Pflügers Archiv

, Volume 401, Issue 3, pp 293–296 | Cite as

Excitability and depolarization-release characteristics of excitatory nerve terminals in a tail muscle of spiny lobster

  • J. Dudel
  • I. Parnas
  • I. Cohen
  • Ch. Franke
Excitable Tissues and Central Nervous Physiology

Abstract

In the deep abdominal L1-extensor muscle of the spiny lobster (Panulirus penicillatus) quantal excitatory postsynaptic currents (EPSCs) were recorded through macropatch-clamp electrodes. Release of transmitter quanta from terminals was also elicited by depolarizing current pulses given through the recording electrode. The majoritiy of terminals were excitable: on increasing the depolarization pulses, release was triggered at a threshold in an all-ornothing manner. If excitation was blocked by tetrodotoxin (TTX), release was graded with depolarization reaching the amplitude of the all-or-nothing response at pulse amplitudes several times higher than the former threshold level. Some inexcitable terminals were also found: in these, release was graded for increasing depolarization pulses, and TTX did not alter the depolarization-release relation. Among the other types of terminals studied with the same technique, the proportion of excitable terminals in this lobster tail muscle is higher than in the crayfish opener and lower than in the frog's cutaneous pectoris muscle.

The contribution of the increase in intraterminal Ca concentration to the control of release was estimated using facilitation of a test EPSC as an indicator of Ca inflow during a preceding depolarization pulse. This facilitation was found to have a maximum at a certain pulse amplitude,\(p_{\hat F}\), and to decline for larger depolarizations. Release, however, rose considerably for depolarizations larger than those effected at\(p_{\hat F}\).It is concluded that, like in crayfish and frog motor terminals, release is controlled directly by depolarization in addition to the control by Ca-inflow.

Key words

Synaptic transmitter release Nerve terminals Excitability Depolarization-release relation 

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References

  1. Braun M, Schmidt RF (1966) Potential changes recorded from the frog motor nerve terminal during its activation. Pflügers Arch 287:56–80CrossRefGoogle Scholar
  2. Brigant JL, Mallart A (1962) Presynaptic currents in mouse motor endings. J Physiol (Lond) 333:619–636Google Scholar
  3. Castillo A del, Katz B (1954) Quantal components of the endplate potential. J Physiol (Lond) 124:560–573Google Scholar
  4. Dudel J (1965) The mechanism of presynaptic inhibition at the crayfish neuromuscular junction. Pflügers Arch 284:66–80CrossRefGoogle Scholar
  5. Dudel J (1981) The effect of reduced calcium on quantal unit current and release at the crayfish neuromuscular junction. Pflügers Arch 391:35–40PubMedCrossRefGoogle Scholar
  6. Dudel J (1982) Transmitter release by graded local depolarization of presynaptic nerve terminals at the crayfish neuromuscular junction. Neurosci Lett 32:181–186PubMedCrossRefGoogle Scholar
  7. Dudel J (1983a) Graded or all-or-nothing release of transmitter quanta by local depolarizations of nerve terminals on crayfish muscle? Pflügers Arch 398:155–164PubMedCrossRefGoogle Scholar
  8. Dudel J (1983b) Release triggered by a local depolarization in motor nerve terminals of the frog: Role of Ca entry and of depolarization. Neurosci Lett 41:133–138PubMedCrossRefGoogle Scholar
  9. Dudel J, Kuffler SW (1961) Presynaptic inhibition at the crayfish neuromuscular junction. J Physiol (Lond) 155:543–562Google Scholar
  10. Dudel J, Parnas I, Parnas H (1983) Neurotransmitter release and its facilitation in crayfish muscle. VI. Release determined by both, intracellular calcium concentration and depolarization of the nerve terminal. Pflügers Arch 399:1–10PubMedCrossRefGoogle Scholar
  11. Henĉek M, Zachar J (1977) Calcium currents and conductances in the muscle membrane of the crayfish. J Physiol (Lond) 268:51–71Google Scholar
  12. Johnson EW, Wernig A (1971) The binomial nature of transmitter release at the crayfish neuromuscular junction. J Physiol (Lond) 218:757–767Google Scholar
  13. Katz B, Miledi R (1965) The effects of calcium on acetylcholine release from motor nerve terminals. Proc R Soc Lond [Biol] 167:496–503Google Scholar
  14. Katz B, Miledi R (1967) The release of acetylcholine from nerve endings by graded electric pulses. Proc R Soc Lond [Biol] 161:23–38CrossRefGoogle Scholar
  15. Katz B, Miledi R (1968) The role of calcium in neuromuscular facilitation. J Physiol (Lond) 195:481–492Google Scholar
  16. Llinás R, Steinberg IZ, Walton K (1981) Relationship between presynaptic calcium current and postsynaptic potential in squid giant synapse. Biophys J 33:323–352PubMedCrossRefGoogle Scholar
  17. Niwa A, Kawai N (1982) Tetrodotoxin-resistant propagating action potentials in presynaptic axon of the lobster. J Neurophysiol 47:353–361PubMedGoogle Scholar
  18. Parnas H, Dudel J, Parnas I (1982a) Neurotransmitter release and its facilitation in crayfish. I. Staturation kinetics of release, and of entry and removal of calcium. Pflügers Arch 393:1–14PubMedCrossRefGoogle Scholar
  19. Parnas H, Dudel J, Parnas I (1984a)Google Scholar
  20. Parnas I, Atwood HL (1966) Phasic and tonic neuromuscular systems in the abdominal extensor muscles of the crayfish and rock lobster. Comp Biochem Physiol (Lond) 18:701–723CrossRefGoogle Scholar
  21. Parnas I, Parnas H, Dudel J (1982b) Neurotransmitter release and its facilitation in crayfish muscle. V. Basis for synapse differentiation of the fast and slow type in one axon. Pflügers Arch 395:261–270PubMedCrossRefGoogle Scholar
  22. Parnas I, Dudel J, Cohen I, Franke Ch (1984b) Strengthening of synaptic contacts of one axon on elimination of an agonistic second axon. J Neurobiol (in press)Google Scholar
  23. Takeuchi A, Takeuchi N (1966) A study of the inhibitory action of γ-aminobutyric acid on neuromuscular transmittion in the crayfish. J Physiol (Lond) 183:418–432Google Scholar
  24. Wojtowicz JM, Atwood HL (1983) Maintained depolarization of synaptic terminals facilitates nerve-evoked transmitter release at a crayfish neuromuscular junction. J Neurobiol 14:385–390PubMedCrossRefGoogle Scholar
  25. Zucker RS (1974) Crayfish neuromuscular facilitation activated by constant presynaptic action potentials and depolarizing pulses. J Physiol (Lond) 241:69–89Google Scholar

Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • J. Dudel
    • 1
  • I. Parnas
    • 2
  • I. Cohen
    • 2
  • Ch. Franke
    • 1
  1. 1.Physiologisches Institut der Technischen Universität MünchenMünchen 40Germany
  2. 2.Department of NeurobiologyHebrew UniversityJerusalemIsrael

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