The nogo gene encodes at least three different proteins, which share a high C-terminal homology with other members of the Reticulon family. Nogo (Reticulon 4) expression has been studied in innervated and denervated mouse hind-limb and hemidiaphragm muscles. A common Nogo A, B, and C probe hybridized to three transcripts, in accordance with human and rat data. Denervation caused decreased Nogo C and increased Nogo A mRNA expression, while Nogo B was not substantially altered. Western blots and immunohistochemistry confirmed the presence of Nogo A-like and Nogo B-like immunoreactivity in muscle. Nogo A-like immunoreactivity increased after denervation and was also present in intramuscular nerves in both innervated and denervated muscle. Nogo B-like immunoreactivity was observed in connective tissue surrounding muscle fibres and nerves. The different Nogo transcripts are produced by both alternative splicing (A and B) and alternative promoter usage (C); both mechanisms seem to be under neural control in skeletal muscle.