Evidence for the presence of both peroxisome proliferator-activated receptors alpha and beta in the rat spinal cord.

Abstract Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily. Different subtypes of PPARs (α, β, and γ) have been described. Their distinct physiological functions depend on their differential ligand activation profiles but also on their specific tissue expression. Previous studies have described their presence in the central nervous system. However, their expression in the adult rat spinal cord in normal physiological conditions has never been investigated. We demonstrated by using reverse-transcription-polymerase chain reaction, and Western blotting, the mRNA and protein expression of PPARα and PPARβ, but not PPARγ in cervical, thoracic, and lumbar segments of the spinal cord. Using immunohistochemistry, we also showed for the first time the specific cellular distribution of these transcription factors in the different segments of the spinal cord. In the gray matter, the distribution of PPARα was homogenous whereas PPARβ was specifically localized in motoneurons and in medial part of laminae IV, V, VI, VII, VIII, and X. These latter areas are known as nociceptive afferent pathways to supra-spinal structures such as the medulla reticular nucleus and the thalamus. In the white matter, PPARα was localized exclusively in astrocytes while PPARβ was present in oligodendrocytes. The possible functions of PPARα and PPARβ expressed in both white and gray matters of the spinal cord will be discussed but need further studies.