Studies were completed as part of a team supported by The Moody Project for Translational Traumatic Brain Injury Research and award W81XWH-08-2-0132 from the U.S. Army Medical Research and Material Command - Department of Defense.

All experimental protocols were approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Texas Medical Branch, an Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC) accredited facility.
1. Animal Preparation for ABS Blast Injury
<ol>
	<li>Turn on mechanical rodent volume ventilator and set breath rate between 40&#8211;45 breaths per min.</li>
	<li>Switch thermostatically controlled warming blanket ON and tape a blue pad over it.</li>
	<li>Attach ventilator hose to the ventilator.</li>
	<li>Gather endotracheal intubation sled, laryngoscope, long pickup tweezers, stylet, endotracheal tube, and a cotton swab soaked with 0.05 mL of 1% Lidocaine HCl. Organize on the blue pad.</li>
	<li>Confirm that rodent anesthetic &#34;bubble&#34; chamber, ventilator, air chamber and isoflurane chamber hoses are securely connected and attached to their respective plug or socket. The anesthetic bubble chamber clamp should be OPEN; the ventilator clamp should be CLOSED.</li>
	<li>On the air chamber, set the knob for room air to 2 L/min and the knob for oxygen to 1 L/min.</li>
	<li>Turn on the isoflurane and set the knob to 4% of volume mixture.</li>
	<li>Start a timer and place a young adult (&#8776;3 months old), male Sprague-Dawley rat (350&#8211;400 g) in the anesthetic bubble chamber for 4&#8211;6 min.</li>
	<li>Weigh rat at the 2 min mark.</li>
	<li>Confirm rat is fully anesthetized by gently pinching hind paw toes. If no paw withdrawal is observed, reduce the room air and set knob to 1 L/min, oxygen to 0.4 L/min and isoflurane to 2% of volume mixture.</li>
	<li>Turn on rectal telethermometer temperature monitor.</li>
	<li>OPEN the clamp to the ventilator and CLOSE the clamp to the anesthetic bubble chamber.</li>
	<li>Remove rat from anesthetic bubble chamber and position on endotracheal intubation sled.</li>
	<li>Intubate rat. Place laryngoscope in animal&#39;s mouth, use long pickup tweezers to position the tongue out of the way, swab lidocaine-soaked cotton swab tip along inside of the throat and gently insert stylet containing the endotracheal tube into rat&#39;s trachea.</li>
	<li>Once intubated, insert the end of the ventilator hose to the outside end of endotracheal tube and observe and confirm the rat is breathing steadily and without difficulty.</li>
	<li>Tie down the endotracheal tube into place taking care that the tongue is free from the knot.</li>
	<li>Apply white petroleum jelly to rectal telethermometer probe and insert directly beneath the tail.</li>
	<li>Remove the ABS specimen tray from the specimen chamber and place under the heat lamp for warming before rat placement on tray.</li>
	<li>Shave the top of the rat&#39;s scalp starting above the eyes and down to between the ears.</li>
	<li>Cut a standard-sized foam ear plug into identical halves with scissors. Start at the center of the base of the plug and cut straight up to the rounded tip. Insert a halved piece into each ear tip first along the ear canal until contact is made with the tympanic membrane.</li>
	<li>Monitor rectal temperature. Once a temperature of 37 &#176;C is reached, the rat is ready to be loaded into the ABS specimen tray.</li>
	<li>Secure the rat onto the ABS specimen tray. Remove the ventilator hose from the endotracheal tube and quickly but softly slide the rat into the top end of the tray, gently guiding the head through the head holder opening and rubber collar. Reinsert the ventilator hose back into the endotracheal tube, check the rubber collar to make sure it is securely but not tightly around the neck and verify that the rat is laying in a lateral prone position (Figure 3).</li>
	<li>Turn off the isoflurane and remove the ventilator hose from the endotracheal tube.</li>
	<li>Lock and secure the ABS specimen tray containing the anesthetized rat into the ABS specimen chamber.</li>
	<li>Gently pinch hind paw toes using long tweezers every 3 s until a withdrawal reflex response is elicited.</li>
</ol>
2. ABS Blast Device Preparation and Blast-TBI Induction
NOTE: Protocol steps 2.1&#8211;2.10 are typically completed at the same time as steps 1.1&#8211;1.22 so the ABS is ready for blast injury administration right after the rat is loaded and secured into the specimen chamber.
