Myostatin (also called as growth and differentiation factor 8 or GDF8), a member of the transforming growth factor β (TGF-β) superfamily of secreted differentiation and growth factors, is a potent inhibitor of skeletal muscle mass in mammals. Although myostatin also plays pivotal roles in cardiac growth and metabolism, postnatal glucose metabolism and adipogenesis, little information is available for myostatin function in the adult central nervous system (CNS). We, thus, investigated myostatin expression in the adult rat CNS using immunohistochemistry. Myostatin was intensely expressed in most neurons and their axons. Furthermore, we found that oligodendrocytes, astrocytes and ependymal cells also express myostatin protein. These data indicate that myostatin is widely expressed throughout the adult CNS, and its abundant expression in the adult brain suggests the idea that myostatin plays important roles in the CNS.