I’ve just finished reading a really interesting article from last year’s Archives of General Psychiatry on GABA receptors in people with anxiety (Cameron et al, 2007). The GABA receptor is found throughout the brain. GABA itself is thought of as the major inhibitory neurotransmitter, dampening down activity in neurons. Drugs such as the benzodiazepines are thought to relieve anxiety by acting on GABA receptors. One idea is that people with anxiety might not be able to inhibit excited neurons as well as people without anxiety. With this in mind, the investigators used a sophisticated imaging technique known as PET scanning. The PET scanner uses gamma rays to picture the brain. The team used radioactive flumazenil, which binds to GABA receptors. The study involved 32 subjects – 11 with panic disorder and 21 healthy controls.
When they imaged the brains of controls and people with panic attacks, they found a big difference in part of the brain known as the Insular Cortex. This is an interesting and complex part of the brain which seems to be involved in sensation, motor regulation and emotions. They found that the people with panic had less activity in this area and suggested a number of reasons for this. People with panic disorder might have less neurons with GABA receptors, they might have less GABA receptors or they might have large numbers of other types of neurotransmitters which bind instead.
This was a surprising result as no-one had commented on the insular cortex in this type of study before. The researchers were expecting to find differences in other parts of the limbic system (the part of the brain thought to be involved in emotion) but didn’t find any. This study builds up a picture of what might be happening in people who experience panic attacks. However, it will be even more satisfying if this can be built into a model which includes our psychological understanding of how the brain works.
Cameron O, Huang G, Nichols T, Koeppe R, Minoshima S, Rose D and Frey K. Reduced GABAa-Benzodiazepine Binding Sites in Insular Cortex of Individuals with Panic Disorder. Arch Gen Psychiatry. 2007. 64(7). 793-800.
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