Pflügers Archiv

, Volume 381, Issue 3, pp 209–216 | Cite as

Activity-dependent changes in conduction velocity in the olfactory nerve of the tortoise

  • T. V. P. Bliss
  • M. E. Rosenberg
Excitable Tissues and Central Nervous Physiology


  1. 1.

    The conduction velocity of the compound action potential in the olfactory nerve of the tortoise is affected by previous activity in two ways. First, there is an inverse relation between conduction velocity and the level of activity as determined by the rate of stimulation. Second, in the active, though not in the resting nerve, the action potential initiated by the second of a pair of shocks is conducted faster than that initiated by the first. The period of supernormal conduction velocity set up in the wake of the first response lasts for about 1 s, and at the peak of the effect conduction velocity is increased by up to 27%.

  2. 2.

    Aspects of these phenomena were investigated in vitro. The magnitude of supernormality was diminished by ouabain, and by the substitution of lithium for sodium in the bathing medium; it was enhanced when chloride was replaced by sulphate.

  3. 3.

    Supernormality could not be potentiated by increasing the number of conditioning volleys. The conduction velocity achieved at the peak of the supernormal period was usually as great as, but never greater than the conduction velocity of the resting nerve.

  4. 4.

    These results, together with the results of computations based on the Hodgkin-Huxley equations, suggest that the dependence of conduction velocity on the rate of stimulation is a reflection of a corresponding dependence of intracellular sodium levels on activity. Two classes of explanation for supernormality are considered, one based on the activation of an electrogenic pump, and the other on a transient increase in sodium conductance. The available evidence is insufficient to distinguish between these two hypotheses.


