Effects of dietary n-3 fatty acid deficiency and repletion in the guinea pig retina

PURPOSE. TO investigate the nature and reversibility of biochemical and fun ctional changes in the retina encountered over a single generation of dieta ry n-3 polyunsaturated fatty acid deficiency in guinea pigs. METHODS. Dunkin-Hartley guinea pigs mere fed for 16 weeks after weaning wit h diets supplemented with safflower seed oil (n-3 deficient) or canola oil (n-3 sufficient, control). A number of deficient animals were repleted at 6 weeks with canola oil for 5 or 10 weeks, or at 11 weeks for 5 weeks. Elect roretinograms (0.8 and 4.3 log scot td sec) were collected at 6, 11, and 16 weeks after weaning. Conventional waveforms (a- and b-waves), oscillatory potentials, and receptoral and postreceptoral subcomponents (PIII and PII, respectively) were evaluated. Cone pathway function was assessed with 30-Hz flicker at the brighter intensity. Retinal phospholipid fatty acids were m easured by capillary gas-liquid chromatography. RESULTS. Electroretinographic amplitudes showed statistically significant l osses in b- and a-waves after 6 and 16 weeks of dietary n-3 deficiency, res pectively. The response amplitude to 30-Hz flicker was reduced 42% after 16 weeks. Retinal docosahexaenoic acid (DHA) levels of animals maintained on the safflower oil diet for 16 weeks were 42% of levels in age-matched contr ol subjects. There were significant losses in maximum response amplitudes ( R-mPIII and R-mPII) although the major effect was a reduction in sensitivit y of the receptoral response. Complete functional recovery was observed onl y in animals repleted for 10 weeks. CONCLUSIONS. Functional deficits in PIII and PII of the electroretinogram w ere apparent in first-generation guinea pigs fed an n-3 deficient diet. The se losses showed a correlation with age and retinal DHA level, although var ying degrees of dependence on the DHA level were found. All functional defi cits were reversed after 10 weeks of dietary n-3 repletion. The results sug gest that DHA may serve several functional and structural roles in the reti na and further emphasize the requirement for DHA in the normal development of vision.