Now it has been discovered that glia that make up 90 percent of our brain have essential function. This is related to successful treatment of HD with CNTF therapy because glia express CNTF and immune modulating cytokines.

Researchers seem to account for 10 percent of nature. Ten percent of the known mass of the universe is accounted for. Ten percent of the function of DNA is accounted for. The 90 percent not accounted for is sometimes thought of as unessential. --Jerry 07/19/00
Iowa State University, 19-Jul-00

Neurons, Not Only Brain Cells in Signal Transmission

AMES, Iowa -- Research conducted at Iowa State University could change our understanding of how the brain works and lead to new avenues of treatment for stroke, epilepsy and head injury.

Results of a two-year study by Iowa State neuroscientists Vladimir Parpura and Philip Haydon will appear in today's (July 18) issue of "Proceedings of the National Academy of Sciences." The paper, "Physiological Astrocytic Calcium Levels Stimulate Glutamate Release to Modulate Adjacent Neurons," gives evidence supporting a relatively new theory about communications between brain cells.

The brain has two types of cells--neurons and glia. Neurons contain neurotransmitters, which are chemicals that trigger signals to pass messages. Until recently, neuroscientists believed neurons were the only brain cells transmitting message signals. Glial cells were thought to serve only as support.

In the mid-1990s, however, Parpura and Haydon were among the first researchers to discover that glial cells are much more important to the brain's communication network than previously thought. Their 1994 paper, published in "Nature," showed that a type of glial cell--the astrocyte--releases glutamate (a neurotransmitter) and signals neurons.

"This release of glutamate is controlled by increased levels of calcium in the astrocytes. Exactly how much calcium was needed to cause the glutamate release was unclear. We didn't know if it was in the normal range for calcium levels in astrocytes. That's the question we answered in the current study," Parpura said.

Parpura and Haydon found the amount of calcium to be within the normal range, indicating that astrocytes are part of the brain's communication network.

The findings may also open new possibilities for treatment of illnesses such as stroke, epilepsy and head injury where glutamate toxicity is known to contribute to brain tissue damage, Parpura said.

"While our findings implicate astrocytes as the additional site for glutamate release under normal conditions, it is tempting to speculate that high calcium levels in astrocytes could cause excess release of glutamate, and play a role in disease," he said.

"This sheds new light on where to look for treatment. There's potential for developing new drugs that could interfere with the release of glutamate," he said.

While the research is still in its early states, Parpura said the ramifications could be great. "Neurons make up only 10 percent of the brain's cells, yet that's what we've always focused on. There's 90 percent of the brain yet to learn about. It's uncharted area," Parpura said.