In adults, epilepsy is caused by hyperactivation of neuronal receptors triggered by the neurotransmitter glutamate. This excess activation unleashes the storm of uncontrolled nerve cell firing that underlies epilepsy. In contrast, in adults the neurotransmitter GABA acts on its receptors to inhibit neurons. Loss of this inhibition is also involved in epilepsy.
Neurotransmitters such as glutamate and GABA are chemical signals that one neuron launches at its neighbor across connections called synapses.
Yehezkel Ben-Ari and colleagues decided to explore a possible role of GABA-controlled neural circuitry in seizures in infant animals because it was known that, while GABA excites immature neurons, it changes to an inhibitory neurotransmitter in adult neurons.
In their experiments described in the December 8, 2005, issue of Neuron, they used a preparation in which they isolated in three separate compartments the left and right hippocampi of baby rats and the nerve fibers connecting them. The researchers studied the hippocampus because it is the brain area central to epilepsy.
With this experimental arrangement, they could use drugs to block GABA receptors and/or induce electrical seizure in one hippocampus and analyze whether such manipulations influenced seizure activity in the other. Such a spreading influence is a sign that individual seizures have caused development of a chronic epileptic state.