SYSTEMIC administration of 3-nitropropionic acid (3NPA) in rats produces bilateral striatal lesions which are similar to those seen in Huntington's disease (HD). We examined the effects of systemic 3NPA on the expression of cytochrome oxidase (COX-II and COX-IV), succinate dehydrogenase (SDH) and astrocytic glial fibrillary acidic protein (GFAP) mRNAs and on the activity of COX and SDH as assessed by the density of histochemical staining. COX-II and COX-IV mRNA was reduced in rats with 3NPA-induced lesions, but not in those without, whereas SDH, but not COX, staining was significantly and dose-dependently reduced in both 3NPA treated groups. GFAP mRNA expression was increased in both intact striatum and cortex but was absent from the lesion core