Situations of stress are capable of inducing depression and oxidative stress in the brain. Previous reports have shown that angiotensin II (Ang II) induces the production of superoxide anion (O(2)(-)), and impairment of endothelial function in cerebral microvessels in vivo. Substances that reduce angiotensin functions may be important in the treatment of depression. These data suggest a role for both Ang II and O(2)(-) in depression; thus, the aim of this study was to determine the effect of forced swimming test (FST), a model of stress/depression, on the cellular expression of Ang II and O(2)(-) in the central nervous system. To induce stress/depression, rats were subjected to FST daily (30 min) for 15 days. Unstressed animals were used as controls. Motor activity was automatically analyzed daily before swimming. Cerebrum and cerebellum frozen sections were studied for O(2)(-) by a histochemical method and for Ang II producing cells by a polyclonal antibody. In the FST group, struggle time, total horizontal activity, ambulatory movements, and vertical movements, were significantly decreased when the data from the 1st and 15th day were compared. Food intake and body weight gain also decreased when unstressed and FST rats were compared at the 15th day. Increased number of cerebrum and cerebellum O(2)(-), and Ang II positive cells, were observed in FST rats. Significant correlation was found between O(2)(-) positive cells and Ang II positive cell in the cerebrum. These results suggest that stress/depression situations could be involved in the increase of Ang II and oxidative stress in the central nervous system, with possible implications in the depressive condition.