Regulation of NMDAR-induced Microglia-Neuron Physical Interactions by the GluN2A Subunit. (a) Representative z-stack two-photon images of GFP-expressing microglia in hippocampal CA1 of acute brain slices before (left) and after 15 min of NMDA (30 µM) treatment (center) in the presence of GluN2A antagonist (top) or GluN2B antagonist (bottom). Rightmost images are merged images of the before (red) and after (green) images. Extending microglial processes can be visualized in the stratum pyramidale layer (dashed lines) in green. (b) Quantitative summary of corresponding data to (a); insert: high magnification image collected from a double trangenic mouse brain slices following NMDA-treatment. The images show microglial processes (GFP-labelled) making bulbous tipped contact (white arrows) with a neuron (YFP-labelled) following NMDA treatment. (c–f) Representative image of the field of view with boxed region that is expanded to show timelapse images of converging microglial processes (green) that terminate on a neuronal dendrite (white arrow) that occurs after NMDAR activation. (g,h) A schematic of sites of microglial process convergence events during a 30 minute imaging period from three representative experiments (g) and quantified summary (h) showing significantly reduced events with NVP but not Ifen during NMDA treatment. All data are presented as mean ± S.E.M. n = 4–6 slices each. ***P < 0.001.