Immunohistochemical expression of the alpha5 integrin subunit in the normal adult rat central nervous system.

We investigated the distribution of the alpha5 integrin subunit in the normal adult rat CNS using immunohistochemical methods. Results indicated that the alpha5 integrin subunit was expressed on the vast majority of neurons throughout the brain and spinal cord. In general, neurons showed diffuse cytoplasmic labelling, although many cortical neurons in layers 4 and 5 did show punctate labelling on the cell surface. In addition, axons within the white matter of the brainstem and caudal CNS areas were labelled, with the most intense labelling seen within the white matter of the spinal cord. In addition, labelling of astrocytes was seen throughout white matter, with particularly heavy astrocyte labelling in the spinal cord. The widespread distribution of the alpha5 subunit suggests a general function for the alpha5beta1 integrin receptor (the only integrin receptor that includes the alpha5 subunit) in the adult CNS. The increased expression of fibronectin, the only known ligand for the alpha5beta1 integrin receptor, known to occur around the site of a CNS lesion suggests a possible role for the alpha5beta1 receptor in the response of neurons in the vicinity of a CNS injury.