Advertisement

Pflügers Archiv

, Volume 406, Issue 5, pp 449–457 | Cite as

Dependence of double-pulse facilitation on amplitude and duration of the depolarization pulses at frog's motor nerve terminals

  • J. Dudel
Excitable Tissues and Central Nervous Physiology

Abstract

Motor nerve terminals of the frog were depolarized by pairs of pulses with 5 to 10 ms interval and the resulting quantal transmitter releases were determined. In ‘fixed pulse facilitation”,Fc, the second pulse was kept constant, and the effect of a varying pre-pulse was measured, comparing the thus facilitated release after the fixed pulse to control release after the fixed pulse alone. If depolarization in the pre-pulse was increased from threshold to almost saturation level of release,Fc had a maximum,\(\hat F_c \), at about 1/10 the saturation level of release, as reported before. In ‘double-pulse facilitation’,Fd, two identical pulses were applied, and the facilitated release after the second pulse was compared to control release after the first pulse. On increasing pulse duration from 0.4 to 2.5 ms, at fixed depolarization levels,Fd had a peak at short pulse duration and low release, and declined with increasing pulse duration and release. This dependence is expected if facilitation is caused by ‘residual Ca’. Alternatively, if at fixed duration depolarization in the pulses was increased from threshold level, in most preparationsFd rose to a maximum at low depolarization and release, declined to a minimum at the depolarization level of\(\hat F_c \), and rose again for larger depolarizations. In some preparations, and for short pulses, the peak ofFd at low depolarizations was not observed, but alwaysFd increased with depolarization can be explained by the residual Ca theory, if at depolarizations larger than that which produced\(\hat F_c \) and the minimum ofFd, Ca-inflow decreases. The same was concluded before from the decline ofFc with increasing depolarization in this range. While thus forFc andFd, the effects of changes in pulse amplitude and duration on facilitation can be explained by the residual Ca theory, the further increase of release with simultaneous decline of Ca-inflow at large depolarizations indicates that in addition to [Ca]i another potential dependent activator controls release.

Surprisingly, at 0°C no facilitation could be measured in spite of large release. For low pulse amplitudes, release had a large Q10 of 10 to 40 in the range from 0°C to 20°C.

