This work was supported by the National Institutes of Health [Grant no. R01NS069726] and the American Heart Association Grant in Aid Grant [Grant no. 13GRNT17020004] to SD.

Note: Mice (C57BL/6J, male) aged 10 &#8211; 12 weeks were used in this study. All the procedures were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals and were approved by the University of Missouri Institutional Animal Care and Use Committee (IACUC).&#160;
1. Pre-Surgery
<ol>
	<li>The day before surgery autoclave and sterilize all the surgical instruments. Wrap the instruments and autoclave at 121 oC at 15 psi for 30 min followed by 30 min of drying (121 oC, 15 psi, 30/30 cycle). Place the instruments in a clean and sterile environment until further use.</li>
	<li>Prepare fresh Rose Bengal (RB) solution (20 mg/ml in sterile saline) every time before the surgery. To completely dissolve RB, vortex the tube then followed by sonication for 5 min at 50/60 Hz with output power of 19 W. Wrap the tube in aluminum foil and protect it from light until further used during surgery.</li>
	<li>Prepare a mixture of ketamine/xylazine in sterile saline. Add 125 &#181;l of xylazine (stock concentration: 20 mg/ml) and 325 &#181;l of ketmaine (stock concentration: 100 mg/ml) and 550 &#181;l of sterile saline to make a final volume of 1 ml of anesthetic mixture.</li>
	<li>Pre-warm the homeothermic heating pad.</li>
	<li>Pre-warm the metal halide lamp (light source for FN1 epi-fluorescence microscope) for 30 min to stabilize the lamp power.</li>
	<li>Adjust the size of the illuminated region to a diameter of 1 mm using 10X objective and a reticle by adjusting the field diaphragm in the upright FN1 epi-fluorescence microscope.</li>
</ol>
2. Surgical Procedure
<ol>
	<li>Anesthetize the mouse with a dose of ketamine (130 mg/kg B. wt.) and xylazine (10 mg/kg B. wt.). Based on the cocktail in 1.3,&#160; 4 &#181;l per g of mouse B. wt. are needed. Sterilize the site of injection with an alcohol swab and administer the anesthetics through the intra-peritoneal (IP) route. Take care not to inject the anesthetics into the blood vessels or muscle as this would delay the induction and recovery of the animal.</li>
	<li>Apply artificial tear ointment to both eyes of the mouse to prevent drying and place the animal on the heating pad to prevent hypothermia.</li>
	<li>Preparation of animal
	<ol>
		<li>Check the animal for proper surgical level anesthesia by using the toe pinch response.</li>
		<li>Once the animal has reached surgical level of anesthesia, clip the hair on the dorsal surface around midline of the animal using an electric hair trimmer. Scrub the surgical site with 70% ethanol followed by betadine solution three times. Cover the site with a sterile surgical drape until next step.</li>
	</ol>
	</li>
	<li>Surgical procedure to thin the bone to expose the spinal cord
	<ol>
		<li>Place the mouse in a prone position over the homeothermic heating pad on the surgical platform (Figure 1A). Properly secure the mouse posture using a snout clamp to maintain an elongated neck region (Figure 1A, B).</li>
		<li>Make an incision (approximately 1 cm long) using surgical scissors along the dorsal mid line extending from the thoracic vertebrae T9 to T12. Move aside the skin to expose surgical area.</li>
		<li>Using a scalpel, carefully clear the muscle to expose the dorsal spines at T9 - T12 vertebrae. Stop bleeding in each step by applying gentle pressure with sterile cotton swab. Separate T10 - T12 vertebrae from the surrounding muscle and secure them using a vertebral clamp to stabilize and prevent any movement (Figure 1A, B).</li>
		<li>Using a high speed drill with bone polishing drill bit, carefully and gently thin the dorsal surface of T10 or T11 vertebra to visualize the posterior spinal vein and other small vessels on the dorsal surface of the SC (Figure 1C).</li>
		<li>To prevent thermal damage due to heat generated during the thinning procedure, apply a gentle and constant stream of normal saline along with constant suction to remove the debris.</li>
		<li>Using a scalpel carefully smooth the bone surface until the main vessel is clearly visible. Take care not to damage the spinal cord during this process.</li>
		<li>Once the blood vessel is visualized, administer RB at a dose of 30 mg/kg (body weight) through retro-orbital sinus route using an insulin syringe.</li>
		<li>Measure blood flow using a Laser Doppler flowmeter after 3 min following RB injection if necessary (Figure 2A, B). Maintain asepsis during entire procedure.</li>
	</ol>
	</li>
</ol>
3. Induction of PT
<ol>
	<li>Place the animal on an X-Y position adjustable stage over a Lab-Jack which can adjust the height. Adjust the position of the mouse so the exposed region of T11 spinal cord is directly under the 10x objective of the FN1 epi-fluorescence microscope (Figure 3A).</li>
	<li>Set the power of the light source at 12% and irradiate the T11 region with a diameter of 0.75 mm in the middle of thinned spinal cord (Note: this region includes the posterior spinal vein and other capillaries) with a green light (wavelength 540 - 580 nm, which is achieved by the filter cube in the microscope) through the 10X objective for 2 min. Take images at the beginning and end of irradiation (Figure 3B, C) and record the time of the experiment at this point.</li>
	<li>Measure blood flow again for 10 min if necessary by placing the laser Doppler probe to the same position above the spinal cord as in 2.4.8 (Figure 2A, B).</li>
	<li>After irradiation check for any hemorrhage and if none found proceed to suturing the animal. Suture the superficial fascia along with the muscles on the either side of spinal cord using an absorbable suture or&#160;4-0 size silk&#160;suture. Take care not to damage the exposed SC. Suture the skin with 4-0 silk suture. Apply Betadine or iodine to the edges of the skin after suturing.</li>
</ol>
4. Post-surgery Care
<ol>
	<li>After suturing, place the animal on the heating pad for recovery. After recovery check the animals for signs of neurological deficits by observing the movement of both hind-limbs. Do not leave the animal unattended until it has regained sufficient consciousness to maintain sternal recumbency.</li>