<ol>
	<li>Loosen the hydraulic hand pump (Figure 4A) knob in order to allow for any residual trapped air to escape from the driver chamber (Figure 4B) and to loosen the chamber from its seal.</li>
	<li>Loosen the cap nuts (Figure 4C) from the all-thread rods (Figure 4D) surrounding the driver chamber and slide the chamber to the left and away from the expansion chamber (Figure 4E).</li>
	<li>Completely remove the two all-thread rods and their corresponding cap nuts located at the top of the driver chamber in order to allow for placement of the mylar sheets in between the driver and expansion chamber.</li>
	<li>Stack and tape together along the top edge four pre-cut and pre-measured (30 cm length, 20 cm width, 0.004 in. thick) mylar sheets (forming a mylar &#39;membrane&#39;) using a 2.54 cm piece of masking tape. Using a second piece of tape, securely tape the top edge of the mylar membrane to the top of the expansion chamber and over the center of the opening between the driver and expansion chambers (Figure 4F).</li>
	<li>Secure the driver chamber against the mylar membrane by replacing the two all-thread rods at the top of the chamber and hand-tightening all cap nuts surrounding the chamber.</li>
	<li>Situate the accessory steel block against the hydraulic hand pump block and driver chamber until securely fit.</li>
	<li>Tighten the hydraulic hand pump knob and confirm the driver chamber remains pressurized with no leaks by observing a constant pressure threshold on the hydraulic gauge.</li>
	<li>Open the trigger acquisition file that records ABS blast device pressure traces on the ABS blast device computer.</li>
	<li>Loosen the compressed air tank&#39;s (Figure 4G) main knob enough to slightly open the airway.</li>
	<li>Operate the hydraulic hand pump until the gauge indicator reaches the red arrow indicating a desired chamber pressure level of &#8776;5,000 psi.</li>
	<li>Secure and position the anesthetized animal onto the ABS specimen tray (Figure 4H) in a lateral prone position (Figure 3) and lock the specimen tray into the ABS specimen chamber (Figure 4I).</li>
	<li>Gently pinch a hind paw using long tweezers every 3 s until a withdrawal reflex response is elicited.</li>
	<li>Click Start on the opened acquisition page on the ABS blast device computer.</li>
	<li>Once the &#39;Acquisitioning&#39; window appears on the screen, press and hold down the ABS blast device trigger until the blast goes off, rupturing the mylar membrane and administering the ABS blast injury (20.9 psi &#177;1.14, 138 kPa &#177;7.9) to the rat. Right after the blast detonates, start a second timer to keep track of how much time (in min and s) has elapsed post-injury.</li>
	<li>Remove the rat from the ABS specimen tray and return to the blue pad and warming blanket, placing him fully on his back for assessment of righting reflex suppression.</li>
	<li>Record the time for return of the righting reflex. Observing the second timer, document in min and s the length of time post-injury it takes for the rat to roll from his back onto his stomach three successive times. Return the rat to the anesthetic bubble chamber.</li>
	<li>Loosen the hydraulic hand pump knob in order to allow for driver chamber loosening and movement.</li>
	<li>Tighten the compressed air tank&#39;s main knob in order to close the airway.</li>
</ol>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/58792/58792fig3.jpg" /> 
Figure 3: Rat placement on ABS specimen tray and inside ABS. Direction and orientation of the study animal inside the ABS. When placed in the ABS, the animal is in a transverse prone position with the dorsal surface of the head perpendicular to the shock wave direction (red arrows). <a href="https://www.jove.com/files/ftp_upload/58792/58792fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/58792/58792fig4.jpg" /> 
Figure 4:&#160;Advanced Blast Simulator (ABS) shock tube device schematic. Major components of the ABS. A = hydraulic hand pump; B = driver chamber; C = cap nuts; D = all-thread rods;&#160; E = expansion chamber; F = location of mylar membrane placement; G = compressed air cylinders; H = specimen tray; I = specimen chamber.&#160;&#160;<a href="https://www.jove.com/files/ftp_upload/58792/58792fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Preparation of Rodent MCA PSS Solution
NOTE: Protocol steps 3.1&#8211;3.3 are typically completed at the same time as steps 1.1&#8211;1.22 to have the PSS solution is ready for use.
