Astrocytic regulation of neuronal synchronization. The function that astrocytic glia play is poorly understood, and their traditional role, as supportive of neurons, captures only a small part of many functional outputs that astrocytes may have. Recent research on astrocytes has revealed important effects on synaptic transmission, but their role in the circuit as a whole has been less studied, partly due to lack of circuit-level assays of the interaction between astrocytes and neurons. Using two-photon imaging, we have recently discovered that, in neocortical brain slices, stimulation of a single astrocyte can lead t widespread neuronal synchronization, in the form of UP states. Conversely, blocking astrocytic signaling by the injection of BAPTA into individual astrocytes can reduce the number of spontaneous neuronal UP states. We propose to test in a series of direct experiments if astrocytes regulate UP states in vivo. We have developed new two-photon and genetic techniques that enable us to image and manipulate the activity of astrocytes in vivo and examine how it relates to neuronal UP states. Our central hypothesis is that the activity of astrocytes precedes, and is causally related, to the occurrence of UP states. Specifically, in a first aim we will perform fast two-photon calcium imaging, with SLMs, of neuronal and astrocytic activity during UP states in Brainbow mice where astrocytic territories are labeled, and examine whether there are spatio- temporal correlations between the activity of astrocytes and neurons. In a second aim we will optically stimulate astrocytes, using two-photon uncaging of RuBi- glutamate, IP3 or ChR2 photoactivation, and test whether this increases or alters spontaneous UP states. Our proposed work could establish a causal link between astrocytic function and neuronal synchronization in vivo, thus providing a novel circuit-level functional role for astrocytes. UP states are thought to underlie slow-wave sleep and "resting state" fMRI signals, so our research could directly involve astrocytes in the circuit mechanisms of those global brain states. Our group has a unique combination of optical and circuit neuroscience skills and this research could introduce novel approaches into the study of astroglia.

Public Health Relevance

Astrocytic glia are a poorly understood cell type that could hold the key for many brain processes and diseases. We have recently discovered in neocortical brain slices that stimulation of astrocytes can lead to the synchronization of neurons. We now want to test if this is the case in vivo, because this could directly reveal the role that astrocytes play in the function of the cortical circuits. !

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21DA034195-01
Application #
8355633
Study Section
Cellular and Molecular Biology of Glia Study Section (CMBG)
Program Officer
Sorensen, Roger
Project Start
2013-02-01
Project End
2015-01-31
Budget Start
2013-02-01
Budget End
2014-01-31
Support Year
1
Fiscal Year
2013
Total Cost
$240,000
Indirect Cost
$90,000
Name
Columbia University (N.Y.)
Department
Biology
Type
Other Domestic Higher Education
DUNS #
049179401
City
New York
State
NY
Country
United States
Zip Code
10027
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Izquierdo-Serra, Mercè; Gascón-Moya, Marta; Hirtz, Jan J et al. (2014) Two-photon neuronal and astrocytic stimulation with azobenzene-based photoswitches. J Am Chem Soc 136:8693-701
Araya, Roberto; Vogels, Tim P; Yuste, Rafael (2014) Activity-dependent dendritic spine neck changes are correlated with synaptic strength. Proc Natl Acad Sci U S A 111:E2895-904