I’m reviewing a manuscript right now, and I always find it interesting that many neuroscientists seem to forget that the presence of small molecules like glutamate do not exclusively represent, neurotransmitters. Glutamate, like other amino acids that also happen to be neurotransmitters, are common carbon skeletons used in the metabolism of other molecules and in the assembly and disassembly of proteins in organisms as diverse as single celled organisms, up through plants and then multi-cellular animals.
This image above for instance, is a cross section of a grape vine tendril, probed for glutamate content. Interesting, no?