The role of GABAergic and serotoninergic system (stress-limiting systems) in the changes occurring in the activity of blood and myocardial pro- and antioxidative systems, as well as in stress-induced cardiac structure damages was studied in 103 rabbits by using a model of long-term emotional stress induced by 24-hour hour electrostimulation of the hypothalamic dorsomedial nucleus during 12 days. The experiment alternated with relaxations of the same duration. A total of 5 sessions were conducted within 120 days. During early emotional stress, the increased activity of the hypothalamic stress-limiting systems was demonstrated to be followed by higher lipid peroxidation rates along with the activation of antioxidative enzymes. From electrostimulation cycle 3, there was exhaustion of the functional activity of the stress-limiting systems, followed by intensive increases in blood and myocardial primary and secondary lipid peroxidation products. After termination of the investigation, myocardial necrotic and ischemic changes were detected in all the animals.