Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors belonging to the superfamily of steroid hormone receptors. Different subtypes of PPARs (alpha, beta and gamma) have been described, PPARalpha and PPARgamma presenting a more tissue specific distribution than PPARbeta. Specific polyclonal antibodies directed against each subtype of PPARs were produced and characterized. The general expression of PPAR proteins was investigated in rat brain and cerebellar extracts by Western blotting. In order to localize the PPAR proteins and transcripts in the cerebellum, immunocytochemical and in situ hybridization assays were performed. Our Western blot analysis revealed a 52 kDa band with the anti-PPARbeta antibody in brain and cerebellar homogenates, but no band with the anti-PPARalpha, gamma1/gamma2 and gamma2. By immunocytochemistry, a high expression of PPARbeta appeared in the nucleus of Purkinje cells. The in situ hybridization assays showed that PPARbeta transcripts were localized in the cytoplasm of the Purkinje cells. No labeling was observed for the other PPAR isoforms in the cerebellum. Purkinje cells represent the only efferent way from the cerebellar cortex and modulate spinal cord activity. The regional distribution of PPARbeta in these cells suggests some fundamental role for this subtype in this pathway.