Abstract 1. 1.|Norepinephrine (NE) and dopamine (DA) levels in various brain regions were measured in a model of experimentally produced convulsions by monosodium l-glutamate (MSG) administration to adult rats. 2. 2.|Stress by injection of all solutions produced a 60% decrease in NE level in forebrain, recovering its basal value at 15 min after injection. 3. 3.|A significant reduction of brain NE and DA levels of MSG-injected animals was found in the preconvulsive stage, particularly in the forebrain. 4. 4.|No significant variations in catecholamine levels were seen in brain stem and cerebellum as a result of MSG injection. 5. 5.|It is suggested that the changes found in endogenous catecholamine concentration in the forebrain may play a physiological role in the mechanisms of production of convulsions in the MSG model.