Nogo-A is known as an oligodendrocyte/myelin-associated molecule having an inhibitory effect on neurite outgrowth in the central nervous system. During development, starting from P21 Nogo-A was detected in the cytoplasm of mature oligodendrocytes with compact myelin sheaths in the rat spinal cord. COS7 cells transfected with recNogo-A displayed strong Nogo-A immunoreactivity in their cytoplasm as well as on the mitotic spindle. Nogo-A was not detected in membrane protein fractions from transfected plus biotinylated COS7 cells. Nogo-A was co-immunoprecipitated with alpha-tubulin and myelin basic protein (MBP) from rat brain tissue. These results show that Nogo-A is expressed in association with tubulin and MBP in the mature oligodendrocytes.