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Changes in dendrites contribute to epilepsy

by Ruth SoRelle, MPH

Daniel Johnston, PhD

Passing a message from one nerve cell to another is a complicated task. When that process goes wrong, the effect can be devastating.

Epilepsy is one disease that results from such miscommunication. Now researchers at Baylor College of Medicine in Houston think they have found a new misstep - a change in channels that allows potassium to flow through the cell membranes - that contributes to the seizure that occur in the most common form of the disorder – temporal lobe epilepsy.

This is just one new finding in an ongoing process to understand epilepsy, said Daniel Johnston, PhD, a BCM professor of neuroscience.

“There have been many theories and data suggesting that changes in the circuitry of the neurons change their state of excitation and decrease inhibition,” he said. “In a circuit of interconnected neurons, increasing one or decreasing the other causes the cells to become hyperexcitable.

“We have found that, in addition to electrical change, there are changes in the tips of cells called the dendrites,” said Johnston, “We have found that there is a decrease in the normally inhibitory ion channel in the dendrites. A report on the research appears in a recent issue of the journal Science.

He and his colleagues found that there are changes in the dendrites where synapses or the communication of information from one cell to another occurs.

“The dendrites themselves become hyperexcitable,” he said. This occurs because the channels that handle exchange of potassium through the cell membrane allow too much of the chemical to leave the cell.

“This novel finding changes the focus from synaptic excitation to the dendrites, where the synapses terminate,” he said.

Others who participated in the research include: Dr. Ann Anderson, also of Baylor; Dr. Christophe Bernard, of INSERM, U29, Marseille Ce’dex France; Dr. Albert Becker, and Dr. Heinz Beck of the University of Bonn Medical Center and Dr. Nicholas P. Poolos of the University of Washington.

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