A diet low in omega-3 fatty acids — typically found in fish oils — has been associated with mood disorders. To find a molecular link, Sophie Layé at the University of Bordeaux in France, Olivier Manzoni at the French National Institute of Health and Medical Research in Marseilles and their co-workers fed mice a diet that was either high or low in omega-3s. They then looked at the ability of neurons in the prefrontal cortex, a brain region thought to mediate emotional behaviour, to alter the strength of their connections — a process known as synaptic plasticity. The authors focused on lipid signalling molecules called endocannabinoids and their receptors, which are involved in this process.
They found that mice whose diets were low in omega-3s had lower levels of the fats, and reduced synaptic plasticity, in the prefrontal cortex. This was due to the decoupling of the cannabinoid receptors from certain proteins that normally bind to them. Mice fed the low-omega-3 diet also showed behavioural signs of depression and anxiety.