Effect of excitatory neurotransmitters on the motility of microglia in spinal dorsal horn. (A-E). Local application of 1 mM glutamate (Glu), AMPA, NMDA, glutamate uptake inhibitor dihydrokainate (DHK) or substance P (SP) cannot increase the motility of microglia. Dotted circle indicates the center of the drug application area. Microglial motility was imaged every 2 min for 30 min. The first image (0 min, left) and last image (30 min, middle) were shown here. To observe clearer motility, the 2 images were merged (right) and set as green and red for 0 and 30 min, respectively. Therefore the green reflects retracted portions, and the red reflects extended portions, whereas the yellow reflects unaltered portions. Bars equal to 20 μm.