The Importance of Astrocytes
Posted on January 17, 2006Scientists have discovered that astrocytes act independently of neurons to connect with blood vessels and control the flow of nutrients and oxygen in the brain. A LiveScience.com article discusses the new findings that were reported in Nature Neuroscience.
Astrocytes produce fat-like lipid neurons used to create their outer membranes and they also produce glutamate, the most abundant neurotransmitter in the nervous system and one of the most important chemical messengers in the brain.Astrocytes may be one of the keys to the brain repairing after brain damage and to finding cures for alzheimer's and dimensia.
Recent experiments, however, revealed that astrocytes form connections with blood vessels and control the flow of nutrients, including oxygen, to neurons. When brain activity increases, neurons trigger astrocytes to release calcium, which in turn affects other chemical messengers that can cause blood vessels to either dilate or contract.
The classical symptoms of memory loss and dementia associated with Alzheimer's are the result of neurons dying over a period of years. Brain scans of Alzheimer's patients show decreased blood flow to critical parts of the brain, and doctors have always assumed that this was because there was less of a demand for blood because there were fewer neurons to feed.Healthy astrocytes equals healthy neurons it would seem.
The new result could mean that Alzheimer's affects mainly astrocytes and not neurons and that blood flow to the brain is not decreased because the neurons are dying, but that the neurons are dying because there is decreased blood flow.
"It may be that for whatever reason, astrocytes are not doing their job properly, and then blood flow decreases," Nedergaard said. "This could lead to the death of the neurons, which would starve from a lack of nutrients, since the neurons depend on the astrocytes for their survival."