Key words

Release of transmitter quanta Frog's endplate Facilitation Temperature dependance of release 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Barrett EF, Barrett JN, Botz D, Chang DB, Mahaffey D (1978) Temperature-sensitive aspects of evoked and spontaneous transmitter release at the frog neuromuscular junction. J Physiol (Lond) 279:253–273Google Scholar
  2. Bevan S, Grampp W, Miledi R (1976) Properties of spontaneous potentials at denervated motor endplates of the frog. Proc R Soc Lond [Biology] 194:195–210Google Scholar
  3. Del Castillo J, Katz B (1954) Statistical factors involved in neuromuscular facilitation and depression. J Physiol (Lond) 124:574–585Google Scholar
  4. Dodge F, Rahamimoff R (1967) Cooperative action of calcium ions in transmitter release at the neuromuscular junction. J Physiol (Lond) 193:419–432Google Scholar
  5. Dudel J (1983a) Graded or all-or-nothing release of transmitter quanta by local depolarizations of nerve terminals on crayfish muscle? Pflügers Arch 398:155–164Google Scholar
  6. Dudel J (1983b) Transmitter release triggered by a local depolarization in motor nerve terminals of the frog: role of calcium entry and of depolarization. Neurosci Lett 41:133–138Google Scholar
  7. Dudel J (1984a) Control of quantal transmitter release at frog's motor nerve terminals. I. Dependence on amplitude and duration of depolarization. Pflügers Arch 402:225–234Google Scholar
  8. Dudel J (1984b) Control of quantal transmitter release at frog's motor nerve terminals. II. Modulation by de- or hyperpolarizing pulses. Pflügers Arch 402:235–243Google Scholar
  9. Dudel J, Parnas I, Parnas H (1982) Neurotransmitter release and its facilitation in crayfish. III. Amplitude of facilitation and inhibition of entry of calcium into the terminal by magnesium. Pflügers Arch 393:237–242Google 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 399:1–10Google Scholar
  11. Dudel J, Parnas I, Cohen I, Franke Ch (1984) Excitability and depolarization-release characteristics of excitatory nerve terminals in a tail muscle of spiny lobster. Pflügers Arch 401: 293–296Google Scholar
  12. Katz B, Miledi R (1967) The release of acetylcholine from nerve endings by graded electric pulses. Proc R Soc Lond [Biology] 167:23–38Google Scholar
  13. Katz B, Miledi R (1968) The role of calcium in neuromuscular facilitation. J Physiol (Lond) 195:481–492Google Scholar
  14. Llinás R, Steinberg I, Walton K (1981) Relationship between presynaptic calcium current and postsynaptic potential in squid giant synapse. Biophys J 33:323–352Google Scholar
  15. Mallart A (1984) Presynaptic currents in frog motor endings. Pflügers Arch 400:8–13Google Scholar
  16. Matzner H, Parnas H, Parnas I (1986) Characterization of entry and removal of calcium and release of neurotransmitter at the frog neuromuscular junction. (in preparation)Google Scholar
  17. Molgó J, Thesleff S (1982) Electrotonic properties of motor nerve terminals. Acta Physiol Scand 114:271–275Google Scholar
  18. Mullins L (1981) Ion transport in heart Raven Press, New YorkGoogle Scholar
  19. Parnas H, Segel L (1980) A theoretical explanation for some effects of calcium on the facilitation of neurotransmitter release. J Theor Biol 84:3–29Google Scholar
  20. Parnas H, Segel L (1981) A theoretical study of calcium entry in nerve terminals, with application to neurotransmitter release. J Theor Biol 91:125–169Google Scholar
  21. Parnas H, Dudel J, Parnas I (1982) Neurotransmitter release and its facilitation in crayfish. I. Saturation kinetics of release, and of entry and removal of calcium. Pflügers Arch 393:1–14Google Scholar
  22. Parnas H, Dudel J, Parnas I (1986) Neurotransmitter release and its facilitation in crayfish. VII. Another voltage dependent process beside Ca entry controls the time course of phasic release. Pflügers Arch 406:121–130Google Scholar
  23. Parnas I, Parnas H, Dudel J (1982a) Neurotransmitter release and its facilitation in crayfish. II. Duration of facilitation and removal processes of calcium from the terminal. Pflügers Arch 393:232–236Google Scholar
  24. Parnas I, Parnas H, Dudel J (1982b) Neurotransmitter release and its facilitation in crayfish. V. Basis for synapse differentiation of the fast and slow type in one axon. Pflügers Arch 395:261–270Google Scholar
  25. Parnas I, Dudel J, Parnas H (1984) Depolarization dependence of the kinetics of phasic transmitter release at the crayfish neuromuscular junction. Neurosci Lett 50:157–162Google Scholar
  26. Parnas I, Parnas H, Dudel J (1986) Neurotransmitter release and its facilitation in crayfish. VIII. Modulation of release by hyperpolarizing pulses. Pflügers Arch 406:131–137Google Scholar
  27. Rahamimoff R (1968) A dual effect of calcium ions on neuromuscular facilitation. J Physiol (Lond) 195:471–480Google Scholar
  28. Schaefer H, Haass P (1939) Über einen lokalen Erregungsstrom an der motorischen Endplatte. Pflügers Arch 242:364–381Google Scholar
  29. Smith SJ, Augustine GJ, Charlton MP (1985) Transmission at voltage-clamped giant synapse of the squid: Evidence for cooperativity of presynaptic calcium action. Proc Natl Acad Sci USA 82:622–625Google Scholar
  30. Stockbridge N, Moore JW (1984) Dynamics of intracellular calcium and its possible relationship to phasic transmitter release and facilitation at the frog neuromuscular junction. J Neurosci, 4:803–811Google Scholar
  31. Wojtowicz JM, Atwood HL (1983) Maintained depolarization of synaptic terminals facilitates nerve-evoked transmitter release at a crayfish neuromuscular junction. J Neurobiol 14:385–390Google Scholar
  32. Zucker RS, Stockbridge N (1983) Presynaptic calcium diffusion and the time courses of transmitter release and synaptic facilitation at the squid giant synapse. J Neurosci 3:1263–1269Google Scholar

Copyright information

© Springer-Verlag 1986

Authors and Affiliations

  • J. Dudel
    • 1
  1. 1.Physiologisches Institut der Technischen Universität MünchenMünchen 40Federal Republic of Germany

Personalised recommendations