	<li>Transfer the animals to the home cage. Do not return the animal that has undergone surgery to the company of other animals until fully recovered.</li>
	<li>Check the animals at regular intervals. In case of severe neurological deficits, provide proper care like evacuation of bladder, administration of analgesics (buprenorphine, 0.05 - 0.1 mg/kg). Check for dehydration and administer normal saline subcutaneously in severe case.&#160;Usually, buprenorphine ( 0.1 mg/kg) will be administered after suturing to relieve pain in the surgical site.</li>
	<li>If animals are not immediately euthanized after surgery, we will put high water content diet on the cage floor, so the animals can reach the food easily.</li>
</ol>
5. Transcardial Perfusion, Nissl staining and Immunostaining
<ol>
	<li>Transcardially perfuse the animal as described previously17-20.
	<ol>
		<li>Anesthetize the animal as described earlier in the protocol and transcardially perfuse with phosphate buffer saline (PBS, pH 7.4), followed by ice-cold 4% paraformaldehyde (PFA) in PBS.</li>
		<li>After perfusion, remove the spinal cord (SC) and post-fix it in 4% PFA in PBS at 4 &#176;C O/N. Transfer the fixed SC into PBS with 30% sucrose and keep it for 2 - 3 days until it sinks to the bottom of the tube.</li>
		<li>Using a cryostat cut the spinal cord into 30 &#181;m thick sections and place them serially on a gelatin-coated glass slides or in a 48-well plate with 0.01 M PBS.</li>
	</ol>
	</li>
	<li>Nissl staining: To inspect the injury caused by PT perform a Nissl staining on spinal cord sections as previously described17-20.
	<ol>
		<li>Briefly, collect every fifth spinal cord slice on the glass slides and stain with 0.25% cresyl violet. Take images of the stained sections (Figure 4).</li>
	</ol>
	</li>
	<li>Immunostaining: As described previously using a floating section method17,18,20.
	<ol>
		<li>Briefly, stain the spinal cord sections by incubating O/N at 4 &#176;C with rabbit anti-glia fibrillary acidic protein (GFAP) polyclonal antibody (1:300), rabbit anti-NeuN antibody (1:300), and rabbit anti-Iba1 antibody (1:500) followed by donkey anti rabbit Alexa 568-conjugated IgG (1:400) secondary antibodies for 4 h at RT. Take images with a fluorescent microscope (Figure 5).</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Cadotte, D. W., Fehlings, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+cord+injury:+a+systematic+review+of+current+treatment+options.">Spinal cord injury: a systematic review of current treatment options.</a> Clin Orthop Relat Res. 469 (3), 732-741 (2011).</li><li>Cheriyan, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+cord+injury+models:+a+review.">Spinal cord injury models: a review.</a> Spinal Cord. 52 (8), 588-595 (2014).</li><li>Young, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secondary+injury+mechanisms+in+acute+spinal+cord+injury.">Secondary injury mechanisms in acute spinal cord injury.</a> J Emerg Med. 11, 13-22 (1993).</li><li>Crowe, M. J., Bresnahan, J. C., Shuman, S. L., Masters, J. N., Beattie, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis+and+delayed+degeneration+after+spinal+cord+injury+in+rats+and+monkeys.">Apoptosis and delayed degeneration after spinal cord injury in rats and monkeys.</a> Nat Med. 3 (1), 73-76 (1997).</li><li>Soubeyrand, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+norepinephrine+on+spinal+cord+blood+flow+and+parenchymal+hemorrhage+size+in+acute-phase+experimental+spinal+cord+injury.">Effect of norepinephrine on spinal cord blood flow and parenchymal hemorrhage size in acute-phase experimental spinal cord injury.</a> Eur Spine J. 23 (3), 658-665 (2014).</li><li>Soubeyrand, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+and+spatial+quantification+using+contrast-enhanced+ultrasonography+of+spinal+cord+perfusion+during+experimental+spinal+cord+injury.">Real-time and spatial quantification using contrast-enhanced ultrasonography of spinal cord perfusion during experimental spinal cord injury.</a> Spine (Phila Pa 1976). 37 (22), E1376-E1382 (2012).</li><li>Mautes, A. E., Weinzierl, M. R., Donovan, F., Noble, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+events+after+spinal+cord+injury:+contribution+to+secondary+pathogenesis).">Vascular events after spinal cord injury: contribution to secondary pathogenesis).</a> Phys Ther. 80 (7), 673-687 (2000).</li><li>Liu, X. Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+and+glial+apoptosis+after+traumatic+spinal+cord+injury.">Neuronal and glial apoptosis after traumatic spinal cord injury.</a> J Neurosci. 17 (14), 5395-5406 (1997).</li><li>Liu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+experimental+study+of+cell+apoptosis+and+correlative+gene+expression+after+tractive+spinal+cord+injury+in+rats.">An experimental study of cell apoptosis and correlative gene expression after tractive spinal cord injury in rats.</a> Zhonghua Wai Ke Za Zhi. 42 (23), 1434-1437 (2004).</li><li>Hirose, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activated+protein+C+reduces+the+ischemia/reperfusion-induced+spinal+cord+injury+in+rats+by+inhibiting+neutrophil+activation.">Activated protein C reduces the ischemia/reperfusion-induced spinal cord injury in rats by inhibiting neutrophil activation.</a> Ann Surg. 232 (2), 272-280 (2000).</li><li>Oyinbo, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secondary+injury+mechanisms+in+traumatic+spinal+cord+injury:+a+nugget+of+this+multiply+cascade.">Secondary injury mechanisms in traumatic spinal cord injury: a nugget of this multiply cascade.</a> Acta Neurobiol Exp (Wars). 71 (2), 281-299 (2011).</li><li>Guerit, J. M., Dion, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=State-of-the-art+of+neuromonitoring+for+prevention+of+immediate+and+delayed+paraplegia+in+thoracic+and+thoracoabdominal+aorta+surgery).">State-of-the-art of neuromonitoring for prevention of immediate and delayed paraplegia in thoracic and thoracoabdominal aorta surgery).</a> Ann Thorac Surg. 74 (5), S1867-S1869 (2002).</li><li>Schepens, M. A., Heijmen, R. H., Ranschaert, W., Sonker, U., Morshuis, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thoracoabdominal+aortic+aneurysm+repair:+results+of+conventional+open+surgery.">Thoracoabdominal aortic aneurysm repair: results of conventional open surgery.