['To assess whether prednisone (PDN) produces anxiety and/or cerebral glial changes in rats.', 'Male Wistar rats were studied and 3 groups were formed (8 rats per group). The moderate-dose group received 5 mg/kg/day PDN released from a subcutaneous implant. In the high-dose group, implants containing PDN equivalent to 60 mg/kg/day were applied. In the control group implants contained no PDN. Anxiety was assessed using an open field and elevated plus-maze devices. The number of cells and cytoplasmic transformation of astrocytes and microglia cells were assessed by immunohistochemical analyses.', 'Anxiety was documented in both groups of PDN treated rats compared with controls. The magnitude of transformation of the microglia assessed by the number of intersections was significantly higher in the PDN groups than in controls in the prefrontal cortex (moderate-dose, 24.1; high-dose, 23.6; controls 18.7; p < 0.01) and striatum (moderate-dose 25.6; high-dose 26.3; controls 18.9; p < 0.01), but not in hippocampus. The number of stained microglia cells was significantly higher in the PDN treated groups in the prefrontal cortex than in controls (moderate-dose, 29.1; high-dose, 28.4; control, 17.7 cells per field; p < 0.01). Stained microglia cells were significantly more numerous striatum and hippocampus in the high-dose group compared to controls.'] Does prednisone induce anxiety and glial cerebral changes in rats?