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Pflügers Archiv

, Volume 409, Issue 3, pp 258–264 | Cite as

Anion permeability of motor nerve terminals

  • David A. Saint
  • James G. McLarnon
  • David M. J. Quastel
Excitable Tissues and Central Nervous Physiology

Abstract

Motor nerve terminals in mouse and frog display behavior consistent with an appreciable permeability of the nerve terminal membrane to chloride. In mouse diaphragm, in the presence of 15 mM K+ and 2 mM or 8 mM Ca2+, replacement of Cl by NO 3 , Br or acetate causes a transient increase in the quantal release of acetylcholine, measured as the frequency of spontaneously occurring miniature end plate potentials (FMEPP); a rapid rise in FMEPP is followed by a slow decline, with a half-time of about 4 min, to an equilibration level close to the control level. After equilibration in a solution in which the Cl is replaced by another anion, return to Cl-containing solution causes a transient decrease in FMEPP with a subsequent slow recovery. The data are consistent with transient nerve terminal depolarization or hyperpolarization, reflecting a nerve terminal permeability to anions in the sequence Cl>Br>NO 3 >acetate. In 5 mM K+, changes in nerve terminal excitability, determined using focal stimulation, are also consistent with alteration of nerve terminal membrane potential as a consequence of anion substitution. The time course of relaxation of FMEPP after a change from Cl to an anion of lower permeability, or vice versa, is considerably slower than that expected if Cl permeability of nerve terminals is similar to that of skeletal muscle fibres, and if the nerve terminal behaves as a single compartment. In frog cutaneous pectoris, transient changes in FMEPP produced by substitution of anions in the bathing solution were similar to those produced in mouse diaphragm, but more rapid in time course.

Key words

Nerve terminal Anion permeability Transmitter release 

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References

  1. Aickin CC, Brading AF (1985) Advances in the understanding of transmembrane ionic gradients and permeabilities in smooth muscle obtained by using ion-selective micro-electrodes. Experimentia 41:879–887Google Scholar
  2. Chiu SY, Ritchie JM (1982) Evidence for the presence of potassium channels in the internode of frog myelinated nerve fibres. J Physiol (Lond) 322:485–501Google Scholar
  3. Cohen I, Van der Kloot W (1976) The effects of pH changes on the frequence of miniature end plate potentials at the frog neuromuscular junction. J Physiol (Lond) 262:401–414Google Scholar
  4. Cole WV (1955) Motor ending in the striated muscle of vertebrates. J Comp Neurol 102:671–715Google Scholar
  5. Cooke JD, Quastel DMJ (1973a)Transmitter release by mammalian motor nerve terminals in response to focal polarization. J Physiol (Lond) 228:377–405Google Scholar
  6. Cooke JD, Quastel DMJ (1973b) The specific effect of potassium on transmitter release by motor nerve terminals and its inhibition by calcium. J Physiol (Lond) 228:435–458Google Scholar
  7. Cooke JD, Okamoto K, Quastel DMJ (1973) The role of calcium in depolarization-secretion coupling at the motor nerve terminal. J Physiol (Lond) 228:459–497Google Scholar
  8. Datyner MB, Gage PW (1980) Phasic secretion of acetylcholine at a mammalian neuromuscular junction. J Physiol (Lond) 303:299–314Google Scholar
  9. Del Castillo J, Katz B (1954) Changes in endplate activity produced by presynaptic polarization. J Physiol (Lond) 124:586–604Google Scholar
  10. Dreyer F, Peper K (1974) A monolayer preparation of innervated skeletal muscle fibres of the M. Cutaneus Pectoris of the frog. Pflügers Arch 248:257–262Google Scholar
  11. Furshpan EJ (1956) The effects of osmotic pressure changes on the spontaneous activity at motor nerve endings. J Physiol (Lond) 134:689–697Google Scholar
  12. Gage PW, Quastel DMJ (1966) Competition between sodium and calcium ions in transmitter release at mammalian neuromuscular junctions. J Physiol (Lond) 185:95–123Google Scholar
  13. Hodgkin AL, Horowicz P (1959) The influence of potassium and chloride ions on the membrane potential of single muscle fibers. J Physiol (Lond) 148:127–160Google Scholar
  14. Hutter OF, Padsha SM (1959) Effect of nitrate and other anions on the membrane resistance of frog skeletal muscle. J Physiol (Lond) 146:117–132Google Scholar
  15. Landau EM (1969) The interaction of presynaptic polarization with calcium and magnesium in modifying spontaneous transmitter release from mammalian motor nerve terminals. J Physiol (Lond) 203:281–299Google Scholar
  16. Liley AW (1956) The effects of presynaptic polarization on the spontaneous activity at the mammalian neuromuscular junction. J Physiol (Lond) 134:427–443Google Scholar
  17. Noble D (1966) Application of Hodgkin-Huxley equations to excitable tissues. Physiol Rev 46:3–50Google Scholar
  18. Palade PT, Barchi RL (1977) Characteristics of the chloride conductance in muscle fibers of the rat diphragm. J Gen Physiol 69:325–342Google Scholar
  19. Quastel DMJ, Sastry BR, Steeves JD (1981) Focal excitation of motor nerve terminals. 8th Int Congr Pharmacol (IUPHAR), Abstract, p. 646Google Scholar
  20. Rudel R, Lehmann-Horn F (1985) Membrane changes in cells from myotonia patients. Physiol Rev 65:310–356Google Scholar
  21. Saint DA, Quastel DMJ (1986) Modification of motor nerve terminal excitability by alkanols and volatile anaesthetics. Brit J Pharmacol 88:747–756Google Scholar
  22. Takeuchi A, Takeuchi N (1959) Active phase of frog's end-plate potential. J Neurophysiol 22:395–411Google Scholar
  23. Weast RC (ed) (1969) Handbook of chemistry and physics50th edn., The Chemical Rubber Co.Cleveland, USAGoogle Scholar
  24. Wright EM, Diamond JM (1977) Anion selectivity in biological systems. Physiol Rev 57:109–156Google Scholar

Copyright information

© Springer-Verlag 1987

Authors and Affiliations

  • David A. Saint
    • 1
  • James G. McLarnon
    • 1
  • David M. J. Quastel
    • 1
  1. 1.Department of Pharmacology and Therapeutics, Faculty of MedicineThe University of British ColumbiaVancouverCanada

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