In vivo two‐photon uncaging of glutamate revealing the structure–function relationships of dendritic spines in the neocortex of adult mice

Non-technical summary  Neurons communicate with each other with synapses using chemical messengers. The major synapses in the cerebral cortex utilize glutamate as a messenger and are made on special submicron structures, called dendritic spines. Dendritic spines are diverse in their size and densely packed in the cortex. Therefore, an optical technique for application of glutamate to single spines (two-photon (TP) uncaging) has been intensively used to clarify their functions in vitro. We have here extended 2P uncaging to living adult brain, and found that spine sizes display tight correlations with their functions, such as rapid glutamate sensing and an increase in cytosolic Ca2+ concentrations, even in vivo, as they were reported for in vitro preparations. Our data suggest that the structure and motility of dendritic spines play a key role in the adult brain function.