Key words

Nerve conduction Olfactory nerve Tortoise 


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  1. Baldissera, F., Gustafsson, B.: Afterhyperpolarization conductance time course in lumbar motoneurones of the cat. Acta Physiol. Scand.91, 512–527 (1974)Google Scholar
  2. Bliss, T. V. P.: A theoretical investigation of supernormal conduction velocity in unmyelinated nerve. B. Sc. Thesis pp. 40, Dept. of Mathematics, Hatfield Polytechnic (1975)Google Scholar
  3. Bliss, T. V. P., Rosenberg, M. E.: Supernormal conduction velocity in the olfactory nerve of the tortoise. J. Physiol. (Lond.)239, 60–61P (1974)Google Scholar
  4. Brinley, F. J., Mullins, L. J.: Sodium fluxes in internally dialyzed squid axons. J. Gen. Physiol.52, 181–211 (1968)Google Scholar
  5. Bullock, T. H.: Facilitation of conduction rate in nerve fibres. J. Physiol. (Lond.)114, 89–97 (1951)Google Scholar
  6. Chung, S. H., Bliss, T. V. P., Keating, M. J.: The synaptic organization of optic afferents in the amphibian tectum. Proc. R. Soc. Biol. (Lond.)187, 421–447 (1974)Google Scholar
  7. Colquhoun, D., Ritchie, J. M.: The interaction at equilibrium between tetrodotoxin and mammalian non-myelinated nerve fibres. J. Physiol. (Lond.)221, 533–553 (1972)Google Scholar
  8. Donati, F., Kunov, H.: A model for studying velocity variations in unmylinated axons. IEEE Trans. Biomed. Eng.23, 23–28 (1976)Google Scholar
  9. Easton, D. M.: Garfish olfactory nerve: easily accessible source of numerous long, homogenous, non-myelinated axons. Science172, 952–955 (1971)Google Scholar
  10. Gardner-Medwin, A. R.: An extreme supernormal period in cerebellar parallel fibres. J. Physiol. (Lond.)222, 357–371 (1972a)Google Scholar
  11. Gardner-Medwin, A. R.: Supernormality of cerebellar parallel fibres: the effects of changes in potassium concentration in vitro. Acta Physiol. Scand.84, 38–39A (1972b)Google Scholar
  12. Gardner-Medwin, A. R.: The relation between supernormal conduction velocity of cerebellar parallel fibres and the number of conditioning volleys. J. Physiol. (Lond.)232, 22P (1973)Google Scholar
  13. Gasser, H. S.: Olfactory nerve fibers. J. Gen. Physiol.39 473–496 (1956)Google Scholar
  14. George, S. A.: Changes in interspike interval during propagation: quantitative description. Biol. Cybern.26, 209–213 (1977)Google Scholar
  15. George, S. A., Silberstein, P. T.: Conduction velocity after effects of spike activity: quantitative studies. Soc. Neurosci., Abstr3, 217 (1977)Google Scholar
  16. Hill, D. K.: The volume change resulting from stimulation of a giant nerve fibre. J. Physiol. (Lond.)111, 304–327 (1950)Google Scholar
  17. Hodgkin, A. L.: A note on conduction velocity. J. Physiol. (Lond.)125, 221–224 (1954)Google Scholar
  18. Hodgkin, A. L., Huxley, A. F.: A quantitative description of membrane current and its application to conduction and excitation in nerve. J. Physiol. (Lond.)117, 500–544 (1952)Google Scholar
  19. Hodgkin, A. L., Keynes, R. D.: Experiments on the injection of substances into squid giant axon by means of a micro-syringe. J. Physiol. (Lond.)131, 592–616 (1956)Google Scholar
  20. Huxley, A. F.: Ion movements during nerve activity. Ann. N. Y. Acad. Sci.81, 221–246 (1959)Google Scholar
  21. Jack, J. J. B.: Physiology of peripheral nerve fibres in relation to their size. Br. J. Anaesth.47, 173–182 (1975)Google Scholar
  22. Katz, B.: Nerve, muscle and synapse, p. 193. London: McGraw-Hill 1966Google Scholar
  23. Keynes, R. D., Ritchie, J. M.: The movements of labelled ions in mammalian non-myelinated nerve fibres. J. Physiol. (Lond.)179, 333–367 (1965)Google Scholar
  24. Keynes, R. D., Swan, R. C.: The effect of external sodium concentration on the sodium fluxes in frog skeletal muscle. J. Physiol. (Lond.)147, 591–625 (1959)Google Scholar
  25. Landowne, D., Ritchie, J. M.: The binding of tritiated ouabain to mammalian non-myelinated nerve fibres. J. Physiol. (Lond.)207, 529–537 (1970)Google Scholar
  26. Mathews, D. F.: Response patterns of single neurons in the tortoise olfactory epithelium and olfactory bulb. J. Gen. Physiol.60, 166–180 (1972)Google Scholar
  27. Pickens, P. E.: Changes in conduction velocity within a nerve net. J. Neurol.5, 413–420 (1974)Google Scholar
  28. Rang, H. P., Ritchie, J. M.: On the electrogenic sodium pump in mammalian non-myelinated nerve fibres and its activation by various external cations. J. Physiol. (Lond.)196, 183–221 (1968)Google Scholar
  29. Ritchie, J. M., Straub, R. W.: The movement of potassium ions during electrical activity, and the kinetics of the recovery process, in the non-myelinated fibres of the garfish olfactory nerve. J. Physiol. (Lond.)249, 327–348 (1975)Google Scholar
  30. Rosenberg, M. E.: The distribution of the sensory input in the dorsal spinal cord of the tortoise. J. Comp. Neurol.156, 29–38 (1974)Google Scholar
  31. Stein, R. B., Pearson, K. G.: Predicted amplitude and form of action potentials recorded from umyelinated nerve fibres. J. Theor. Biol.32, 539–558 (1971)Google Scholar
  32. Swadlow, H. A.: Systematic variations in the conduction velocity of slowly conducting axons in the rabbit corpus callosum. Exp. Neurol.43, 445–451 (1974)Google Scholar
  33. Waxman, S. G., Swadlow, H. A.: Morphology and physiology of visual callosal axons-evidence for a supernormal period in central myelinated axons. Brain Res.113, 179–187 (1976)Google Scholar

Copyright information

© Springer-Verlag 1979

Authors and Affiliations

  • T. V. P. Bliss
    • 1
  • M. E. Rosenberg
    • 1
  1. 1.National Institute for Medical ResearchLondonUK

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