Analyzing the Size, Shape, and Directionality of Networks of Coupled Astrocytes.

Steven Condamine, Dorly Verdier, Arlette Kolta
JoVE. 2018-10-04; (140):
DOI: 10.3791/58116

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It has become increasingly clear that astrocytes modulate neuronal function not
only at the synaptic and single-cell levels, but also at the network level.
Astrocytes are strongly connected to each other through gap junctions and
coupling through these junctions is dynamic and highly regulated. An emerging
concept is that astrocytic functions are specialized and adapted to the functions
of the neuronal circuit with which they are associated. Therefore, methods to
measure various parameters of astrocytic networks are needed to better describe
the rules governing their communication and coupling and to further understand
their functions. Here, using the image analysis software (e.g., ImageJFIJI), we
describe a method to analyze confocal images of astrocytic networks revealed by
dye-coupling. These methods allow for 1) an automated and unbiased detection of
labeled cells, 2) calculation of the size of the network, 3) computation of the
preferential orientation of dye spread within the network, and 4) repositioning
of the network within the area of interest. This analysis can be used to
characterize astrocytic networks of a particular area, compare networks of
different areas associated to different functions, or compare networks obtained
under different conditions that have different effects on coupling. These
observations may lead to important functional considerations. For instance, we
analyze the astrocytic networks of a trigeminal nucleus, where we have previously
shown that astrocytic coupling is essential for the ability of neurons to switch
their firing patterns from tonic to rhythmic bursting1. By measuring the size,
confinement, and preferential orientation of astrocytic networks in this nucleus,
we can build hypotheses about functional domains that they circumscribe. Several
studies suggest that several other brain areas, including the barrel cortex,
lateral superior olive, olfactory glomeruli, and sensory nuclei in the thalamus
and visual cortex, to name a few, may benefit from a similar analysis.


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