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Interactions between the total blood calcium level and catecholamine contents in limbic brain structures during the formation and extinction of a conditioned passive avoidance reflex were studied in rats with hypoparathyroidism. Impairments of calcium support for the processes of conditioned reflex activity were seen after removal of the parathyroid glands. Animals with hypoparathyroidism not only showed changes in basal dopamine and noradrenaline levels in limbic structures, but also impairments of catecholamine dynamics during the acquisition and forced extinction of a conditioned passive avoidance reflex. These results demonstrate changes in the functional dynamics of the dopaminergic and noradrenergic systems of the brain in conditions of abnormal calcium homeostasis in the body, which underlie abnormalities of conditioned reflex activity and the acquisition of the adaptive behavioral strategies.