<ol>
	<li>Prepare and mix a 1,000 mL physiological salt solution (PSS) of the following composition and concentrations: 130 mM NaCl; 4.7 mM KCl; 1.17 mM MgSO4&#8729;7H2O; 5 mM glucose; 1.5 mM CaCl2; 15 mM NaHCO3.</li>
	<li>Equilibrate the PSS with a gas mixture of 21% O2 and 5% CO2 in a balance of N2. The solution is ready when the pH reads 7.4. 
	NOTE: All gases are obtained from compressed gas cylinders in the above mentioned concentrations.</li>
	<li>Fill the reservoir bottles and tubing with prepared PSS solution and chill the remaining solution.</li>
</ol>
4. Extraction of Rodent MCA Segments
<ol>
	<li>After documenting the length of the righting reflex time, return the rat to the anesthetic bubble chamber. CLOSE the clamp to the ventilator, and OPEN the clamp to the chamber. Turn the isoflurane on to 4% of volume mixture and keep the rat in the chamber for 2&#8211;3 min until deeply anesthetized.</li>
	<li>Once the rat is anesthetized, OPEN the clamp to the ventilator and CLOSE the clamp to the anesthetic bubble chamber. Reduce the isoflurane to 2% of volume mixture, and remove him from the bubble chamber. Place him on his stomach on the warming blanket and re-insert the end of the ventilator hose to the outside end of endotracheal tube.</li>
	<li>Maintain mechanical ventilation at a breath rate between 40&#8211;45 breaths per min and anesthesia at 2% of volume mixture for either 30 or 60 min immediately post-bTBI injury.</li>
	<li>After completion of either the 30 or 60 min survival time, increase the isoflurane to 4% of volume mixture, and deeply anesthetize for 5&#8211;6 min.&#160;Immediately euthanize by decapitation using a rodent-specific guillotine. 
	NOTE: In these experiments, we kept the animals anesthetized and mechanically ventilated following the return of righting reflex until decapitation.&#160; If the study requires longer survival timepoints, analgesics should be administered to the animal before emergence from anesthesia.&#160;</li>
	<li>Delicately remove the brain from the skull. Use a #10 scalpel blade to make a central, 1.5 inch vertical, bone-deep incision from the top of the shaved scalp down to the occipital condyle.</li>
	<li>Use small bone rongeurs to open and separate the scalp skin from the skull bone.</li>
	<li>Use large bone rongeurs to cut and extract the occipital, interparietal, and lower half of the frontal bones encasing the brain.</li>
	<li>Use a surgical spatula to carefully excavate the brain out of the skull once the brain is free of surrounding bone. 
	NOTE: Take extreme caution when separating the brain from the skull so as not to unnecessarily tug, jerk or pull the delicate MCA segments from the cranial wall.</li>
	<li>Deposit the harvested brain into the chilled PSS solution contained in a small glass Petri dish that is directly resting on top of a solid ice-block.</li>
	<li>Carefully remove both the left and right MCA beginning at the Circle of Willis. Continue removing the segment laterally and dorsally for approximately 4&#8211;5 mm.</li>
	<li>Gently clean the collected MCA segments of approximately 4&#8211;5 mm in length of any connective tissue using microforceps.</li>
	<li>Mount the MCA&#39;s on the arteriograph. Cannulate the proximal end of each segment with the first glass micropipette (diameter &#8776;70 &#181;m) and secure with a 10-0 nylon suture.</li>
	<li>Softly perfuse the lumina with PSS to remove any residual blood and other contents from the lumen.</li>
	<li>Cannulate the distal end of each segment with the second micropipette without stretching the MCA segment and secure with a 10-0 nylon suture.</li>
	<li>After successful mounting of the MCA segment, place the chamber on top of an inverted microscope&#39;s stage for magnification of the vessels. The microscope is equipped with a video camera, monitor and a video scaler calibrated with an optical micrometer for arterial diameter measurements.</li>
	<li>Fill each segment and the surrounding arteriograph bath with continuously circulated PSS warmed from room temperature to 37 &#176;C and equilibrated with the gas mixture of 21% O2 and 5% CO2 in a balance of N2.</li>
	<li>Equilibrate the MCA segments at a pressure of 50 mmHg for 60 min by raising the reservoir bottles connected to the micropipettes to an appropriate height above the segments.Pressure transducers located between the micropipettes and reservoir bottles will assess transmural pressure within the MCA segment indicating when the desired 50 mmHg pressure is attained.</li>
