Researchers Identify Astrocytes' New Role In Neuronal Communication
Scientists from the University of California, Los Angeles, found that brain cells called astrocytes might play a part in neuronal communication only during bursts of neuron activity.
Astrocytes have been known in recent years to play a role in neuronal communication. The levels of calcium change within brain cells once neurons release neurotransmitters. Calcium is important for many processes including activation of proteins within a cell and release of molecules. However, the role of astrocytic calcium signaling for brain functions is yet to be decoded.
Baljit S. Khakh, Ph.D., of the University of California, Los Angeles and colleagues used calcium indicator dyes to image changes in calcium levels, for the first time, in the entire astrocyte. The new method provides a new set of tools for the research community to use and extend the study’s findings, Dr. Khakh said.
The researchers focused on the mossy fiber pathway connecting two areas of the hippocampus, the brain structure responsible for learning and memory. “We found that astrocytes in the mossy fiber pathway do not listen to the constant, millisecond by millisecond synaptic chatter that neurons engage in. Instead, they listen when neurons get excessively excited during bursts of activation,” said Dr. Khakh.
Findings from the study suggest that astrocytes in the mossy fiber system may serve as a kind of switch that reacts to large amounts of neuronal activity by raising their calcium levels. However, Dr. Khakh’s findings differ from those described in other regions of the brain and suggest that astrocytes may play different roles. Dr. Khakh stated, “Astrocytes may be sitting there quietly and when there is excessive activation in the neuronal circuit, they immediately respond with an increase in calcium which we could detect. And the next big question becomes, what they do with that calcium?”
Edmund Talley, Ph.D., program director at National Institute of Neurological Disorders and Stroke (NINDS), said, “It would be really interesting and important to find that astrocytes function differently in different areas of the brain, in a circuit-specific manner. This study gives a hint that this might be true.”
The research was supported by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health. Results of the study were published in the journal Neuron.