AJP - Cell Physiology, Vol 258, Issue 1 C62-C70, Copyright © 1990 by American Physiological Society

ARTICLES

Relative efficacy of slow and fast alpha-motoneurons to reinnervate mouse soleus muscle

G. Desypris and D. J. Parry
Department of Physiology, School of Medicine, University of Ottawa, Ontario, Canada.

Contractile and histochemical properties of reinnervated motor units in soleus muscles of C57BL/6J mice were examined 1 mo after sectioning the soleus nerve. Fifty-one motor units were isolated by the technique of ventral root splitting. Their sizes ranged from 0.4 to 13.6% of whole muscle tetanic tension (Po) with a mean size of 5.3% Po corresponding to 19 motor units. In control unoperated mice, the range was 2.2-8.6% Po, with a mean size of 4.8% Po corresponding to 22 motor units. Although no clear relationship between unit time to peak tension and size was seen in control units, it appeared that in the reinnervated muscle the large units were also slow contracting, whereas the smaller units were predominantly fast contracting. Adenosinetriphosphatase (ATPase) staining revealed an increase in the proportion of muscle area occupied by type I fibers in reinnervated soleus compared with control soleus. Immunohistochemical staining of reinnervated soleus with monoclonal antibodies against type I and IIa myosin showed the presence of hybrid fibers containing both myosins. It is concluded that during reinnervation most motoneurons reinnervate the soleus muscle of the mouse. The hypothesis that slow motoneurons are more adept at expanding their innervating field than fast motoneurons is also supported by the data.

This article has been cited by other articles:

				T. Marqueste, J.-R. Alliez, O. Alluin, Y. Jammes, and P. Decherchi Neuromuscular rehabilitation by treadmill running or electrical stimulation after peripheral nerve injury and repair J Appl Physiol, May 1, 2004; 96(5): 1988 - 1995. [Abstract] [Full Text] [PDF]

				T. J. Marcell Review Article: Sarcopenia: Causes, Consequences, and Preventions J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2003; 58(10): M911 - 916. [Abstract] [Full Text] [PDF]

				E. Barton and C. Morris Review Article: Mechanisms and Strategies to Counter Muscle Atrophy J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2003; 58(10): M923 - 926. [Abstract] [Full Text] [PDF]

				E. R. Barton-Davis, D. I. Shoturma, A. Musaro, N. Rosenthal, and H. L. Sweeney Viral mediated expression of insulin-like growth factor I blocks the aging-related loss of skeletal muscle function PNAS, December 22, 1998; 95(26): 15603 - 15607. [Abstract] [Full Text] [PDF]

				D. S. Criswell, F. W. Booth, F. DeMayo, R. J. Schwartz, S. E. Gordon, and M. L. Fiorotto Overexpression of IGF-I in skeletal muscle of transgenic mice does not prevent unloading-induced atrophy Am J Physiol Endocrinol Metab, September 1, 1998; 275(3): E373 - E379. [Abstract] [Full Text] [PDF]

				E. R. Barton, L. Morris, A. Musaro, N. Rosenthal, and H. L. Sweeney Muscle-specific expression of insulin-like growth factor I counters muscle decline in mdx mice J. Cell Biol., April 1, 2002; 157(1): 137 - 148. [Abstract] [Full Text] [PDF]