	<li>After the conclusion of the equilibration period, increase the intravascular pressure to 100 mmHg by setting the reservoir bottles at different heights.</li>
	<li>Deliver 30 mM K+ (for confirmation of vessel contraction) via the luminal perfusate and measure arterial diameters. Approximately 10 min later deliver 10-5 M Ach (for vessel dilation) and measure arterial diameters.</li>
	<li>Examine vessel dilatory responses. Lower the reservoir bottles to reduce the intravascular pressure from 100 mmHg to 80 mmHg. Allow the MCA segments to equilibrate for 10 min. Measure arterial diameters.</li>
	<li>Reduce the intravascular pressure from 80 mmHg to 60 mmHg. Allow the MCA segments to equilibrate for 10 min. Measure arterial diameters.</li>
	<li>Reduce the intravascular pressure from 60 mmHg to 40 mmHg. Allow the MCA segments to equilibrate for 10 min. Measure arterial diameters.</li>
	<li>Reduce the intravascular pressure from 40 mmHg to 20 mmHg. Allow the MCA segments to equilibrate for 10 min. Measure arterial diameters.</li>
</ol>

The authors have nothing to disclose.

As with all protocols and instructions, it is imperative that certain steps for the protocol in this particular study are followed as accurately and as precisely as possible. After the initial intubation of the rat it is important to confirm that it is breathing steadily and without difficulty. Mistakenly inserting the endotracheal tube into the esophagus instead of the trachea will result in rasping, difficult breaths, bleeding and the subsequent rousing of the rat due to deficient anesthetic delivery to the lungs.
When taping the mylar membrane sheets over the center of the opening between the driver and expansion chamber, it is imperative that the sheets are centered and cover the entire opening39,41. Misaligning the sheets over the opening will result in air leakage from the driver chamber, a drop in the required pressure for membrane burst-potential and denial of administration of the blast injury. Properly situating and securely fitting the accessory steel block against the hydraulic hand pump block and driver chamber is also essential as is tightening the hydraulic hand pump knob and confirming the driver chamber remains pressurized without leaks. Proper placement of the steel block allows for the driver chamber to tightly close against the expansion chamber, thus creating the mandatory seal required over the chamber opening by the Mylar membrane sheets and between the driver and expansion chamber.
During preparations before the MCA vessel extractions, gassing the PSS with the requisite mixture of 21% O2 and 5% CO2 in a balance of N2 equilibrates the solution and facilitates the necessitated neutral physiological pH needed for a working PSS solution21,33,34.
Equilibrating the segments at a constant pressure for 60 min21,32,33,34 is extremely obligatory as this step permits the segments to constrict following a maximum dilation displayed during their first primary pressurization. This event demonstrates the occurrence of spontaneous tone, a property suggestive of a healthy artery32,33,34. Though assorted pressure levels for segment equilibration have been utilized in other studies33,34,42, this study and those of Mathew et al.21, Golding et al.35 and Golding et al.43 equilibrated the segments at 50 mmHg. While equilibrating collected segments anywhere between 40 mmHg&#8211;100 mmHg32 allows for some flexibility and modification for that step of the protocol, an hour equilibration period within those pressure parameters ultimately confirms healthy arteries needed for continuation of the experiment.
Taking extreme caution when removing the brain from the skull and the left and right MCA segments from the Circle of Willis while keeping those vessels intact is perhaps the most critical step of the entire protocol. Puncturing the brain with the bone rongeurs, tearing or severe stretching of the segments during removal or accidentally pulling the vessels with the surgical spatula when excavating the brain out of the skull will ultimately result in destruction of the harvested MCA&#39;s, causing unserviceable segments and discontinued use of that set of arteries, ultimately voiding the entire experiment for that animal.
