174 — Gliotransmission: Beyond Black-and-White

Today’s paper is the complementary perspective to yesterday’s paper which proposed that there was sufficient evidence to suggest that astrocytes do not naturally undergo calcium-mediated neurotransmitter release.

This paper takes the opposite opinion: Glia, say the authors, not only receive information from neurons (which the field has known about for some time), but also have the ability to transmit information through neurotransmitter release.

Two studies published at the same time in 2010 reported similarly opposite opinions: Looking at LTP in hippocampus, Henneberger et al found that introducing a Ca²⁺ chelator into astrocytes blocked LTP in that region. Agulhon et al showed that transgenic disruption of a possible glial Ca²⁺ signaling pathway had no effect on LTP. Since 2010, the lines of evidence have only grown further apart.

This paper explores several different definitions of gliotransmission, challenging the assumption that it is “all-or-nothing”: That is, a glial cell need not be the only presynaptic transmitter. Any neuroscientist worth his or her Na⁺ knows that astrocytes commonly participate as a third member of a conventional “two-neurite” synapse.

I’m really excited by this work because it’s very likely that the electron microscopy data I commonly work with will hold the answer to this question: If gliotransmission takes the form of neurotransmitter vesicle-release, then looking at nanometer-resolution should be a good way to find it.