Abstract We have isolated a new rat sequence containing motifs of a nuclear hormone receptor from a brain cDNA library. The deduced amino acid sequence encoded by the cDNA clone showed a strong homology to the human NUCI and the mouse peroxisome proliferator activated receptor δ (PPARδ). We therefore refer to this new clone as rat PPARδ (rPPARδ). The new feature of rPPARδ is a 14 CGG triplet repeat on the 5′ untranslated region, not previously reported in either NUCI or mPPARδ. We found that rPPARδ was expressed as a 3.5-kb transcript which showed a wide distribution in adult rat tissues. Abundant expression was detected in brain, heart, skeletal muscle, kidney and lung. Weaker expression was noted in the liver, spleen and testis. To determine the specific brain localization of rPPARδ we performed in situ hybridization analysis. Prominent expression was observed in the thalamus, particularly in the posterior part of the ventral medial nucleus, a site responsive to pain and cold stress. These results raise the possibility that PPARδ might play a role in modulating response to thermal and pain sensations.