Bipolar disorder, or manic depression, is a debilitating psychiatric condition characterised by alternating mania and depression, and affects about one in every hundred people worldwide. Although it is known that the condition can be treated relatively effectively using the moodstabilising drugs lithium and valproic acid, the reasons why these treatments work are poorly understood.
The authors of a new study, from Imperial College London, the University of Cambridge in the UK and the National Institutes of Mental Health in the USA, hope that their research will enable a better understanding of the condition and of how it can be treated.
The researchers compared postmortem brain tissue samples of people with manic depression with those of age and gender matched controls. The samples were taken from the dorsolateral prefrontal cortex, which controls the processes involved in higher cognitive functioning. The researchers analysed these samples using NMR spectroscopy and found that people with manic depression had different concentrations of chemicals in this area of the brain than those without.
The researchers also used rat models to see the effects of lithium and valproic acid on the metabolite makeup of non-bipolar brain tissue. They found that these drugs caused the opposite chemical changes to those seen in the bipolar brain tissue samples. Chemicals that were increased in the bipolar brain tissue were decreased in rats given the mood stabilising drugs, and vice versa.
The researchers' findings lead them to believe that an upset in the balance of different neurotransmitters known as excitatory and inhibitory neurotransmitters, which are involved in sending signals in the brain, may be central to the disorder. The study also suggests that lithium and valproic acid work by restoring the balance of these neurotransmitters in the brain. The work was published in Molecular Psychiatry (doi: 10.1038/sj.mp.4002130).