Co-localization of nitric oxide synthase I (NOS I) and NMDA receptor subunit 1 (NMDAR-1) at the neuromuscular junction in rat and mouse skeletal muscle

Cell Tissue Res. 1998 Jan;291(1):57-63. doi: 10.1007/s004410050979.


Nitric oxide synthase I (NOS I) has been localized to the skeletal muscle sarcolemma in a variety of vertebrate species including man. It is particularly enriched at neuromuscular junctions. Recently, the N-methyl-D-aspartate (NMDA) receptor subunit 1 (NMDAR-1) has been detected in the postjunctional sarcolemma of rat diaphragm, providing a clue as to the possible source of Ca2+ ions that are necessary for NOS I activation. To address this possibility, we studied the distribution of NMDAR-1 and NOS I in mouse and rat skeletal muscles by immunohistochemistry and enzyme histochemistry. NMDAR-1 and NOS I were closely associated at neuromuscular junctions primarily of type II muscle fibers. NOS I was also present in the extrajunctional sarcolemma of this fiber type. Dystrophin, beta-dystroglycan, alpha-sarcoglycan, and spectrin were found normally expressed in both the junctional and extrajunctional sarcolemma of both fiber types. By contrast, in the muscle sarcolemma of MDX mice, dystrophin and dystrophin-associated proteins were reduced or absent. NOS I immunoreactivity was lost from the extrajunctional sarcolemma and barely detectable in the junctional sarcolemma. NOS I activity was clearly demonstrable in the junctional sarcolemma by NADPH diaphorase histochemistry, especially when the two-step method was used. NMDAR-1 was not altered. These data suggest that different mechanisms act to attach NOS I to the junctional versus extrajunctional sarcolemma. It may further be postulated that NMDA receptors are involved not only in the regulation but also sarcolemmal targeting of NOS I at neuromuscular junctions of type II fibers. The evidence that glutamate may function as a messenger molecule at vertebrate neuromuscular junction is discussed.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cricetinae
  • Cytoskeletal Proteins / analysis
  • Dystroglycans
  • Dystrophin / deficiency
  • Female
  • Gerbillinae
  • Guinea Pigs
  • Male
  • Membrane Glycoproteins / analysis
  • Membrane Proteins / analysis
  • Mesocricetus
  • Mice
  • Mice, Inbred mdx
  • Muscle Fibers, Skeletal / chemistry
  • Muscle Fibers, Skeletal / enzymology
  • Muscle Fibers, Skeletal / ultrastructure
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / innervation*
  • Muscle, Skeletal / ultrastructure
  • Neuromuscular Junction / chemistry*
  • Neuromuscular Junction / enzymology*
  • Nitric Oxide Synthase / analysis*
  • Rats
  • Rats, Wistar
  • Receptors, N-Methyl-D-Aspartate / analysis*
  • Sarcoglycans
  • Sarcolemma / chemistry
  • Sarcolemma / enzymology
  • Species Specificity
  • Spectrin / analysis
  • Utrophin


  • Cytoskeletal Proteins
  • Dystrophin
  • Membrane Glycoproteins
  • Membrane Proteins
  • Receptors, N-Methyl-D-Aspartate
  • Sarcoglycans
  • Utrn protein, mouse
  • Utrophin
  • Spectrin
  • Dystroglycans
  • Nitric Oxide Synthase