If, as in epilepsy, a particular channel shows up where it is not supposed to or appears in too many or too few numbers, the function that channel is responsible for can become abnormal. Researchers know that during epileptic seizures, these calcium channels in the brain, responsible for generating electrical brain rhythms, become highly active.
For the study, researchers used a mouse model to observe changes in tissue from regions of the brain that are involved in seizures, the hippocampus and the thalamus. They measured these changes at different time intervals as the mice developed epilepsy. The researchers found that after an initial seizure, more of this particular kind of calcium channel begins to be expressed where it wasn't before, and the presence of the channel caused brain activity to become increasingly abnormal and epileptic.
"Calcium channels underlie valuable functions," Godwin said. "But in the wrong place, at the wrong time, or in the wrong amount, their presence can be disruptive. In the context of brain circuits, the brain cells that have too many copies of the channel get over excited and respond abnormally."
While the hippocampus is usually targeted in studies of epilepsy, the new channels were being made in a region of the brain called the thalamus. The thalamus is connected to the hippocampus and is involved in the spread of seizures throughout the brain.
"Certain kinds of channels are normal and expected in the thalamus, but after an initial seizure more copies of a channel that isn't normally found in this brain region begin to appear," explained graduate student John Graef, the first author on the study. "The brain activity then becomes dominated by the new copies of this channel. It helps explain how seizures can develop and spread."
The particular gene that codes for the misplaced channel has been called a "susceptibility gene"
|Contact: Jessica Guenzel|
Wake Forest University Baptist Medical Center