Relative role of neural substrates in the aggressive behavior of rats

Early animal studies have shown an association between aggression and brain dysfunction. The goal of the present study was to compare the effects of lesions of different parts of brain on aggression in rats. Adult rats (n = 40, weighing 200-260 g) were randomly divided into four groups of ten animals each and subjected to lesions of the septum (Group I), medial preoptic area (Group II), medial accumbens (Group III), and bed nucleus of stria terminalis (Group IV), using stereotaxy apparatus. Aggression toward an unfamiliar male intruder was observed before and after the lesion. The aggression score of each animal was recorded three times before lesion and averaged for use in analysis. Analysis of variance (ANOVA) was applied for finding homogeneity of the groups. Postoperative scores were also similarly recorded and summarized as mean +/- standard deviation. Pre- and post-lesion scores were compared using the t test. The scores were significantly reduced in Group I, II, and III, but increased in Group IV. We can conclude that the septum, medial preoptic area, medial accumbens, and bed nucleus of stria terminalis, by virtue of their interconnections, influence aggressive behavior.