Though measuring cerebral vascular responses to dilatory or constrictory stimuli in MCA segments ex vivo collected after impact or blast TBI in vivo has yielded success, the methodology is not without its difficulties and/or limitations. Perhaps one of the more discernable complexities linked with examining the consequences of TBI on the circulation of the cerebral vasculature is detaching the explicit effects of TBI on the vessels from the implicit effects incurred due to the various materials and elements generated by the injured brain44. This conceivable perplexity can potentially be evaded by analyzing ex vivo the vasoconstrictory and vasodilatory reactions of harvested, perfused and/or pressurized MCA&#39;s. In an effort to reduce the duration of time that cerebral arteries in vivo are exposed to locally discharged parenchymal vasoactive material prior to death, collection of the cerebral arteries directly after TBI can lessen the degree of such prolonged-exposure effects. Ex vivo studies on isolated MCA&#39;s additionally present the prospect of analyzing mechanisms of traumatic vascular injury through the use of particular receptor agonists and antagonists or reputed vehicles of vascular injury that would not afford scrutiny as efficiently or as discriminatory in vivo. Subsequently, this ex vivo method can be combined with ex vivo exposure to drugs to test resulting myogenic responses (vasoconstriction or dilation of vessel segment due to intravascular or extravascular drug exposure).
Other limitations include roughly or impatiently removing the MCA&#39;s from the harvested brain which can result in premature tearing of the vessels, thus voiding their use. In addition, letting more than a few minutes elapse between euthanasia of the animal, collection of the vessels and their placement in the prepared PSS solution can also negate their viability. When properly performed and followed, the methods described in this protocol for testing myogenic responses of MCA&#39;s after bTBI takes several hours from start to finish and attempts at curtailing the length of time required for success can result in experimental failure. However, this method is done in vitro and utilizes considerably more cost-effective instrumentation and equipment than in vivo high-resolution magnetic resonance (MR) imaging45,46 or conventional Doppler sonography/velocimetric techniques47,48,49 which are also employed for vessel studies.
These findings that mild bTBI injury is associated with impaired cerebral dilatory responses to reduced intravascular pressure could potentially be a function of the vasospasm6,7 and VSMC hyperconstriction50 previously reported after blast exposure ultimately leading to occurrences such as reduced relative cerebral perfusion. Additionally, blast-induced damage hampering normal dilatory reactions of the cerebral vasculature could possibly promote further reductions in cerebral perfusion when combined with arterial hypotension, a frequent incidence during combat operations.
These results indicate that bTBI results in a change to the mechanisms facilitating arterial vascular control. Though acute-phase cerebral vascular impairment of arterial myogenic response to reductions in intravascular pressure for at least an hour post-injury were observed, there remain gaps in information surrounding the acute phase after bTBI. The importance of identifying what physical and biochemical deficiencies injuries to the cerebral vasculature and the brain exposure to bTBI causes could aid in determining the level of therapeutic and/or rehabilitative success fairly immediately after injury.

Similar to that resulting from impact (i.e., non-blast) TBI, blast-induced traumatic brain injury (bTBI) has been associated with cerebral vascular injury1 and impaired cerebral vascular compensatory responses to occurrences like alterations in the partial pressures of carbon dioxide (PaCO2)2,3,4 and oxygen (PaO2)5. Additionally, blast exposure has caused cerebral arterial vasospasm in animals6 and bTBI patients7,8. While clinical TBI9 and fluid-percussion injury (FPI)10,11,12 are associated with impaired cerebral vascular responses to changes in arterial blood pressure (i.e., pressure autoregulation)9,10,11,12, uncertainties remain concerning the effects of bTBI on cerebral vascular pressure autoregulation capacity.
The cerebral circulation reacts to variations in systemic arterial pressure with the intent of maintaining a continuous oxygen and nutrient supply delivered to the metabolically active brain13,14,15,16. A unique type of homeostasis, autoregulation17,18,19 occurs when &#34;an organ maintains a constant blood flow despite changes in blood (perfusion) pressure or other physiologic or pathologic stimuli&#34;20. Cerebral arteries constrict or dilate in response to variations in blood pressure, nitric oxide (NO), blood viscosity, PaCO2 and PaO2, etc.4,11,16,21. Arterial myogenic response refers to such contractions or dilations. The myogenic vascular response, first described by Bayliss22 and a major mechanism contributing to autoregulation of CBF, is characterized by vasoconstriction if perfusion pressure increases and vasodilatation if perfusion pressure decreases14,17. This vascular response is the inherent ability of contractile tissues (such as vascular smooth muscle cells, VSMC&#39;s) to respond to stretch and/or changes in lumen and/or wall tension23,24,25,26,27,28,29. When arteries are stretched (e.g., during intravascular pressure increases), VSMC&#39;s constrict24,25,26,28.
