MODULATION OF LEARNING AND NEURONAL MEMBRANE-COMPOSITION IN THE RAT BY ESSENTIAL FATTY-ACID PREPARATION - TIME-COURSE ANALYSIS

Previous studies have shown that chronic administration of SR-3 (a 1:4 mixture of alpha-linolenic and linoleic acid) affects spatial learnin g, thermoregulation, pain threshold and protection from seizures. The mode of action is unknown. One possible explanation is that the prepar ation induces changes in the fatty acids profile and in the cholestero l level in the neuronal membrane. This study used 15 independent group s of rats (n = 12) which were given either saline, mineral oil (vehicl e) or SR-3 (25 mg/kg) for 0, 1, 2, 3, or 4 weeks. The learning perform ance was measured in the Morris Water tank and the fatty acids profile and the cholesterol level were examined by the GC method in synaptoso mes obtained from the frontal cortex of the rats. SR-3 improved the le arning performance and induced major changes in the neuronal membrane composition, such as an increase in the total level of fatty acids, an increase in the level of essential fatty acids and a decrease in the cholesterol level. Those changes occurred after 3 weeks of treatment. The biochemical variables can predict the behavioral variables but not vice versa. The changes in the neuronal membrane may result in a modi fication of the membrane fluidity, which may, in turn, enhance cogniti ve and neuropharmacological effects.