Advertisement

Pflügers Archiv

, Volume 401, Issue 4, pp 408–413 | Cite as

The voltage and temperature dependence of the end-plate current in frog skeletal muscle

  • M. Kordaš
  • R. Zorec
Excitable Tissues and Central Nervous

Abstract

The effect of membrane potential (V) on the half-time (t1/2) of the falling phase of the end-plate current (e.p.c.) was found to obey the equationt1/2=A·eBV+C, whereA,B andC are constants.

The temperature dependence oft1/2 was found to follow the Arrhenius equation. The activation energy (Ea) varied from about 50 kJ/mol to about 120 kJ/mol.

At membrane potentials between about −40 mV and −140 mV, theEa/V relation was similar in all end-plates investigated:Ea increased if membrane potential was made more negative. At membrane potentials between about +60 mV and −40mV, however, theEa/V relation was different in different end-plates: If membrane potential was made more negative,Ea was either increased, or not affected, or decreased.

It is concluded that at negative levels of membrane potential the decay of the e.p.c. depends on average life-time of ionic channels, opened up by the action of acetylcholine on junctional receptors. At strongly positive levels of membrane potential, however, the decay of the e.p.c. can be determined by the average life-time of ionic channels or by the clearance of transmitter from the synaptic cleft, or both. Either of these processes can be reflected in the value of constant C in the above equation.

Key words

Neuromuscular junction End-plate current Acetylcholine receptor 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Albuquerque EX, Oliveira AC (1979) Physiological studies on the ionic channel of nicotinic neuromuscular synapses. In: Ceccarelli B, Clement F (eds) Advances in cytopharmacology. Raven Press, New York, p 197–211Google Scholar
  2. Anderson CR, Stevens CF (1973) Voltage clamp analysis of acetylcholine produced end-plate current fluctuations at frog neuromuscular junction. J Physiol 235:655–691Google Scholar
  3. Ashford MLJ, Macdonald AG, Wann KT (1982) The effects of hydrostatic pressure on the spontaneous release of transmitter at the frog neuromuscular junction. J Physiol 333:531–543Google Scholar
  4. Colquhoun D (1979) The link between drug binding and response: Theories and observations. In: O'Brien RD (ed) The receptors. A comprehensive treatise. Plenum Press, New York, London, pp 93–142Google Scholar
  5. Colquhoun D (1981) How fast do drugs work? TIPS 2:212–217Google Scholar
  6. Colquhoun D, Dreyer F, Sheridan RE (1979) The actions of tubocurarine at the frog neuromuscular junction. J Physiol 293:247–284Google Scholar
  7. Cull-Candy SG, Miledi R, Trautmann A (1979) End-plate currents and acetylcholine noise at normal and myasthenic human end-plates. J Physiol 287:247–265Google Scholar
  8. Gage PW (1976) Generation of end-plate potentials. Physiol Rev 56:177–247Google Scholar
  9. Gage PW, McBurney RN (1975) Effects of membrane potential, temperature and neostigmine on the conductance change, caused by a quantum of acetylcholine at the toad neuromuscular junction. J Physiol 244:385–407Google Scholar
  10. Howell JN, Jenden DJ (1967) T-tubules of skeletal muscle: Morphological alteration which interrupt excitation-contraction coupling. Fed Proc 26:553Google Scholar
  11. Humar M, Kordaš M, Melik Ž (1980) The effect of papaine on the time course of the end-plate current. Pflügers Arch 386:67–70Google Scholar
  12. Katz B, Miledi R (1973) The binding of acetylcholine to receptors and its removal from the synaptic cleft. J Physiol 231:549–547Google Scholar
  13. Katz B, Miledi R (1978) A re-examination of curare action at the motor end-plate. Proc R Soc Lond B 203:119–133Google Scholar
  14. Kordaš M (1969) The effect of membrane polarization on the time course of the end-plate current in frog sartorius muscle. J Physiol 204:493–502Google Scholar
  15. Kordaš M (1972a) An attempt at an analysis of the factors determining the time course of the end-plate current. I. The effects of prostigmine and of the ratio of Mg2+ to Ca2+. J Physiol 224:317–332Google Scholar
  16. Kordaš M (1972b) An attempt at an analysis of the factors determining the time course of the end-plate current. II. Temperature. J Physiol 224:333–348Google Scholar
  17. Kordaš M (1977a) On the role of junctional cholinesterase in determining the time course of the end-plate current. J Physiol 270:133–150Google Scholar
  18. Kordaš M (1977b) The effect of atropine on neuromscular transmission. Iugosl Physiol Pharmacol Acta 13:295–300Google Scholar
  19. Kordaš M (1982) An analysis of factors which determine the “voltage sensitivity” of the end-plate current. Gen Physiol Biophys 1:189–197Google Scholar
  20. Kordaš M, Brzin M, Majcen Ž (1975) A comparison of the effect of cholinesterase inhibitors on end-plate current and on cholinesterase activity in frog muscle. Neuropharmacology 14:971–800Google Scholar
  21. Kuffler SW, Doju Yoshikami (1975) The distribution of acetylcholine sensitivity at the postsynaptic membrane of vertebrate twitch muscles: Iontophoretic mapping in the micron range. J Physiol 244:703–730Google Scholar
  22. Magleby KL, Stevens CF (1972a) The effect of voltage on the time course of end-plate currents. J Physiol 223:141–171Google Scholar
  23. Magleby KL, Stevens CF (1972b) A quantitative description of end-plate currents. J Physiol 223:173–197Google Scholar
  24. Peper K, Bradley RJ, Dreyer F (1982) The acetylcholine receptor at the neuromuscular junction. Physiol Rev 62:1271–1340Google Scholar
  25. Sakmann B, Adams PR (1979) Biophysical aspects of agonist action at frog end-plate. In: Jacobs J (ed) Advances in pharmacology and therapeutics. Pergamon Press, Oxford, pp 81–90Google Scholar
  26. Sakmann B, Patlak J, Neher E (1980) Single acetylcholine-activated channels show burst kinetics of desensitizing concentrations of agonist. Nature 286:71–73Google Scholar
  27. Scuka M (1975) The amplitude and time course of the end-plate current at various pH levels in frog sartorius muscle. J Physiol 249:183–195Google Scholar
  28. Sket B (1967) Dvoživke. In: Bavdaž M, Bole J, Brelih S, Sket B (eds) Ključi za določevanje živali. Inštitut za biologijo Univerze v Ljubljani, Društvo biologov Slovenije, Ljubljana, pp 1–25Google Scholar
  29. Snetkov VA (1977) Vlijanie fenilalkilaminov na potencialozavisimost toka koncevoi plastinki myšečnogo volokna ljaguški. Dokl Akad Nauk SSSR 234:947–950Google Scholar
  30. Steinbach JH, Stevens CF (1976) Neuromuscular transmission, In: Llinas R, Precht W (eds) Frog neurobiology. Springer, Berlin, Heidelberg, New York, pp 33–77Google Scholar
  31. Stevens CF (1978) Interactions between intrinsic membrane protein and electric field. An approach to study nerve excitability. Biophys J 22:295–306Google Scholar
  32. Takeuchi A, Takeuchi N (1959) Active phase of frog's end-plate potential. J Neurophysiol 22:395–411Google Scholar

Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • M. Kordaš
    • 1
  • R. Zorec
    • 1
  1. 1.Institute of Pathophysiology, Medical FacultyUniversity of Edvard KardeljLjubljanaYugoslavia

Personalised recommendations