Comparing DHA and AA dynamics -

     Competition among n-3 and n-6 fatty acids within brain probably does not occur at the level of recycling, but at levels of elongation and desaturation (hence greater production of DPA during n-3 deprivation), or conversion to bioactive eicosanoids and other metabolites. Contreras MA, Chang MC, Rosenberger TA, Greiner RS, Myers CS, Salem N Jr, Rapoport SI. Chronic nutritional deprivation of n-3 alpha-linolenic acid does not affect n-6 arachidonic acid recycling within brain phospholipids of awake rats. J Neurochem 2001 Dec;79(5):1090-9

     Rats with a dietary deficiency of alpha-linolenic acid (18:3 n-3) for three generations had plasma 22:6 n-3 at 0.2 nmol ml(-1) compared with 10.6 nmol ml(-1) in control rats. Brain docosahexaenoyl-CoA content in deficient rats was reduced by 95%, and 22:6 n-3 content in different phospholipid classes was reduced by 83-88%. [4, 5-(3)H]-Docosahexaenoic acid infused intravenously for 5 min indicated that 22:6 n-3 incorporation from plasma into brain was reduced 40-fold by the deficiency. Contreras MA, Greiner RS, Chang MC, Myers CS, Salem N Jr, Rapoport SI. Nutritional deprivation of alpha-linolenic acid decreases but does not abolish turnover and availability of unacylated docosahexaenoic acid and docosahexaenoyl-CoA in rat brain. J Neurochem 2000 Dec;75(6):2392-400.