Research ArticleGlia

Receptor-Selective Diffusion Barrier Enhances Sensitivity of Astrocytic Processes to Metabotropic Glutamate Receptor Stimulation

Sci. Signal.  03 Apr 2012:
Vol. 5, Issue 218, pp. ra27
DOI: 10.1126/scisignal.2002498

You are currently viewing the editor's summary.

View Full Text
As a service to the community, AAAS/Science has made this article free with registration.

Keeping Calcium Signals in the Processes

Although astrocytes, the most numerous form of glial cell in the brain, are electrically inexcitable, their ability to release chemical messengers and respond to such messengers with propagated calcium signals allows them to participate actively in the regulation of local blood flow and of synaptic efficacy. Here, Arizono et al. expressed a genetically encoded calcium indicator in neuron-astrocyte cocultures and hippocampal slices and found that, compared to the soma, astrocyte processes showed enhanced calcium responses to stimulation of the metabotropic glutamate receptor (mGluR). The enhanced calcium response observed in processes resulted from an increased density of mGluRs, rather than from differences in the distribution or sensitivity of the calcium release machinery. Analysis of the movement of single mGluR5s revealed a membrane barrier that selectively blocked the movement of mGluR5 between astrocyte somata and their processes. Noting that various neurological disorders are associated with abnormal calcium signaling in astrocytes, the authors speculate that the existence of this barrier—and thereby of compartmentalized calcium signals—could allow individual processes to regulate associated partners (synapses or blood vessels) independently, in the absence of a somatic calcium signal.