Studies that examine resistance vessels ex vivo have commonly employed one of two methods for testing the pharmacological and physiological properties of isolated resistance vessels: the ring-mounted method and the cannulated, pressurized method. The ring-mounted vessel preparation method involves two wires passed intraluminally through the vessel segment, which hold the segment in place. Measuring the amount of force applied on the isometrically sustained wires gauges the stimulation of the VSMC&#39;s. However, this technique carries with it certain reservations, most notably, the inevitable damage sustained by the endothelial layer of the lumen as the wires are passed through it30 and the varying degree of stretching sustained by the isolated segment which in turn leads to vessel wall distension, ultimately affecting the vessel&#39;s sensitivity to pharmacological agents31. The cannulated, pressurized vessel preparation methodology utilizes an arteriograph comprised of two separate chambers that each house the placement of a middle cerebral arterial (MCA) harvested from a single animal. A micropipette is inserted into each end of the segment, the proximal end of the segment is fastened to the micropipette with sutures and the lumen is softly perfused with a physiological salt solution (PSS) in order to eliminate blood and any other substances. The distal end is then secured with sutures. Transmural or luminal pressure is set by raising the two reservoirs attached to each pipette to a suitable height above each segment but at different heights with respect to the other32,33,34,35,36. Pressure transducers positioned along the reservoirs and micropipettes provide perfusion pressure measurements while vessels are magnified using an inverted microscope outfitted with a monitor, video camera and scaler allowing for measurement of the external MCA diameters. Though both methods are valuable, the cannulated, pressurized vessel preparation methodology better mimics and permits the vessels investigated to be closer to their in vivo conditions32,37.
The effects of different types of impact (i.e., non-blast) TBI on cerebral vascular responses have previously been studied in cerebral arterial segments21,35,36,38. Using a similar ex vivo MCA protocol for vessel collection, mounting and perfusion as described in the current study, earlier studies obtained success with their respective investigations into the associated mechanisms of cerebral vasculature dysfunction following TBI. Golding et al.34 examined endothelial-mediated dilations in adult, male Long-Evans rat MCA&#39;s following severe TBI through controlled cortical impact (CCI) injury. In a second study, Golding et al.36 investigated cerebrovascular reactivity to hypotension or CO2 after harvesting MCA&#39;s from rats that sustained a mild CCI. Yu et al.38 analyzed whether peroxynitrite scavengers improved dilatory responses to reduced intravascular pressure in adult, male Sprague-Dawley rat MCA segments subjected to FPI while Mathew et al.21 studied myogenic responses to hypotension in MCA&#39;s harvested after moderate, central FPI.
To better investigate the hypothesis that bTBI, like non-blast TBI, results in impaired cerebral vascular reactivity, we tested a mechanism contributing to compromised autoregulation by measuring myogenic dilatory responses to reduced intravascular pressure ex vivo in isolated, pressurized rodent MCA segments (Figure 1) collected from rats subjected to mild bTBI using an Advanced Blast Simulator (ABS) shock tube model (Figure 2 and Figure 3) (see Rodriguez et al.39&#160;Table 1) that uses compressed air delivered directly to a driver chamber to generate Freidlander-like40 over- and under-pressure waves (see Rodriguez et al.39 Figure 1A).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58792/58792fig1.jpg" /> 
Figure 1: Location of middle cerebral arteries (MCA). Ventral view of the rat brain highlighting the location of the MCA&#39;s relative to the posterior cerebral arteries (PCA), internal carotid arteries (ICA), external carotid arteries (ECA), basilar artery (BA) and common carotid arteries (CCA). <a href="https://www.jove.com/files/ftp_upload/58792/58792fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/58792/58792fig2.jpg" /> 
