Abstract

The present study demonstrated that the omega (n)-3 fatty acid, ethyl-eicosapentaenoic acid (Ethyl-EPA), supplemented diet significantly attenuated the stress/anxiety behavior of rats in the open field and elevated plus maze, which was induced by sub-chronic intracerebroventricular administration of proinflammatory cytokine interleukin (IL)-1beta. Ethyl-EPA also reduced the rise in serum corticosterone induced by IL-1. The n-6 fatty acid, ethyl-gama-linolenic acid (GLA) had little effect on the IL-1-induced changes in behavior and the corticosterone concentration. Following IL-1beta administration, ethyl-EPA reduced the elevated prostaglandin (PG) E2 secretion, and increased the secretion of anti-inflammatory cytokine IL-10, from whole blood cells. Ethyl-GLA showed a similar anti-inflammatory effect to ethyl-EPA. By contrast, n-6 fatty acid arachidonic acid (AA) had no effect on the behaviour, immune and endocrine changes induced by IL-1. AA alone enhanced the basal inflammatory response, raised serum corticosterone concentrations and induced anxiety behaviour in the elevated plus maze. The reduced growth rate followed the administration of IL-1 was attenuated by ethyl-EPA, and to a greater extent by ethyl-EPA plus ethyl-GLA, but not by AA alone or combination with ethyl-EPA. Thus, ethyl-EPA would appear to antagonise the endocrine, immune and behavioural effects of sub-chronic IL-1 administration. Ethyl-GLA only antagonised IL-1-induced inflammatory changes, whereas AA caused an increase in the secretion of corticosterone and PGE2, and induced anxiety-like behaviour without enhancing the effects of IL-1.