Protective effects of dietary docosahexaenoic acid against kainate-induced retinal degeneration in rats.
OBJECTIVE
To investigate the role played by docosahexaenoic acid (DHA) in the retina, and more specifically, its ability to protect the retina from kainic acid (KA)-induced retinal damage.


METHODS
Three-week-old female Wistar rats were used. DHA (1000 mg/kg per day) was fed to the rats for 7, 14, and 28 days, and the concentrations of DHA and arachidonic acid (AA) in the retina and serum were measured. In another group of rats, the right eyes were injected intravitreally with 3.12 nanomoles KA after DHA supplementation for 14 days. Electroretinograms (ERGs) elicited by different stimulus intensities were recorded before and on days 1, 7, and 14 after the KA injection. The amplitudes and implicit times of the a- and b-waves were compared. The number of cells in the ganglion cell layer (GCL) and inner nuclear layer (INL) were compared by histopathologic examination.


RESULTS
The concentration of DHA in the serum and retina increased after DHA supplementation. The concentration of AA in serum decreased with DHA supplementation, but the concentration of AA in retina did not show any significant change. The b-waves of the ERGs recorded after KA injection were significantly attenuated in both groups of rats. However, the attenuation was significantly less in the DHA-supplemented rats than in gum arabic-supplemented control rats. The numbers of cells in the INL and GCL were significantly higher in DHA-supplemented rats.


CONCLUSIONS
These results indicate that DHA supplementation can partially counteract KA neurotoxicity in the rat retina. DHA may play a role in modulating neuronal excitability by reducing KA-induced responses in the retina.
Mizota
A
A
Department of Ophthalmology, Chiba University School of Medicine. Central Research Institute Maruha Corp., Tsukuba, Japan. mizota@ophthalm.m.chiba-u.ac.jp
Sato
E
E
Taniai
M
M
Adachi-Usami
E
E
Nishikawa
M
M
D000818:Animals; D016718:Arachidonic Acid / Q000097:blood; D004042:Dietary Fats, Unsaturated / Q000008:administration & dosage* / Q000097:blood; D004281:Docosahexaenoic Acids / Q000008:administration & dosage* / Q000097:blood; D004596:Electroretinography; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity*; D005260:Female; D007608:Kainic Acid / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D012162:Retinal Degeneration / Q000139:chemically induced / Q000503:physiopathology / Q000517:prevention & control*
D004042:Dietary Fats, Unsaturated; D018690:Excitatory Amino Acid Agonists; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D007608:Kainic Acid