New role identified for astrocytes in brain processing.
It is known that astrocytes are the most numerous cell type present in the brain and perform a variety of tasks, such as axon guidance, synaptic support, and homeostasis. Even though many new roles for astrocytes have been identified recently there is still much work to be done in revealing the multitude of crucial roles they play in helping the brain process information. Now, a study from researchers at the VIB-KU Leuven Center shows that noradrenaline plays a key role in how astrocytes track distinct information during behavior. The team states they found that astrocytes can integrate information on arousal state and sensory experience. The opensource study is published in the journal Current Biology.
Previous studies show when a person is aroused the hormone noradrenaline is secreted, which helps to memorize emotional situations compared to neutral ones. In earlier studies, noradrenaline was shown to directly influence synapses, information exchange points between neurons, in brain regions responsible for processing emotions. However, noradrenaline is released across the entire brain and also stimulates astrocytes, which listen and respond to locally active neurons. The current study investigates whether astrocytes integrate this brain-wide signaling with the specific activity of local neuronal networks.
The current study utilizes a special microscope to monitor the activity of astrocytes in mice. When mice were presented with visual stimuli, in some cases astrocytes responded, whereas in other cases visual stimuli did not elicit any response from the astrocytes. Results show when each event of visual stimulation was analyzed independently astrocytes were active only when the mouse was in motion, and they were silent when the mouse was stationary.
The lab then tested whether noradrenaline was the molecule responsible for this effect by using a compound which depletes the brain of noradrenaline. Data findings show that astrocytic responses were largely depressed, even when mice were in motion. The group explains that this must mean noradrenaline is necessary for astrocytes to respond to local stimulation, and that astrocytes are effectively integrating sensory and behavioral information.
The team surmises their data shows astrocytes integrate visual sensory information and behavioral states, suggesting a role in information processing. For the future, the researchers state they now plan to investigate how this operates at the molecular level and investigate the functional consequences for the brain.