By Sean Henahan, Access Excellence

BALTIMORE (4/22/96)- The discovery of molecular gatekeeper involving memory function offers new opportunities for development treatments for stroke and neurological disorders, report scientists at Johns Hopkins Universty.

The scientists discovered that calmodulin, a common molecule found in all nerve cells, can shut important cell "gates," stemming a flow of calcium involved in creating memory that also can contribute to stroke damage.

The discovery advances efforts to understand how the brain creates memories by altering nerve cells, and may lead to new possibilities for treatment of strokes and other disorders, according to Michael Ehlers, a Johns Hopkins M.D./Ph.D. student. Ehlers won a Hopkins Young Investigators' Day Award for his role in the new discovery.

Working in the labs of Richard Huganir, Ph.D., a professor of neuroscience at Johns Hopkins, Ehlers learned that calmodulin, a molecule common to nerve cells, can slam shut gates on the surface of nerve cells that allow chemicals to flow into the cells.

When these gates, called NMDA glutamate receptors, open briefly, nerve cells are stimulated, producing a chain reaction that results in the creation or transmission of a message to another nerve cell.

If the nerves are rapidly stimulated in a short period of time, a magnesium "bolt" can be knocked off the gate, allowing calcium ions to flow more freely into the nerve. Depending on how many calcium ions flow in, the nerve cell may become a quicker and stronger transmitter of messages or a slower and weaker transmitter. Scientists call this synaptic plasticity, and believe it is an important way the brain creates learning and memory.

"Now that we know that calmodulin can affect this process, this could provide us with a possible mechanism for controlling whether nerves become stronger or weaker transmitters of messages. This might one day help us improve learning and memory," says Ehlers.

Researchers also think that NMDA receptors jam during a stroke in their full open position, allowing the nerve cell to absorb a fatal dose of calcium. Because calmodulin is found in most nerve cells, it may be a potent tool for researchers trying to close NMDA receptors and prevent nerve cell death.

The findings were published in Cell.

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