Carnosine Modulates Oxidative Homeostasis and Levels of Neurotransmitters in the Brain in Models of Learning with Positive and Negative Reinforcement

We compared the effects of the dipeptide carnosine on learning and the biochemical parameters in the brain of rats trained for defensive and food-procuring conditioned reflexes. In the first series, the animals were trained for active avoidance behavior; in the second series, the rats were trained for the food-procuring conditioned reflex in a modified shuttle box. After training, the hypothalamus and cortex were dissected and used for evaluation of lipid peroxidation processes and the levels of monoamine neurotransmitters. The activating effect of carnosine was observed during the entire training period of defensive training, whereas during training for the food-procuring reflex it was observed only in the first two sessions. In both training series, impairments of oxidative homeostasis were found in the brain; these were efficiently corrected with carnosine. This effect of carnosine may explain its positive influence on learning. Moreover, in both models, carnosine increased the contents of the main monoamine neurotransmitters in the hypothalamus. These data led us to the conclusion about high prospectivity of further studies of the carnosine modulatory effects in the nervous system.