Selective reinnervation of adult mammalian muscle by axons from different segmental levels

Abstract

The ability of axons to innervate selectively subsets of a population of largely similar target cells is undoubtedly important for the establishment of ordered patterns of neural connections. Vertebrate skeletal muscle is well suited for studies of factors that account for selective synapse formation as a wealth of information is available about the structure, function and molecular components of its neuromuscular junctions. Furthermore, skeletal muscle is readily reinnervated following nerve damage, permitting study of synaptogenesis in an accessible postembryonic environment. However, although selective synapse formation clearly occurs elsewhere in the adult peripheral nervous system^1–10, previous attempts to demonstrate selectivity in the reinnervation of mammalian muscles have been disappointing^7–15. We have now used a novel approach to reinvestigate this issue, and describe here a situation in which two different adult rat muscles are preferentially reinnervated by axons from different spinal segments. Our results suggest that adult muscles differ in some stable quality, perhaps related to their position, which influences the innervation they accept.