</a> Eur J Vasc Endovasc Surg. 37 (6), 640-645 (2009).</li><li>Braeuninger, S., Kleinschnitz, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rodent+models+of+focal+cerebral+ischemia:+procedural+pitfalls+and+translational+problems.">Rodent models of focal cerebral ischemia: procedural pitfalls and translational problems.</a> Exp Transl Stroke Med. 1, 8 (2009).</li><li>Carmichael, S. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rodent+models+of+focal+stroke:+size,+mechanism,+and+purpose.">Rodent models of focal stroke: size, mechanism, and purpose.</a> NeuroRx. 2 (3), 396-409 (2005).</li><li>Dietrich, W. D., Ginsberg, M. D., Busto, R., Watson, B. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemically+induced+cortical+infarction+in+the+rat.+1.+Time+course+of+hemodynamic+consequences.">Photochemically induced cortical infarction in the rat. 1. Time course of hemodynamic consequences.</a> J Cereb Blood Flow Metab. 6 (2), 184-194 (1986).</li><li>Zhang, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+protective+role+of+PBEF+in+a+mouse+model+of+cerebral+ischemia.">Neuronal protective role of PBEF in a mouse model of cerebral ischemia.</a> J Cereb Blood Flow Metab. 30 (12), 1962-1971 (2010).</li><li>Li, H., Zhang, N., Sun, G., Ding, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+the+group+I+mGluRs+reduces+acute+brain+damage+and+improves+long-term+histological+outcomes+after+photothrombosis-induced+ischaemia.">Inhibition of the group I mGluRs reduces acute brain damage and improves long-term histological outcomes after photothrombosis-induced ischaemia.</a> ASN Neuro. 5 (3), 195-207 (2013).</li><li>Li, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Histological,+cellular+and+behavioral+assessments+of+stroke+outcomes+after+photothrombosis-induced+ischemia+in+adult+mice.">Histological, cellular and behavioral assessments of stroke outcomes after photothrombosis-induced ischemia in adult mice.</a> BMC Neurosci. 15, 58 (2014).</li><li>Wang, T., Cui, W., Xie, Y., Zhang, W., Ding, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlling+the+Volume+of+the+Focal+Cerebral+Ischemic+Lesion+through+Photothrombosis.">Controlling the Volume of the Focal Cerebral Ischemic Lesion through Photothrombosis.</a> American Journal of Biomedical Sciences. 2 (1), 33-42 (2010).</li><li>Schroeter, M., Jander, S., Stoll, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-invasive+induction+of+focal+cerebral+ischemia+in+mice+by+photothrombosis+of+cortical+microvessels:+characterization+of+inflammatory+responses.">Non-invasive induction of focal cerebral ischemia in mice by photothrombosis of cortical microvessels: characterization of inflammatory responses.</a> J Neurosci Methods. 117 (1), 43-49 (2002).</li><li>Boquillon, M., Boquillon, J. P., Bralet, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemically+induced,+graded+cerebral+infarction+in+the+mouse+by+laser+irradiation+evolution+of+brain+edema.">Photochemically induced, graded cerebral infarction in the mouse by laser irradiation evolution of brain edema.</a> J Pharmacol Toxicol Methods. 27 (1), 1-6 (1992).</li><li>Kim, G. W., Lewen, A., Copin, J., Watson, B. D., Chan, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+cytosolic+antioxidant,+copper/zinc+superoxide+dismutase,+attenuates+blood-brain+barrier+disruption+and+oxidative+cellular+injury+after+photothrombotic+cortical+ischemia+in+mice.">The cytosolic antioxidant, copper/zinc superoxide dismutase, attenuates blood-brain barrier disruption and oxidative cellular injury after photothrombotic cortical ischemia in mice.</a> Neuroscience. 105 (4), 1007-1018 (2001).</li><li>Schmidt, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photochemically+induced+ischemic+stroke+in+rats.">Photochemically induced ischemic stroke in rats.</a> Exp Transl Stroke Med. 4 (1), 13 (2012).</li><li>Lang-Lazdunski, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spinal+cord+ischemia.+Development+of+a+model+in+the+mouse.">Spinal cord ischemia. Development of a model in the mouse.</a> Stroke. 31 (1), 208-213 (2000).</li><li>Wang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+simplified+spinal+cord+ischemia+model+in+mice.">Development of a simplified spinal cord ischemia model in mice.</a> J Neurosci Methods. 189 (2), 246-251 (2010).</li><li>Labat-gest, V., Tomasi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photothrombotic+ischemia:+a+minimally+invasive+and+reproducible+photochemical+cortical+lesion+model+for+mouse+stroke+studies.">Photothrombotic ischemia: a minimally invasive and reproducible photochemical cortical lesion model for mouse stroke studies.</a> J Vis Exp. (76), (2013).</li><li>Lu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+and+imaging+of+photothrombotic+stroke+in+conscious+and+freely+moving+rats.">Induction and imaging of photothrombotic stroke in conscious and freely moving rats.</a> J Biomed Opt. 19 (9), 96013 (2014).</li><li>Seto, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Induction+of+ischemic+stroke+in+awake+freely+moving+mice+reveals+that+isoflurane+anesthesia+can+mask+the+benefits+of+a+neuroprotection+therapy.">Induction of ischemic stroke in awake freely moving mice reveals that isoflurane anesthesia can mask the benefits of a neuroprotection therapy.</a> Front Neuroenergetics. 6 (1), (2014).</li><li>Bell, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toll-like+receptor+4-dependent+microglial+activation+mediates+spinal+cord+ischemia-reperfusion+injury.">Toll-like receptor 4-dependent microglial activation mediates spinal cord ischemia-reperfusion injury.</a> Circulation. 128 (11 Suppl 1), S152-S156 (2013).</li><li>Smith, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+evolution+of+chemokine+release+supports+a+bimodal+mechanism+of+spinal+cord+ischemia+and+reperfusion+injury.">The evolution of chemokine release supports a bimodal mechanism of spinal cord ischemia and reperfusion injury.</a> Circulation. 126 (11 Suppl 1), S110-S117 (2012).</li><li>Jia, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+stress+in+spinal+cord+injury+and+antioxidant-based+intervention.">Oxidative stress in spinal cord injury and antioxidant-based intervention.</a> Spinal Cord. 50 (4), 264-274 (2012).</li></ol>

