August 14, 2014

Astrocytes used to be the red-headed stepchild of the neurobiology world, but no more! Once considered to be just filler material, astrocytes are now known to function in the development and function of synapses, though the mechanisms are unclear. Today’s stunning image is from a paper showing how astrocytes can stabilize synapses, possibly serving as an important component of learning and memory. 

The synapses of neurons in the central nervous system are dynamic in response to learning and memory. The synapses are enveloped by perisynaptic astrocytic processes (PAPs), which are intricate processes of astrocytes. This close association of PAPs with synapses suggests an important role for astrocytes in synaptic development, transmission, and plasticity—the focus of a recent paper by Bernardinelli and colleagues. In this study, time-lapse imaging of brain slices revealed that long-term potentiation increased PAP motility and astrocyte coverage of the synapse. In vivo imaging of the somatosensory cortex of adult mice after whisker stimulation showed an increase in PAP motility, and later dendritic spine stability. From these results, Bernardinelli and colleagues identify a novel bidirectional interaction between PAPs and synapses, in which synaptic activity regulates PAP plasticity, which in turn regulates PAP coverage of synapses and long-term spine survival. The image above shows CA1 neurons (green) and stratum radiatum astroctyes (red) in mouse hippocampal tissue.

Bernardinelli, Y., Randall, J., Janett, E., Nikonenko, I., König, S., Jones, E., Flores, C., Murai, K., Bochet, C., Holtmaat, A., & Muller, D. (2014). Activity-Dependent Structural Plasticity of Perisynaptic Astrocytic Domains Promotes Excitatory Synapse Stability Current Biology, 24 (15), 1679-1688 DOI: 10.1016/j.cub.2014.06.025
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