An abiding puzzle in epilepsy research has been why infants (children less than two years old) are more susceptible to seizures than adults, and how this might affect their subsequently developing chronic epilepsy. Now researchers in France have discovered that neurones interacting with the neurotransmitter GABA are central to this link.

In adults' brains, GABA is an inhibitory neurotransmitter: it reduces the excitability of the brain. Losing this inhibition may be a cause of epilepsy. In infants' brains, some neurones are still not fully mature, and in immature neurones, GABA is an excitatory neurotransmitter. In infants' brains therefore, GABA signalling can increase electrical activity, not dampen it.

Dr Khalilov and his colleagues, at the Institut de Neurobiologie de la Méditerranée in Marseilles, and the Hôpital de la Salpêtrière in Paris, studied neurones in the hippocampus of immature rats. They looked at how they were affected by the presence or absence of GABA, and what effect electrical seizure activity had on the neuronal network. They found that neurones that are triggered by GABA are indeed involved in seizures, and also that these seizures could change the neuronal networks in the immature hippocampus to make them more susceptible to further seizures, thus transforming a "normal" network into an "epileptic" one.

This discovery is important because it establishes that seizures in newborns can lead to the development of chronic epilepsy. It also raises questions over the use of drugs that increase GABA concentrations in infants. Though these have an inhibitory effect in adults' brains, they may have quite the reverse in infants', possibly even increasing the likelihood of subsequently developing epilepsy.

This research is published in the 8 December edition of Neuron.

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