The authors have nothing to disclose.

In this study, we described a photothrombotic model of SC ischemia. Due to advances in genetic engineering there has been a surge in commercially available transgenic mice which has made it possible to study the impact of specific genes involved in the ischemic pathophysiology in the SC. The aim of the study was to develop a reproducible mouse model of spinal cord ischemia. Here we adapted a cortical PT model to induce SCI in mice. Following surgery the posterior spinal vein and capillaries on the dorsal...

Traumatic spinal cord injury (SCI) is a devastating clinical condition affecting the sensorimotor and autonomic functions of the SC. Patients surviving SCI are often left with debilitating paraplegia that significantly affects their daily activities and quality of life1. Experimental SCI models have been an indispensable tool in the scientific investigation to understand the pathophysiology of SCI and associated neural repair processes. These models have also been used to test the preclinical efficacy of various experimental neuroprotective interventions that are aimed at functional recovery. Currently, majority of the SCI models in practice employ the use of physical blunt force to mechanically disrupt and injure the SC. These methods include contusion, compression, dislocation and transection of the SC2. It has been suggested that after the primary mechanical insult a secondary injury in the form of ischemia sets in in the injured SC3,4. The etiology of secondary ischemia includes extensive tissue degeneration, parenchymal hemorrhage and sometimes by obstruction of blood vessels by tissue edema5-7. As a result of the secondary injury the integrity of SC is further affected, neurons and glial cells are severely impaired in function and viability and undergo apoptosis which leads to infarct growth during the chronic stage of injury, analogous to the growth of ischemic penumbra following stroke8,9. Several mechanisms like excitotoxicity, free radical production, and inflammation have been reported to be responsible for the ischemic cell death following SCI10,11. In addition, SC ischemia is a serious complication of thoraco-abdominal aortic aneurysm repair surgeries which often lead to paraplegia in the patients12,13. In spite of such high clinical impact very few models of spinal cord ischemia with high reproducibility are currently available.
Photothrombosis (PT) is a commonly used method for the induction of focal ischemia in the brain14-20. The technique is fairly non-invasive, highly reproducible and produces a precise focal ischemic lesion in the exposed area of the brain17-21. This is achieved by systemic administration of photoactive dyes like Rose Bengal (RB)16-20,22 or erythrosine B23 followed by localized irradiation of blood vessels with proper light source. Photoactivation of the dye causes the generation of free radicals which disrupt the integrity of the smooth vascular endothelium, and cause the platelets to accumulate, which subsequently forms a thrombus. The obstruction of blood flow by the thrombus results in an infarct in the region supplied by the vessel24. Due to ease of control on the intensity and duration of irradiation this procedure yields a highly uniform and reproducible infarct. Furthermore, this method can be employed to induce an infarct at various anatomical locations enabling spatial (e.g., grey matter vs. white matter) understanding of the effect of ischemia.
The aim of the current study is to develop an easy and highly reproducible model of SC ischemia in mice. We described the procedure of a PT model of SC ischemia in mice. Results from histology and immunostaining demonstrated that PT can effectively induce SC infarction, neuronal loss and reactive gliosis.

