Effect of muscimol and picrotoxin injection in am and ac nucleus of amygdala on aggressive behavior

Aggressive behavior is a major issue in the field of mental health. Pharmacotherapy is often used for the treatment of violent individuals. A neurochemical system most consistently linked with aggression is the GABAergic system. The aim of the present investigation was to examine the effect of muscimol (GABAA agonist) 250 and 500 ng/rat and picrotoxin (GABAA antagonist) 1.5 and 3 ng/rat injection into central amygdaloid (ac) and medial amygdaloid (am) nuclei of amygdala on aggressive behavior. Fifty five adult male rats weighting 180 to 220 g were used. Cannulae were implanted into the ac and am nuclei of amygdala using stereotaxic method. Aggression was induced by applying 2 mA current every 3 seconds for 5 minutes. After the electrical shock, another rat was placed in the electroshock chamber, and the behavior of aggressive rat was evaluated in comparison to the normal one. Data were analyzed by one way analysis of variance ANOVA and Tukey as post-hoc test and Student T test. Level of significance was set at P<0.05. Data showed that injection of muscimol (500 ng/rat) into the ac and am nuclei of amygdala significantly increased aggressive behavior (P<0.05). Injection of picrotoxin (1.5 ng/rat) into the ac nucleus of amygdala significantly increased the aggressive behavior, too (P<0.05). Furthermore, injection of picrotoxin (1.5 and 3 ng/rat) into the am nucleus of amygdala significantly increased aggressive behavior (P<0.05). It can be deduced that GABA system in the ac nucleus of amygdale is more potent than the am nucleus; and both ac and am nuclei of amygdala modulate aggressive behavior mediated by GABAA receptors.