'Uncontrolled brain activity' linked to epilepsy

Researchers have shed new light on the mechanism behind epilepsy attacks in the brain, revealing a potential new target for drug treatment. Around half a million people in the UK have some form of epilepsy. Until recently the focus of research has been on cells called neurons, but a US study points to a completely different cell.

Nature Neuroscience journal reports its behaviour may be key to uncontrolled brain activity behind the condition. Epilepsy attacks, which can manifest as fits in some people, or "absences" in others, are caused by too much electrical signalling from the brain's neurons. However, in many cases, the reason for this over-activity is poorly understood.

Scientists now believe that, in some cases, although the problem happens at the neuron the underlying reason may be the failure of surrounding cells to help control this activity. The latest study, from the Tuft University School of Medicine and the Children's Hospital of Philadelphia, provides the strongest evidence yet that a cell called an astrocyte is the culprit.

The astrocyte is known to have a wide range of functions, including supplying nutrients to other brain cells, and even helping the brain cope with damaged nerve cells. In some brain diseases, the astrocytes swell up and behave differently, and it is this condition which the researchers believe is linked to epilepsy.

They induced this swelling in brain samples from mice, then tested whether this made a difference to the ability of the brain cells to "turn down", or inhibit, the brain signals from specific neurons. They found that the enlarged astrocytes led to reduced levels of a brain chemical known to inhibit electrical signalling from the neurons.

Dr Douglas Coulter, one of the researchers, said: "We already know that inhibition is a powerful force in the brain. "In epilepsy, inhibition is not working properly, and uncontrolled signalling leads to epileptic seizures. By better understanding the detailed events that occur in epilepsy, we are gaining knowledge that could ultimately lead to better treatments for epilepsy, and possibly for other neurological diseases."

Professor Vincenzo Crunelli, a neuroscientist from the University of Cardiff, said other research, including his own, now pointed towards a role for astrocytes in various different types of epilepsy. He said the finding might be particularly relevant in a form of epilepsy called temporal lobe epilepsy, which can be resistant to treatment. He said: "This certainly suggests that the astrocytes may be involved in maintaining this over-excitation of the neurons. If this is the case, it offers the chance of a new therapeutic target."

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