The rotten smell of memory: it's a gas.
Brain cells synthesize hydrogen sulfide and may use the gas for long-term potentiation, an interaction among brain cells linked to memory formation, report Kazuho Abe and Hideo Kimura of the Salk Institute for Biological Studies in San Diego in the Feb. 1 Journal of Neuroscience.
"They have very impressive evidence that hydrogen sulfide is a potential neurotransmitter. It's an exciting paper that should stimulate a lot of people's interest," comments Solomon H. Snyder of the Johns Hopkins Medical Institutions in Baltimore.
Snyder speaks from experience. Over the last 5 years, he and other investigators have stunned the neuroscience community by showing that brain cells make and use two other gases, nitric oxide and carbon monoxide.
Investigators have struggled to determine the actual roles these two diffusible gases play, however. "It's a very confusing and controversial field," observes Roger Nicoll of the Medical Center at the University of California, San Francisco.
Although other groups have found high concentrations of hydrogen sulfide in brains, they have not shown that brain cells actually make it, says Kimura. He and Abe now report the presence of a hydrogen sulfide-producing enzyme in the brain cells of rats.
In further experiments, the two investigators show that exposing slices of living brain tissue to hydrogen sulfide stimulates a cell-surface protein called the NMDA receptor. They also found that this stimulation appears to contribute to the strengthening of connections between brain cells that repeatedly signal each other, the hallmark of long-term potentiation.
Many neuroscientists contend that such strengthening helps imprint memories on the brain, says Kimura.
The two investigators have not proved conclusively that brain cells use hydrogen sulfide to communicate, cautions Elias Aizenman of the University of Pittsburgh School of Medicine. Such proof would entail disturbing the natural production of the gas, and scientists know of no compounds that can do that in living brain tissue.
In addition to looking for these inhibitory compounds, Abe and Kimura plan to genetically engineer mice that lack the enzyme. They'll then observe whether the absence of hydrogen sulfide affects a rodent's behavior.
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|Title Annotation:||hydrogen sulfide synthesized and used by brain cells for long-term potentiation|
|Article Type:||Brief Article|
|Date:||Feb 24, 1996|
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