Astrocyte Calcium Microdomains
Astrocytes, a type of brain glial cell, are crucial for normal neuronal signaling and plasticity, and intracellular calcium signaling in astrocytes reportedly contributes to these processes. A number of pathways can induce astrocyte calcium signals, including activation of neurotransmitter receptors. These calcium events may evoke the release of gliotransmitters, alter astrocyte neurotransmitter uptake or change astrocyte metabolism; however, the precise role of astrocyte calcium signaling is controversial and unclear, particularly in awake animals in vivo. The detection of astrocyte calcium signals was recently revolutionized by the use of genetically encoded calcium indicators, which have uncovered localized calcium microdomains. Much of the field has focused on spontaneous astrocyte microdomains, but recently we characterized the astrocyte calcium response to local somatosensory circuit activation in vivo. We found that the majority of astrocyte microdomains evoked by sensory stimulation occurred in fine processes, which is likely due to the close association of astrocytic processes with nearby synapses. We have also recently shown that a subset of astrocyte microdomains rapidly follow neuronal responses to sensory stimulation, and that these microdomains occurred independently of known neuromodulator pathways and IP3 receptor 2 mediated signaling. Further questions remain regarding the mechanism of these fast astrocyte microdomains.
The long-term goals of our research program are: a) to decipher the mechanisms underlying astrocyte microdomains in vivo and b) to gain knowledge of the functional relevance of these localized signals in cortical circuits.
By decoding the calcium response profile of astrocytes, we will better comprehend their role in information processing, learning, memory and attention.