BACKGROUND: Patients with type-2 diabetes mellitus exhibit higher levels of plasma endothelin-! (ET-I). However, very few reports exist regarding altered endothelin-3 (ET-3) and ET-1 concentrations in brain tissue. OBJECTIVE: To observe expression changes of ET-3 and glial fibrillary acidic protein (GFAP) in the frontal and parietal cortex of type-2 diabetic mice following ischemia-reperfusion injury, with various reperfusion durations. DESIGN, TIME AND SETTING: Randomized controlled animal study. The experiment was conducted in the Xiangya Medical College of Central South University and the Third Xiangya Hospital between February 2002 and January 2003. MATERIALS: Sixty-six, adult, male, Kunming mice, weighing (30±5) g, as well as rabbit anti-ET-3 polyclonal and rabbit anti-GFAP polyclonal antibodies, were provided by the Neurobiology Institute of Second Military Medical University in Japan. METHODS: Sixty-six mice were randomly divided into five groups: diabetes mellitus (DM, n=6), diabetes mellitus with ischemia-reperfusion (DM/IR, n = 24), ischemia-reperfusion (IR, n = 24), sham operation (SO, n = 6), and control (n = 6). MAIN OUTCOME MEASURES: Following ischemia-reperfusion for 1, 3, 5, and 10 days, respectively, expression of ET- 3 and GFAP was immunohistochemically measured in the frontal and parietal cortex. RESULTS: All 66 mice were included in the final result analysis. In the IR and DM/IR groups, ET-3- and GFAP-positive neurons increased in the frontal and parietal cortex in response to one day reperfusion, peaked at five days, and decreased at 10 days. ET-3 and GFAP expression was significantly greater in the DM/IR group after reperfusion for 1 day compared to the IR group. However, at other time points, there were no significant differences between the two groups. CONCLUSION: Brain ischemia-reperfusion injury results in overexpression of ET-3 and activation of astrocytes. Diabetes increases the number of ET-3- and GFAP-positive astrocytes in brain tissue of ischemia-reperfusion mice with the same reperfusion duration.