Summary
The pattern of innervation on individual iliotibialis muscle fibres from axolotl (Ambystoma mexicanum) has been investigated histologically and elctrophysiologically. These polyneural fibres were found to be innervated on average at five end plate sites. The sites were distributed irregularly along each fibre. Average end plate length was found to be approxiamtely 70 μm. Most end plates were separated by less than 1000 μm; 26% by less than 150 μm; the average separation was 516 μm. Advantage was taken of the dual innervation of the muscle to investigate the separation between synaptic terminals from different axons. Some individual fibres were found to be innervated by axons from two different spinal nerves. End plate sites on dually innervated fibres were located by ACh iontophoresis. 30% of such sites were found to be innervated by more than one axon terminal. The average separation of such sites was found to be 950 μm. Four different axons were found to innervate some individual muscle fibres. It is suggested that the unusual ability of axolotl muscle fibres to accept synaptic terminals from different axons at closely adjacent sites may be a major factor underlying selective reinnervation in this animal.
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Brown, M.C., Jansen, J.K.S., Van Essen, D.: Polyneural innervation of skeletal muscle in newborn rats and its elimination during maturation. J. Physiol. (Lond.) 261, 387–422 (1976)
Cass, D.T. Sutton, T.J., Mark, R.F.: Competition between nerves for functional connexions with axolotl muscle. Nature (Lond.) 243, 201–203 (1973)
Fatt, P., Katz, B.: An analysis of the end plate potential recorded with an intra-cellular electrode. J. Physiol. (Lond.) 115, 320–370 (1951)
Francis, E.T.B.: The anatomy of the salamander. Oxford: Clarendon Press 1934
Frank, E., Jansen, J.K.S., Lømo, T., Westgaard, R.H.: The interaction between foreign and original motor nerves innervating the soleus muscles of rats. J. Physiol. (Lond.) 247, 725–743 (1975)
Gairns, F.W.: A modified gold chloride method for the demonstration of nerve endings. Quart. J. 74, 151–153 (1930)
Grimm, L.M.: An evaluation of myotypic respecification in axolotls. J. exp. Zool. 178, 479–496 (1971)
Hess, A.: The structure of extrafusal muscle fibres in frog and their innervation studied by the cholinesterase technique. Amer. J. Anat. 107, 129–152 (1960)
Lewis, P.R., Shute, C.C.D.: The distribution of cholinesterase in cholinergic neurones demonstrated with the electron microscope J. Cell Sci. 1, 381–390 (1966)
Mark, R.F.: Selective innervation of muscle. Brit. med. Bull. 30, 122–126 (1974)
Mark, R.F., Camperhausen, G. von, Lischinsky, D.J.: Nerve-muscle relations in the salamander: possible relevance to nerve regeneration and muscle specificity. Exp. Neurol. 16, 438–449 (1966)
Slack, J.R.: The innervation of axolotl skeletal muscle fibres. J. Physiol. (Lond.) 256, 128P-129P (1976)
Slack, J.R.: Interaction between foreign and regenerating axons in axolotl muscle. Brain Research (in the press)
Sperry, R.W.: The problem of central nervous reorganisation after nerve regeneration and muscle transposition. Quart. Rev. Biol. 20, 311–369 (1945)
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Vacation student assisted by The Dale Fund of the Physiological Society
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Slack, J.R., Docherty, J.R. The pattern of innervation of a polyneural muscle: Axolotl iliotibialis. Cell Tissue Res. 186, 171–180 (1978). https://doi.org/10.1007/BF00219663
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DOI: https://doi.org/10.1007/BF00219663