Fibre type composition of single motor units during synapse elimination in neonatal rat soleus muscle


Skeletal motor neurones innervate the specialized ‘types’ of fibres comprising most mammalian muscles in a characteristic fashion: each motor neurone forms a ‘motor unit’ by innervating a set of fibres all of the same type1–4. Because the type expression of adult muscle fibres is plastic and apparently controlled by their innervation, each motor neurone is thought to impose a common type differentiation on all the fibres in its motor unit4–6. However, the situation in developing muscles cannot be this simple. Muscle fibres in neonates receive synaptic input from several motor neurones and achieve the adult, single innervation only after a period of ‘synapse elimination’7,8. Despite this polyneuronal innervation, differentiated fibre types are present in neonatal muscles9–14. This means either that the motor neurones polyne-uronally innervate fibres in a random fashion and type expression is not determined by innervation or that the polyneuronal innervation is ordered in such a way that each fibre could receive unambiguous instructions for type differentiation. We have investigated these possibilities here by determining the fibre type composition of motor units in neonatal rat soleus muscle. We find that even during the time of poly neuronal innervation each motor neurone confines its innervation to largely one of two fibre types present in the muscle. Therefore, some mechanism during early development segregates the synapses of two groups of soleus motor neurones onto two separate populations of soleus muscle fibres.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Landmesser, L. T. A. Rev. Neurosci. 3, 279–302 (1980).

    CAS  Article  Google Scholar 

  2. 2

    Buchthal, F. & Schmalbruch, H. Physiol. Rev. 60, 90–142 (1980).

    CAS  Article  Google Scholar 

  3. 3

    Burke, R. E. & Edgerton, V. R. in Exercise and Sport Sciences Reviews (eds Wilmore, J. H. & Keogh, J. F.) 31–81 (Academic, New York, 1975).

    Google Scholar 

  4. 4

    Vrbova, G., Gordon, T. & Jones, R. Nerve-Muscle Interaction (Chapman & Hill, London, 1978).

    Google Scholar 

  5. 5

    Pette, D. (ed.) Plasticity of Muscle (Walter de Gruyter, Berlin, 1980).

  6. 6

    Jolesz, F. & Sreter, F. A. A. Rev. Physiol. 43, 531 –552 (1981).

    CAS  Article  Google Scholar 

  7. 7

    Redfern, P. A. J. Physiol, Lond. 209, 701–709 (1970).

    CAS  Article  Google Scholar 

  8. 8

    Brown, M. C., Jansen, J. K. S. & Van Essen, D. J. Physiol., Lond. 261, 387–422 (1976).

    CAS  Article  Google Scholar 

  9. 9

    Riley, D. A. Expl Neurol. 56, 400–409 (1977).

    CAS  Article  Google Scholar 

  10. 10

    Brooke, M. H., Williamson, E. & Kaiser, K. K. Archs Neurol. 25, 360–366 (1971).

    CAS  Article  Google Scholar 

  11. 11

    Rubinstein, N. A. & Kelly, A. M. Devl Biol. 62, 473–485 (1978).

    CAS  Article  Google Scholar 

  12. 12

    Rubinstein, N. A. & Kelly, A. M. J. Cell Biol. 90, 128–144 (1981).

    CAS  Article  Google Scholar 

  13. 13

    Butler-Browne, G. S. & Whalen, R. G. Devl Biol. 102, 324–334 (1984).

    CAS  Article  Google Scholar 

  14. 14

    Rowlerson, A. J. Physiol., Lond. 301, 19P (1980).

  15. 15

    Whalen, R. G. et al. Nature 292, 805–809 (1981).

    ADS  CAS  Article  Google Scholar 

  16. 16

    Gauthier, G. F., Lowey, S., Benfield, P. A. & Hobbs, A. W. J. Cell Biol. 92,471–484 (1982).

    CAS  Article  Google Scholar 

  17. 17

    Fitzsimons, R. B. & Hoh, J. F. Y. J. Neurol. Sci. 52, 367–384 (1981).

    CAS  Article  Google Scholar 

  18. 18

    Edström, L. & Kugelberg, E. J. Neurol. Neurosurg. Psychiat. 31, 424–433 (1968).

    Article  Google Scholar 

  19. 19

    Kugelberg, E. J. neurol. Sci. 27, 269–289 (1976).

    CAS  Article  Google Scholar 

  20. 20

    Burke, R. E., Levine, D. N., Tsairis, P. & Zajac, F. E. J. Physiol., Lond. 234,723–748 (1973).

    CAS  Article  Google Scholar 

  21. 21

    Pearse, A. G. E. Histochemistry, Theoretical and Applied (Little, Brown, Boston, 1968).

    Google Scholar 

  22. 22

    Thompson, W. J. J. Physiol., Lond. 335, 343–352 (1983).

    CAS  Article  Google Scholar 

  23. 23

    Thompson, W. & Jansen, J. K. S. Neuroscience 2, 523–535 (1977).

    CAS  Article  Google Scholar 

  24. 24

    Betz, W. J., Caldwell, J. H. & Ribchester, R. R. J. Physiol., Lond. 297, 463–478 (1979).

    CAS  Article  Google Scholar 

  25. 25

    McLennan, I. S. Devl Biol. 97, 229–238 (1983).

    CAS  Article  Google Scholar 

  26. 26

    Elizalde, A., Huerta, M. & Stefani, E. J. Physiol., Lond. 340, 513–524 (1983).

    CAS  Article  Google Scholar 

  27. 27

    Gambke, B., Lyons, G. E., Haselgrove, J., Kelly, A. M. & Rubinstein, N. A. FEBS Lett. 156, 335–339 (1983).

    CAS  Article  Google Scholar 

  28. 28

    Butler, J., Cosmos, E. & Brierley, J. J. expl. Zool. 224, 65–80 (1982).

    CAS  Article  Google Scholar 

  29. 29

    Vogel, M. W. & Landmesser, L. T. Soc. Neurosci. Abstr. 9, 62 (1983).

    Google Scholar 

  30. 30

    Kugelberg, E., Edström, L. & Abbruzzese, M. J. Neurol. Neurosurg. Psychiat. 33, 319–329 (1970).

    CAS  Article  Google Scholar 

  31. 31

    Gauthier, G. F. & Hobbs, A. W. Expl Neurol. 76, 331–346 (1982).

    CAS  Article  Google Scholar 

  32. 32

    Gordon, H. thesis, Calif. Inst. Tech. (1983).

  33. 33

    Thompson, W. J., Sutton, L. & Riley, D. A. Soc. Neurosci. Abstr. 9, 321(1983).

    Google Scholar 

  34. 34

    Guth, L. & Samaha, F. J. Expl Neurol. 28, 365–367 (1970).

    CAS  Article  Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

Thompson, W., Sutton, L. & Riley, D. Fibre type composition of single motor units during synapse elimination in neonatal rat soleus muscle. Nature 309, 709–711 (1984).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.