Olfactory bulbectomy (OBX) in rats produces behavioral, physiological, and neurochemical changes that resemble symptoms of depression in humans. The procedure thus serves as a rodent model of affective disorder. Many of the behavioral effects of OBX resemble psychomotor agitation. The possible role of dysregulation of ventral striatal dopamine (DA) systems in this phenomenon was investigated. Basal levels of DA, norepinephrine (NE), homovanillic acid, dihydroxyphenylacetic acid, and 5-hydroxyindoleacetic acid were examined in the striatum of OBX and sham-operated controls using in vivo microdialysis. OBX rats exhibited significantly higher basal DA levels (192%) and lower NE levels (12%) than sham-operated controls. Locomotor activity in response to novelty and footshock stress was elevated in OBX rats. The finding of higher DA levels in striatum may explain this "agitation-like" behavior, a commonly observed phenomenon in the OBX model.