Mice selected for aggressiveness (long and short attack latency mice; LALs and SALs, respectively) constitute a useful tool in studying the neural background of aggressive behavior, especially so as the SAL strain shows violent forms of aggressiveness that appear abnormal in many respects. By using e-Fos staining as a marker of neuronal activation, we show here that agonistic encounters result in different activation patterns in LAL and SAL mice. In LALs, agonistic encounters activated the lateral septum, bed nucleus of stria terminalis, medial amygdala, paraventricular nucleus of the hypothalamus, anterior' hypothalamic nucleus and tuber cinereum area (both being analogous with the rat hypothalamic attack area), dorsolateral periaqueductal gray, and locus coeruleus. This pattern is similar with that seen in the territorial aggression of male mice, rats and hamsters, and non-lactating female mice. SALs showed strong fight-induced activations in the central amygdala and lateral/ ventrolateral periaqueductal gray. In this strain, no activation was seen in the lateral septum and the dorsolateral periaqueductal gray. This pattern is similar with that seen in other models of violent aggression, e.g., in attacks induced by hypothalamic stimulation in rats, quiet biting in cats, lactating female mice, and hypoarousal-driven abnormal aggression in rats. We suggest here that the excessive activation of the central amygdala and lateral/ventrolateral periaqueductal gray-accompanied by a smaller activation of the septum and dorsolateral periaqueductal gray-underlay the expression of violent attacks under various circumstances. (c) 2006 Elsevier Inc. All rights reserved.