Figure 2: Advanced Blast Simulator (ABS) shock tube device. The ABS used to produce primary blast injury in all study animals. 1 = driver chamber; 2 = expansion chamber;&#160; 3 = specimen chamber; 4 = reflected wave suppressor;&#160;yellow star = specimen tray. <a href="https://www.jove.com/files/ftp_upload/58792/58792fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

<table><tbody><tr><td>Advanced Blast Simulator (ABS)</td><td>Dyn-FX Consulting, Ltd. and ORA, Inc.</td><td>N/A</td><td>Blast-simulating shock tube used to induce primary blast injuries&amp;nbsp;</td></tr><tr><td>Adult, male, Sprague-Dawley rats&amp;nbsp;</td><td>Charles River Laboratories</td><td>N/A</td><td>Experimental animals</td></tr><tr><td>Arteriograph</td><td>Living Systems Instrumentation, Inc.</td><td>Arteriograph</td><td>Mounting of harvested arteries and measurement of lumen diameter&amp;nbsp;</td></tr><tr><td>Bone rongeurs, large</td><td>FST Fine Science Tools</td><td>Friedman Rongeur</td><td>Brain extraction from skull</td></tr><tr><td>Bone rongeurs, small</td><td>FST Fine Science Tools</td><td>Boynton Rongeur</td><td>Brain extraction from skull</td></tr><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt;&amp;nbsp;</td><td>Sigma</td><td>Calcium chloride</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>Ear plugs</td><td>3M</td><td>Foam Ear Plugs 1100 Class AL&amp;nbsp;</td><td>Prevent injury of ear tympanic membrane when in the blast machine&amp;nbsp;</td></tr><tr><td>Glucose</td><td>Sigma</td><td>D-[+]-Glucose</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>Isoflurane&amp;nbsp;</td><td>Piramal Enterprises Limited&amp;nbsp;</td><td>Isoflurane, USP</td><td>Anesthetic</td></tr><tr><td>KCl</td><td>Sigma</td><td>Potassium chloride</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>MgSO&lt;sub&gt;4&lt;/sub&gt;&amp;bull;7H&lt;sub&gt;2&lt;/sub&gt;O&amp;nbsp;</td><td>Sigma</td><td>Magnesium sulfate</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>Microforceps</td><td>Buxton Biomedical Inc.</td><td>Micro Tying Fcps, 180mm</td><td>Brain extraction from skull</td></tr><tr><td>Mylar sheets</td><td>Texas Art Supply</td><td>Mylar</td><td>Membrane used for compressed air build-up during blasting</td></tr><tr><td>NaCl</td><td>Sigma</td><td>Sodium chloride</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;</td><td>Sigma</td><td>Sodium bicarbonate</td><td>Preparation of rodent middle cerebral arterial physiological salt solution (PSS)</td></tr><tr><td>Nylon suture</td><td>Ethicon</td><td>10-0 Ethilon nylon suture black monofilament 5&quot; (13 cm)</td><td>Mounting of harvested arteries and measurement of lumen diameter&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;</td></tr><tr><td>Scalpel blade #10</td><td>Bard-Parker</td><td>10 Stainless Steel Surgical Blade</td><td>Brain extraction from skull</td></tr><tr><td>Surgical spatula</td><td>Delmaks Surgico</td><td>Cement Spatula&amp;nbsp;</td><td>Brain extraction from skull</td></tr><tr><td>Thermometer&amp;nbsp;</td><td>Physitemp Instruments, Inc.,&amp;nbsp;</td><td>Thermalert Monitoring Thermometer</td><td>Monitoring of experimental animal&#039;s core body temperature&amp;nbsp;</td></tr><tr><td>Volume ventilator&amp;nbsp;</td><td>Harvard Apparatus, Inc.</td><td>Small Animal Ventilator</td><td>Constant and steading breathing of the intubated experimental animal</td></tr><tr><td>Water blanket</td><td>Gaymar Industries, Inc.&amp;nbsp;</td><td>Mul-T-Pad Temperature Therapy Pad</td><td>Maintenance of experimental animal&#039;s body temperature&amp;nbsp;</td></tr></tbody></table>

effects of blast-induced neurotrauma on pressurized rodent middle cerebral arteries

Though there have been studies on the histopathological and behavioral effects of blast exposure, fewer have been dedicated to blast&#39;s cerebral vascular effects. Impact (i.e., non-blast) traumatic brain injury (TBI) is known to decrease pressure autoregulation in the cerebral vasculature in both humans and experimental animals. The hypothesis that blast-induced traumatic brain injury (bTBI), like impact TBI, results in impaired cerebral vascular reactivity was tested by measuring myogenic dilatory responses to reduced intravascular pressure in rodent middle cerebral arterial (MCA) segments from rats subjected to mild bTBI using an Advanced Blast Simulator (ABS) shock tube. Adult, male Sprague-Dawley rats were anesthetized, intubated, ventilated and prepared for Sham