Application of Thy1-mitoDsRed tg mice in studies of kainic acid (KA) excitotoxicity-induced mitochondrial fission in spinal cord motor neurons. A. Mice with phosphate-buffered saline (PBS) injections placed stereotaxically in lumbar spinal cord had motor neurons with perikaryal (asterisk identifies the nucleus of individual neurons in all images in A-C) DsRed-tagged mitochondria having normal mostly uniform appearances and distributions. B. Mice with KA injections in lumbar spinal cord and 12-hour recovery had motor neurons with perikaryal DsRed-tagged mitochondria appearing heterogeneous in size with an apparent increase in small round mitochondria. C. Mice with KA injections in lumbar spinal cord and 24-hour recovery had motor neurons with perikaryal DsRed-tagged mitochondria appearing as swollen, clumped or aggregated. Scale bar (in A) = 5 μm (same for B and C). Images are representative of four different tg mice per group. D. Western blot for Drp1 in lumbar spinal cord extracts of Thy1-mitoDsRed tg mice after intraspinal injection of PBS or KA and survival for 12 or 24 hours. Actin is shown for protein loading.