<table border="0" cellpadding="0" cellspacing="0" width="1050">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">&#160;Rose Bengal</td>
			<td style="width:233px;">Sigma-Aldrich</td>
			<td style="width:180px;">330000</td>
			<td style="width:421px;">20 mg/ml in sterile saline</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">C57Bl6/J</td>
			<td>Jackson lab</td>
			<td>664</td>
			<td>22-25g</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ketamine&#160;</td>
			<td>VEDCO</td>
			<td>NDC-50989-996-06</td>
			<td>100 mg/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Xylazine&#160;</td>
			<td>VEDCO</td>
			<td>NDC-50989-234-11</td>
			<td>100 mg/ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Betadine solution</td>
			<td>Purdue</td>
			<td>NDC-67618-150-01</td>
			<td>10% povidone iodine topical solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Normal saline</td>
			<td>Abott Laboratories</td>
			<td>04930-04-10</td>
			<td>For diluting RB, anaesthesia and for preventing tissue from drying</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Artificial tears ointment&#160;</td>
			<td>Rugby</td>
			<td>NDC-0536-6550-91</td>
			<td>83% white petrolatum</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>Decon labs.Inc</td>
			<td>2716</td>
			<td>70% ethanol for disinfection</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Metal halide lamp</td>
			<td>EXFO, Canada</td>
			<td>X-Cite 120 PC&#160;</td>
			<td>Set power at 12%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Spring scissors&#160;</td>
			<td>Fine Science Tool</td>
			<td>15000-10</td>
			<td>for minor dissection</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scissors (angled to side)</td>
			<td>Fine Science Tool</td>
			<td>14063-011</td>
			<td>No. 3 handle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Standard scalpel</td>
			<td>Fine Science Tool</td>
			<td>10003-12</td>
			<td>for removing muscle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scalpel blade</td>
			<td>Feather</td>
			<td>2976</td>
			<td>No. 10</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Forceps (curved)</td>
			<td>Fine Science Tool</td>
			<td>11150-10</td>
			<td>for holding tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Forceps (straight)</td>
			<td>Fine Science Tool</td>
			<td>11151-10</td>
			<td>for holding tissue</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Needle holder&#160;</td>
			<td>Fine Science Tool</td>
			<td>12002-12</td>
			<td>for suturing</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tissue adhesive glue</td>
			<td>3M Vetbond</td>
			<td>1469SB</td>
			<td>to adhere to edges of the cut skin</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Monofilament polypropylene&#160;</td>
			<td>USSC Sutures</td>
			<td>VP-521</td>
			<td>Size = 4-0 (for fascia)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Perma-hand silk</td>
			<td>Ethicon</td>
			<td>683G</td>
			<td>Size = 4-0 (for skin)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micro drill</td>
			<td>Roboz Surgical Instrument Co. Inc.</td>
			<td>RS-6300</td>
			<td>with bone polishing drill bit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Laser doppler flowmeter</td>
			<td>Moor Instruments</td>
			<td>moorVMS-LDF1</td>
			<td>for monitoring change in blood flow</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Heating pad</td>
			<td>Fine Science Tool</td>
			<td>21052-00</td>
			<td>to prevent hypothermia</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Lab-Jack</td>
			<td>Fisher scientific&#160;</td>
			<td>14-673-50</td>
			<td>4x4 in plate to adjust the height of the animal</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">X-Y gliding stage&#160;</td>
			<td>Amscope</td>
			<td>GT100</td>
			<td>for positioning the animal under microscope&#160;&#160;</td>
		</tr>
	</tbody>
</table>

photothrombosis-induced focal ischemia as a model of spinal cord injury in mice

Spinal cord injury (SCI) is a devastating clinical condition causing permanent changes in sensorimotor and autonomic functions of the spinal cord (SC) below the site of injury. The secondary ischemia that develops following the initial mechanical insult is a serious complication of the SCI and severely impairs the function and viability of surviving neuronal and non-neuronal cells in the SC. In addition, ischemia is also responsible for the growth of lesion during chronic phase of injury and interferes with the cellular repair and healing processes. Thus there is a need to develop a spinal cord ischemia model for studying the mechanisms of ischemia-induced pathology. Focal ischemia induced by photothrombosis (PT) is a minimally invasive and very well established procedure used to investigate the pathology of ischemia-induced cell death in the brain. Here, we describe the use of PT to induce an ischemic lesion in the spinal cord of mice. Following retro-orbital sinus injection of Rose Bengal, the posterior spinal vein and other capillaries on the dorsal surface of SC were irradiated with a green light resulting in the formation of a thrombus and thus ischemia in the affected region. Results from histology and immunochemistry studies show that PT-induced ischemia caused spinal cord infarction, loss of neurons and reactive gliosis. Using this technique a highly reproducible and relatively easy model of SCI in mice can be achieved that would serve the purpose of scientific investigations into the mechanisms of ischemia induced cell death as well as the efficacy of neuroprotective drugs. This model will also allow exploration of the pathological changes that occur following SCI in live mice like axonal degeneration and regeneration, neuronal and astrocytic Ca2+ signaling using two-photon microscopy.

