Incidence and severity of experimental allergic encephalomyelitis and cerebral prostaglandin synthesis in essential fatty acid deficient and aspirin-treated rats.

Experimental allergic encephalomyelitis (EAE) was induced in rats of the Lewis strain fed diets adequate or deficient in essential fatty acids (EFA). After induction of the disease, the diets were supplemented with aspirin (3.75 g/kg diet), and the effects of the drug on the course of EAE and on the synthesis of prostaglandin F (PGF) by brain slices from diseased animals and their Freund controls were examined. Aspirin supplementation delayed the onset of EAE in both dietary groups. EFA-deficient rats experienced an incidence and severity of the disease similar to that of aspirin-free, EFA-deficiet rats, while the EFA-adequate group showed a greater severity but not an increased incidence, compared to aspirin-free controls. Aspirin treatment led to an increased PGF production by brain slices from rats on either diet and not subjected to an immunochallenge. When the diet was deficient in EFA, challenge with antigen plus adjuvant or adjuvant alone tended to decrease PGF synthesis by brain slices, and when the diet was adequate in EFA, immunochallenge caused a marked depression on PGF synthesis. It was concluded that the PG synthetase inhibitor aspirin can alter the course of EAE in the rat, providing further evidence that PGs or related metabolites may be involved in the immune response in this disease.