Every now and then a paper gets published that makes me react with a mixture of “Finally” and “I told you so”. Last week as I was going through my feeds I came across one of such articles.
The last sentence of the abstract immediately caught my attention:
“Neuroglial signaling in the adult brain may therefore occur in a manner fundamentally distinct from that exhibited during development.”
The article looks at how glia and neurons interact during synaptic transmission. There has been a lot of research showing that glia are not just the passive support structures they were previously thought to be, but that they instead play a rather active role in nerve communication in collaboration with the better known neurons in the brain. How (or rather when) this happens is what is challenged by Sun and his collaborators .
They note that, mostly, the view that astrocytes (a type of glia) respond to one of the chemicals that is used for communication between neurons (glutamate) is not based on results from adult brains. By comparing the responses of astrocytes in young and adult brains, the authors reach the conclusion that things actually change with age. In young animals astrocytes responded to chemicals that bind to one type of glutamate receptor by increasing intracellular calcium (as expected), but this did not happen in adult brains.
Of course, this study only looks at the changes with age in astrocyte behaviour with respect to one receptor (called mGluR5), so there is still more work to be done. But it was a nice article to find, as I am becoming more interested in glia lately. As I have been reading the literature and talking to people, I have often been troubled by how often reports from young mammals are used as proxies for what happens in adults. And this tendency is even stronger in more informal tea-room conversations. So at least now I have something to refer to when the first thing that comes to mind is “but….”.
Antje Grosche and Andreas Reichenback have a nice perspective on the article, also published in Science 
 Sun, W., McConnell, E., Pare, J.-F., Xu, Q., Chen, M., Peng, W., Lovatt, D., Han, X., Smith, Y. Nedergaard, M. (2013). Glutamate-Dependent Neuroglial Calcium Signaling Differs Between Young and Adult Brain. Science, 339(6116), 197–200. doi:10.1126/science.1226740
 Grosche, A., & Reichenbach, A. (2013). Developmental Refining of Neuroglial Signaling? Science, 339(6116), 152–153. doi:10.1126/science.1233208