The aim of this study was to produce spinal cord ischemia in mice using a PT model. After the desired region of bone above the spinal cord (T10 - T12) was thinned, Rose Bengal was injected through retro-orbital sinus route, and ischemia was induced by PT. Figure 1A, B show the mouse positioned in a custom-made surgical platform during surgery. The mouse was held in place by a snout clamp and two adjustable vertebrate clamps to stabilize the spinal cord. Figure 1C show a thinned window ab...

Watch this Scientific Journal Video about Photothrombosis-induced Focal Ischemia as a Model of Spinal Cord Injury in Mice at JoVE.com

Photothrombosis-induced Focal Ischemia as a Model of Spinal Cord Injury in Mice

Photothrombosis is a minimally invasive and highly reproducible procedure to induce focal ischemia in the spinal cord and serves as a model of spinal cord injury in mice.

Spinal cord injury (SCI) is a devastating clinical condition causing permanent changes in sensorimotor and autonomic functions of the spinal cord (SC) ...

photothrombosis-induced-focal-ischemia-as-model-spinal-cord-injury

Research

JoVE Journal

Medicine

13.2K Views.  University of Missouri. Photothrombosis is a minimally invasive and highly reproducible procedure to induce focal ischemia in the spinal cord and serves as a model of spinal cord injury in mice. 

Video: Photothrombosis-induced Focal Ischemia as a Model of Spinal Cord Injury in Mice

Acute and Chronic Tactile Sensory Testing after Spinal Cord Injury in Rats

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory testing in rat SCI models is needed. However, until recently, no single testing approach had been validated for SCI so that standardized methods have not been implemented across labs. Additionally, available testing methods could not be implemented acutely or when severe motor impairments existed, preventing studies of the development of SCI-induced allodynia3. Here we present two validated sensory testing methods using von Frey Hair (VFH) monofilaments which quantify changes in tactile sensory thresholds after SCI4-5. One test is the well-established Up-Down test which demonstrates high sensitivity and specificity across different SCI severities when tested chronically5. The other test is a newly-developed dorsal VFH test that can be applied acutely after SCI when allodynia develops, prior to motor recovery4-5. Each VFH monofilament applies a calibrated force when touched to the skin of the hind paw until it bends. In the up-down method, alternating VFHs of higher or lower forces are used on the plantar L5 dermatome to delineate flexor withdrawal thresholds. Successively higher forces are applied until withdrawal occurs then lower force VFHs are used until withdrawal ceases. The tactile threshold reflects the force required to elicit withdrawal in 50% of the stimuli. For the new test, each VFH is applied to the dorsal L5 dermatome of the paw while the rat is supported by the examiner. The VFH stimulation occurs in ascending order of force until at least 2 of 3 applications at a given force produces paw withdrawal. Tactile sensory threshold is the lowest force to elicit withdrawal 66% of the time. Acclimation, testing and scoring procedures are described. Aberrant trials that require a retest and typical trials are defined. Animal use was approved by Ohio State University Animal Care and Use Committee.

We describe two tactile sensory testing methods for acute or chronic periods of spinal cord injury in rats. These validated procedures can detect the development and maintenance of allodynia-like sensations.

Spinal cord injury (SCI) impairs sensory systems causing allodynia1-8. To identify cellular and molecular causes of allodynia, sensitive and valid sensory ...

Controlled Cervical Laceration Injury in Mice

Use of genetically modified mice enhances our understanding of molecular mechanisms underlying several neurological disorders such as a spinal cord injury (SCI). Freehand manual control used to produce a laceration model of SCI creates inconsistent injuries often associated with a crush or contusion component and, therefore, a novel technique was developed. Our model of cervical laceration SCI has resolved inherent difficulties with the freehand method by incorporating 1) cervical vertebral stabilization by vertebral facet fixation, 2) enhanced spinal cord exposure, and 3) creation of a reproducible laceration of the spinal cord using an oscillating blade with an accuracy of &plusmn;0.01 mm in depth without associated contusion. Compared to the standard methods of creating a SCI laceration such as freehand use of a scalpel or scissors, our method has produced a consistent lesion. This method is useful for studies on axonal regeneration of corticospinal, rubrospinal, and dorsal ascending tracts.

A novel technique to create a reproducible in vivo model of cervical spinal cord laceration injury in the mouse is described. This technique is based on spine stabilization by fixation of the cervical facets and laceration of the spinal cord using an oscillating blade with an accuracy of &plusmn;0.01 mm.

Use of genetically modified mice enhances our  understanding of molecular mechanisms underlying several neurological disorders  such as a spinal cord ...

A Contusion Model of Severe Spinal Cord Injury in Rats

The translational potential of novel treatments should be investigated in severe spinal cord injury (SCI) contusion models. A detailed methodology is described to obtain a consistent model of severe SCI. Use of a stereotactic frame and computer controlled impactor allows for creation of reproducible injury. Hypothermia and urinary tract infection pose significant challenges in the post-operative period. Careful monitoring of animals with daily weight recording and bladder expression allows for early detection of post-operative complications. The functional results of this contusion model are equivalent to transection models. The contusion model can be utilized to evaluate the efficacy of both neuroprotective and neuroregenerative approaches.

A contusion model of severe spinal cord injury is described. Detailed pre-operative, operative and post-operative steps are described to obtain a consistent model.

The translational potential of novel treatments should be investigated in severe spinal cord injury (SCI) contusion models. A detailed methodology is ...

