel Binational Foundation

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Parnas, I., Parnas, H. & Dudel, J. Neurotransmitter release and its facilitation in crayfish. Pflugers Arch. 393, 232–236 (1982). https://doi.org/10.1007/BF00584075

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  • DOI: https://doi.org/10.1007/BF00584075

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