Reversibility of n-3 fatty acid deficiency-induced alterations of learning behavior in the rat: level of n-6 fatty acids as another critical factor

• Published in: Journal of lipid research Vol. 42; no. 10; pp. 1655 - 1663
• Main Authors: Ikemoto, A, Ohishi, M, Sato, Y, Hata, N, Misawa, Y, Fujii, Y, Okuyama, H
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01.10.2001
• Subjects: Aging - physiology; alpha-Linolenic Acid - administration & dosage; alpha-Linolenic Acid - pharmacology; Animals; arachidonic acid; brain; Central Nervous System - chemistry; Central Nervous System - drug effects; Central Nervous System - metabolism; Dietary Fats, Unsaturated - administration & dosage; Dietary Fats, Unsaturated - pharmacology; docosahexaenoic acid; Docosahexaenoic Acids - administration & dosage; Docosahexaenoic Acids - pharmacology; Fatty Acids, Omega-3 - administration & dosage; Fatty Acids, Omega-3 - analysis; Fatty Acids, Omega-3 - pharmacology; Fatty Acids, Omega-6; Fatty Acids, Unsaturated - administration & dosage; Fatty Acids, Unsaturated - analysis; Fatty Acids, Unsaturated - deficiency; Fatty Acids, Unsaturated - pharmacology; Female; Learning - drug effects; learning ability; Light; linoleic acid; Neuropsychological Tests; Photic Stimulation; Plant Oils; Rats; Reinforcement, Psychology; Safflower Oil - administration & dosage; Safflower Oil - pharmacology; Visual Perception - drug effects; Weaning; α-linolenic acid
• ISSN: 0022-2275
• DOI: 10.1016/s0022-2275(20)32220-3

Rats fed a semipurified diet supplemented with 3% (w/w) safflower oil [Saf, n-3 fatty acid deficient, high linoleic acid (18:2n-6)] through two generations exhibit decreased correct response ratios in a brightness-discrimination learning test compared with rats fed 3% perilla oil [Per, high alpha-linolenic acid (18:3n-3)]. This is associated with a decreased DHA (22:6n-3)-to-arachidonic acid (20:4n-6) ratio in brain lipids. In the first set of experiments, dietary oil was shifted from Saf to a mixture of 2.4% safflower oil plus 0.6% DHA after weaning (Saf-DHA), but all parameters measured in the learning test were essentially unchanged. Brain 22:6n-3 content of the Saf-DHA group reached that of the Per group but the levels of 20:4n-6 and docosatetraenoic acid (22:4n-6) did not decrease to those of the Per group at the start of the test. In the second set of experiments, dietary oil was shifted to a mixture of 0.6% safflower oil plus 1.2% oleic acid (OA) plus 1.2% DHA (Saf-OA-DHA group) with 18:2n-6 content comparable to that of the Per group. The Saf-OA-DHA group exhibited a learning performance similar to that of the Per group; brain 22:6n-3, 20:4n-6, and 22:4n-6 contents were also comparable to those of the Per group. These results indicate that the altered learning behavior associated with a long-term n-3 fatty acid deficiency is reversed by supplementing 22:6n-3 after weaning, when the levels of competing n-6 fatty acids in the diet and brain lipids are limited.