Ischemia-reperfusion Model of Acute Kidney Injury and Post Injury Fibrosis in Mice

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often unreported mortality rates that may confound analyses. Bilateral renal pedicle clamping is commonly used to induce IR-AKI, but differences between effective clamp pressures and/or renal responses to ischemia between kidneys often lead to more variable results. In addition, shorter clamp times are known to induce more variable tubular injury, and while mice undergoing bilateral injury with longer clamp times develop more consistent tubular injury, they often die within the first 3 days after injury due to severe renal insufficiency. To improve post-injury survival and obtain more consistent and predictable results, we have developed two models of unilateral ischemia-reperfusion injury followed by contralateral nephrectomy. Both surgeries are performed using a dorsal approach, reducing surgical stress resulting from ventral laparotomy, commonly used for mouse IR-AKI surgeries. For induction of moderate injury BALB/c mice undergo unilateral clamping of the renal pedicle for 26 min and also undergo simultaneous contralateral nephrectomy. Using this approach, 50-60% of mice develop moderate AKI 24 hr after injury but 90-100% of mice survive. To induce more severe AKI, BALB/c mice undergo renal pedicle clamping for 30 min followed by contralateral nephrectomy 8 days after injury. This allows functional assessment of renal recovery after injury with 90-100% survival. Early post-injury tubular damage as well as post injury fibrosis are highly consistent using this model.

We describe models of moderate and severe ischemia-reperfusion-induced kidney injury in which the mice undergo unilateral renal pedicle clamping followed by simultaneous or delayed contralateral nephrectomy, respectively. These models consistently give rise to renal dysfunction and post-injury fibrosis, but injury severity and survival are dependent on mouse background, age and surgical equipment.

Ischemia-reperfusion induced acute kidney injury (IR-AKI) is widely used as a model of AKI in mice, but results are often quite variable with high, often ...

Reproducable Paraplegia by Thoracic Aortic Occlusion in a Murine Model of Spinal Cord Ischemia-reperfusion

Background 
Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered advancements to decrease the occurrence this injury.&#160;The current model demonstrates reproducible lower&#160;extremity paralysis following thoracic aortic occlusion.
Methods 
Adult male C57BL6 mice were anesthetized with isoflurane. Through a cervicosternal incision the aorta was exposed. The descending thoracic aorta and left subclavian arteries were identified without entrance into pleural space. Skeletonization of these arteries was followed by immediate closure (Sham) or occlusion for 4 min (moderate ischemia) or 8 min (prolonged ischemia). The sternotomy and skin were closed and the mouse was transferred to warming bed for recovery.&#160; Following recovery, functional analysis was obtained at 12 hr intervals until 48 hr.
Results 
Mice that underwent sham surgery showed no observable hind&#160;limb deficit. Mice subjected to moderate ischemia for 4 min had minimal functional deficit at 12 hr followed by progression to complete paralysis at 48 hr. Mice subjected to prolonged ischemia had an immediate paralysis with no observable hind-limb movement at any point in the postoperative period. There was no observed intraoperative or post&#160;operative mortality.
Conclusion 
Reproducible lower extremity paralysis whether immediate or delayed can be achieved in a murine model. Additionally, by using a median sternotomy and careful dissection, high survival rates, and reproducibility can be achieved.

The lack of mechanistic understanding of spinal cord ischemia-reperfusion injury has hindered further adjuncts to prevent paraplegia following high risk aortic operations. Thus, the development of animal models is imperative. This manuscript demonstrates reproducible lower extremity paralysis following thoracic aortic occlusion in a murine model.

Background
Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered ...

Controlled Cortical Impact Model for Traumatic Brain Injury

Every year over a million Americans suffer a traumatic brain injury (TBI). Combined with the incidence of TBIs worldwide, the physical, emotional, social, and economical effects are staggering. Therefore, further research into the effects of TBI and effective treatments is necessary. The controlled cortical impact (CCI) model induces traumatic brain injuries ranging from mild to severe. This method uses a rigid impactor to deliver mechanical energy to an intact dura exposed following a craniectomy. Impact is made under precise parameters at a set velocity to achieve a pre-determined deformation depth. Although other TBI models, such as weight drop and fluid percussion, exist, CCI is more accurate, easier to control, and most importantly, produces traumatic brain injuries similar to those seen in humans. However, no TBI model is currently able to reproduce pathological changes identical to those seen in human patients. The CCI model allows investigation into the short-term and long-term effects of TBI, such as neuronal death, memory deficits, and cerebral edema, as well as potential therapeutic treatments for TBI.

Traumatic brain injuries (TBIs) remain a serious health problem. Using the controlled cortical impact surgery model, research on the effects of TBI and possible treatment methods may be performed.

Every year over a million Americans suffer a traumatic brain injury (TBI).  Combined with the incidence of TBIs worldwide, the physical, emotional, ...

A Radio-telemetric System to Monitor Cardiovascular Function in Rats with Spinal Cord Transection and Embryonic Neural Stem Cell Grafts

High thoracic or cervical spinal cord injury (SCI) can lead to cardiovascular dysfunction. To monitor cardiovascular parameters, we implanted a catheter connected to a radio transmitter into the femoral artery of rats that underwent a T4 spinal cord transection with or without grafting of embryonic brainstem-derived neural stem cells expressing green fluorescent protein. Compared to other methods such as cannula insertion or tail-cuff, telemetry is advantageous to continuously monitor blood pressure and heart rate in freely moving animals. It is also capable of long term multiple data acquisitions. In spinal cord injured rats, basal cardiovascular data under unrestrained condition and autonomic dysreflexia in response to colorectal distension were successfully recorded. In addition, cardiovascular parameters before and after SCI can be compared in the same rat if a transmitter is implanted before a spinal cord transection. One limitation of the described telemetry procedure is that implantation in the femoral artery may influence the blood supply to the ipsilateral hindlimb.

