BACKGROUND:Tyrosine hydroxylase and phenylethanolamine-n-methyl transferase expression coexist in Purkinje cells of the rat cerebellum.Numerous reports have also been published addressing whether dopamine-beta-hydroxylase(DBH) expression exists in cerebellar Purkinje cells. OBJECTIVE:To investigate the coexistence of DBH and activator protein-2αexpression in rat cerebellar Purkinje cells. DESIGN,TIME AND SETTING:A cell morphological study was performed at the Institute of Neuroscience,Chongqing Medical University,China in May 2007. MATERIALS:Ten healthy Wistar rats,of either gender,aged 14 weeks,served as experimental animals.Rabbit anti-mouse DBH,goat anti-mouse activator protein-2αand rabbit anti-mouseβ-actin (Santa Cruz Biotechnology,Inc.,USA),horseradish peroxidase-labeled goat anti-rabbit IgG, FITC-labeled mouse anti-rabbit IgG,and Cy3-labeled mouse anti-goat IgG(Boster,Wuhan,China), were used in this study. METHODS:Immunohistochemical staining was used to measure the expression of DBH or activator protein-2α,with double-label immunofluorescence being employed to determine coexpression of both,in the cerebellum of 5 randomly selected rats.Western blot assay was utilized to determine the expression of DBH and activator protein-2αin the cerebellum of the remaining 5 rats. MAIN OUTCOME MEASURES:Expression,localization and coexistence of DBH and activator protein-2αin the cerebellum were measured separately. RESULTS:Immunohistochemical staining demonstrated that cerebellar Purkinje cells stained positive for DBH and activator protein-2α.Western blot assay also demonstrated DBH and activator protein-2αexpression in the cerebellum.Double-labeling immunofluorescence showed the coexistence of DBH and activator protein-2αin cerebellar Purkinje cells. CONCLUSION:Norepinephrine and activator protein-2αcoexist in rat cerebellar Purkinje cells.