Chronic administration of docosahexaenoic acid improves reference memory-related learning ability in young rats

doi:10.1016/S0306-4522(99)00107-4

Neuroscience

Volume 93, Issue 1, June 1999, Pages 237-241

https://doi.org/10.1016/S0306-4522(99)00107-4 Get rights and content

Abstract

Wistar rats were fed a fish oil-deficient diet through three generations. The young (five-week-old) male rats of the third generation were randomly divided into two groups. Over 10 weeks, one group was perorally administered docosahexaenoic acid dissolved in 5% gum Arabic solution at 300 mg/kg/day; the other group received a similar volume of vehicle alone. Five weeks after starting the administration, the rats were tested for learning ability related to two types of memory, reference memory and working memory, with the partially (four of eight) baited eight-arm radial maze. Reference memory is information that should be retained until the next trial. Working memory is information that disappears in a short time. Entries into unbaited arms and repeated entries into visited arms were defined as reference memory errors and working memory errors, respectively. Docosahexaenoic acid administration over 10 weeks significantly reduced the number of reference memory errors, without affecting the number of working memory errors, and significantly increased the docosahexaenoic acid content and the docosahexaenoic acid/arachidonic acid ratio in both the hippocampus and the cerebral cortex. In addition, the ratio demonstrated a significantly negative correlation with the number of reference memory errors.

These results suggest that chronic administration of docosahexaenoic acid is conducive to the improvement of reference memory-related learning ability, and that the docosahexaenoic acid/arachidonic acid ratio in the hippocampus or the cerebral cortex, or both, may be an indicator of learning ability.

Section snippets

Subjects

All rats were cared for and killed in accordance with the procedures outlined in the Guidelines for Animal Experimentation of Shimane Medical University, compiled from the Guidelines for Animal Experimentation of the Japanese Association for Laboratory Animal Science. Five-week-old female Wistar (Jcl : Wistar) rats (generation 1, G1), purchased from Clea Japan (Osaka, Japan), were housed in a room under controlled temperature (23±2°C), humidity (50±10% relative humidity) and light (08.00–20.00

The eight-arm radial maze task

Figure 1 shows the effect of chronic administration of DHA on reference memory-related learning ability in G3 rats. The score is expressed as mean number of RMEs for each group, with data averaged over blocks of six trials. The analysis revealed a significant main effect of blocks on the number of RMEs (F_9,126=48.7, P<0.05). However, the significant main effect of blocks disappeared after block 7, indicating that the score reached almost a plateau at block 7. There was a significant main effect

Discussion

This study investigated the effects of chronic administration of DHA on brain fatty acid profiles and spatial memory-related behavior in rats. The importance of brain DHA is also reflected in the ability to retain it during dietary deficiency of n-3 PUFAs.³¹ In weaned rats fed the n-6 series of fatty acids as the only lipid, there is no decrease in brain DHA after 100 days.²² The intake of dietary fish oil (rich in n-3 PUFAs) does not alter brain fatty acid composition in weaned rats.³⁶ Okada et

Acknowledgements

The present study was partially supported by a Grant-in-Aid for Encouragement of Young Scientists (08770046) and by a Grant-in-Aid for Research (C)(2) from The Ministry of Education, Science and Culture of Japan.

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Chronic administration of docosahexaenoic acid improves reference memory-related learning ability in young rats

Abstract

Section snippets

Subjects

The eight-arm radial maze task

Discussion

Acknowledgements

J. Nutr.

Brain Res.

Neuron

Brain Res.

Biochim. biophys. Acta

J. Lipid Res.

Brain Res.

J. biol. Chem.

Analyt. Biochem.

Neuroscience

Brain Res.

Physiol. Behav.

Behav. Brain Res.

Fedn Eur. biochem. Socs Lett.

J. Lipid Res.

Ischemic brain edema following occlusion of the middle cerebral artery in the rat—II. Alteration of the eicosanoid synthesis profile of brain microvessels

Stroke

A synaptic model of memory: long-term potentiation in the hippocampus

Nature

Excitatory amino acids in synaptic transmission in the Schaffer collateral–commissural pathway of the rat hippocampus

J. Physiol.