We present a protocol for using a radio-telemetric system to record cardiovascular parameters in T4 spinal cord transected rats eight weeks after embryonic brainstem neural stem cell grafting into the lesion site. Telemetry is an advanced technique to accurately evaluate cardiovascular function in conscious freely moving spinal cord injured rats.

High thoracic or cervical spinal cord injury (SCI) can lead to cardiovascular dysfunction. To monitor cardiovascular parameters, we implanted a catheter ...

Neural Stem Cell Transplantation in Experimental Contusive Model of Spinal Cord Injury

Spinal cord injury is a devastating clinical condition, characterized by a complex of neurological dysfunctions. Animal models of spinal cord injury can be used both to investigate the biological responses to injury and to test potential therapies. Contusion or compression injury delivered to the surgically exposed spinal cord are the most widely used models of the pathology. In this report the experimental contusion is performed by using the Infinite Horizon (IH) Impactor device, which allows the creation of a reproducible injury animal model through definition of specific injury parameters. Stem cell transplantation is commonly considered a potentially useful strategy for curing this debilitating condition. Numerous studies have evaluated the effects of transplanting a variety of stem cells. Here we demonstrate an adapted method for spinal cord injury followed by tail vein injection of cells in CD1 mice. In short, we provide procedures for: i) cell labeling with a vital tracer, ii) pre-operative care of mice, iii) execution of a contusive spinal cord injury, and iv) intravenous administration of post mortem neural precursors. This contusion model can be utilized to evaluate the efficacy and safety of stem cell transplantation in a regenerative medicine approach.

Spinal cord injury is a traumatic condition that causes severe morbidity and high mortality. In this work we describe in detail a contusion model of spinal cord injury in mice followed by a transplantation of neural stem cells.

Spinal cord injury is a devastating clinical condition, characterized by a complex of neurological dysfunctions. Animal models of spinal cord injury can ...

Calibrated Forceps Model of Spinal Cord Compression Injury

Compression injuries of the murine spinal cord are valuable animal models for the study of spinal cord injury (SCI) and spinal regenerative therapy. The calibrated forceps model of compression injury is a convenient, low cost, and very reproducible animal model for SCI. We used a pair of modified forceps in accordance with the method published by Plemel et al. (2008) to laterally compress the spinal cord to a distance of 0.35 mm. In this video, we will demonstrate a dorsal laminectomy to expose the spinal cord, followed by compression of the spinal cord with the modified forceps. In the video, we will also address issues related to the care of paraplegic laboratory animals. This injury model produces mice that exhibit impairment in sensation, as well as impaired hindlimb locomotor function. Furthermore, this method of injury produces consistent aberrations in the pathology of the SCI, as determined by immunohistochemical methods. After watching this video, viewers should be able to determine the necessary supplies and methods for producing SCI of various severities in the mouse for studies on SCI and/or treatments designed to mitigate impairment after injury.

Spinal cord injury models should be highly reproducible. We demonstrate that the calibrated forceps compression model of spinal cord injury is an easy to use surgical method for generating reproducible injuries to the murine spinal cord.

Compression injuries of the murine spinal cord are valuable animal models for the study of spinal cord injury (SCI) and spinal regenerative therapy. The ...

A Neonatal Mouse Spinal Cord Compression Injury Model

Spinal cord injury (SCI) typically causes devastating neurological deficits, particularly through damage to fibers descending from the brain to the spinal cord. A major current area of research is focused on the mechanisms of adaptive plasticity that underlie spontaneous or induced functional recovery following SCI. Spontaneous functional recovery is reported to be greater early in life, raising interesting questions about how adaptive plasticity changes as the spinal cord develops. To facilitate investigation of this dynamic, we have developed a SCI model in the neonatal mouse. The model has relevance for pediatric SCI, which is too little studied. Because neural plasticity in the adult involves some of the same mechanisms as neural plasticity in early life1, this model may potentially have some relevance also for adult SCI. Here we describe the entire procedure for generating a reproducible spinal cord compression (SCC) injury in the neonatal mouse as early as postnatal (P) day 1. SCC is achieved by performing a laminectomy at a given spinal level (here described at thoracic levels 9-11) and then using a modified Yasargil aneurysm mini-clip to rapidly compress and decompress the spinal cord. As previously described, the injured neonatal mice can be tested for behavioral deficits or sacrificed for ex vivo physiological analysis of synaptic connectivity using electrophysiological and high-throughput optical recording techniques1. Earlier and ongoing studies using behavioral and physiological assessment have demonstrated a dramatic, acute impairment of hindlimb motility followed by a complete functional recovery within 2 weeks, and the first evidence of changes in functional circuitry at the level of identified descending synaptic connections1.

This article describes a method for generating a reproducible spinal cord compression injury (SCI) in the neonatal mouse. The model provides an advantageous platform for studying mechanisms of adaptive plasticity that underlie spontaneous functional recovery.

Spinal cord injury (SCI) typically causes devastating neurological deficits, particularly through damage to fibers descending from the brain to the spinal ...