Dietary Fish Oil Affects Monoaminergic Neurotransmission and Behavior in Rats

We studied the effects of a fish oil enriched diet on fatty acid composition of cerebral membranes and on several neurochemical and behavioral variables of monoaminergic function in rats. The frontal cortex, striatum, hippocampus and cerebellum were studied in rats fed fish oil (FPO, 50% salmon oil + 50% palm oil), which provided an (n-6)/(n-3) polyunsaturated fatty acid (PUFA) ratio of 0.14 versus 6.19 in controls fed a diet containing a mixture of African peanut oil and rapeseed oil. In the FPO group compared to the control group, the major modifications in fatty acid composition of cerebral membranes included the following: higher levels in 22:6(n-3), lower levels in 20:4(n-6) and a significantly greater proportion of phosphatidylserine. Dopamine levels were 40% greater in the frontal cortex of rats fed FPO than from those fed the control diet. In this cerebral region there was also a reduction in monoamine oxidase B (MAO-B) activity and greater binding to dopamine D2 receptors. By contrast, a lower binding to dopamine D2 receptors (−7%) was observed in the striatum. Ambulatory activity was also reduced in FPO-fed rats, possibly related to observed changes in striatal dopaminergic receptors. This suggested that the level of (n-6) PUFA, which was considerably lower in the FPO diet than in the control diet, could act on locomotion through an effect on striatal dopaminergic function, whereas the high level of (n-3) PUFA could act on cortical dopaminergic function.