bTBI (identical manipulation and anesthesia except for blast injury) or mild bTBI. Rats were randomly assigned to receive Sham bTBI or mild bTBI followed by sacrifice 30 or 60 min post-injury. Immediately after bTBI, righting reflex (RR) suppression times were assessed, euthanasia at the time points post-injury was completed, the brain was harvested and the individual MCA segments were collected, mounted and pressurized. As the intraluminal pressure perfused through the arterial segments was reduced in 20 mmHg increments from 100 to 20 mmHg, MCA diameters were measured and recorded. With decreasing intraluminal pressure, MCA diameters steadily increased significantly above baseline in the Sham bTBI groups while MCA dilator responses were significantly reduced (p &#60; 0.05) in both bTBI groups as evidenced by the impaired, smaller MCA diameters recorded for the bTBI groups. In addition, RR suppression in the bTBI groups was significantly (p &#60; 0.05) higher than in the Sham bTBI groups. MCA&#39;s collected from the Sham bTBI groups exhibited typical vasodilatory properties to decreases in intraluminal pressure while MCA&#39;s collected following bTBI exhibited significantly impaired myogenic vasodilatory responses to reduced pressure that persisted for at least 60 min after bTBI.

Mean bTBI overpressure for all study animals was 20.9 psi &#177;1.14 (138 kPa &#177;7.9). The mean duration of righting reflex (RR) suppression for rats subjected to ABS bTBI shockwave exposure (5.37 min &#177;2.1) was not significantly longer (p = 0.36, bTBI vs. sham) than in the sham group (5.10 min &#177;1.6).
In both the 30 and 60 min sham groups, MCA diameters increased above baseline as intraluminal pressure was reduced from 100 to 20 mmHg. Compared to their corresponding sham groups, the MCA dilatory responses to the continuous imposed reduction in intravascular pressure in the observed 30 min (p = 0.01, bTBI vs. sham) and 60 min (p = 0.02, bTBI vs. sham) ABS bTBI groups were significantly reduced after blast exposure (Figure 5). For a more detailed discussion of these results, see Rodriguez et al.39.
These studies revealed that mild bTBI significantly impaired cerebral compensatory dilator responses to reduced intravascular pressure in MCA segments 30 and 60 min after mild bTBI while the mild shock wave levels used in these studies resulted in durations of suppression of RR (&#60;30 s) similar to those in sham-injured rats.
Statistical analyses were performed with software. The myogenic response to changes in intravascular pressure was assessed by calculating percent change from baseline (100 mmHg) for each level of intraluminal pressure (80, 60, 40, and 20 mmHg). Unpaired Student&#39;s t-tests were used to evaluate differences between the bTBI and sham group baselines. Differences in MCA dilator responses between bTBI and sham groups were assessed using a repeated one-way analysis of variance (ANOVA) Dunnett&#39;s multiple comparisons test and a Bartlett&#39;s test for equal variance.
Due to the reduction in statistical power that results from repeated testing, comparisons at each specific pressure point in the MCA experiments (e.g., between 100 and 80 mmHg or between 60 and 40 mmHg, etc.) were not conducted. Significance was accepted at the p &#8804; 0.05 level. All data in the text, referenced table, and figure is expressed as means &#177; standard errors of the means (SEM).
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/58792/58792fig5.jpg" /> 
Figure 5: Effects of bTBI on middle cerebral arterial (MCA) responses to reduced intravascular pressure. Dilator responses to progressive reductions in intravascular pressure exhibited impaired vasodilatory responses and were significantly reduced in the 30 min (p = 0.01, bTBI vs. sham) and 60 min (p = 0.02, bTBI vs. sham) bTBI groups (n = 6/group) after blast exposure compared to both Sham groups (n = 12). In both the 30 and 60 min sham groups, MCA diameters increased above baseline as intraluminal pressure was reduced from 100 to 20 mmHg. Values are plotted as means &#177; SEM. *p &#60; 0.05 vs. sham. <a href="https://www.jove.com/files/ftp_upload/58792/58792fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Effects of Blast-induced Neurotrauma on Pressurized Rodent Middle Cerebral Arteries at JoVE.com

Effects of Blast-induced Neurotrauma on Pressurized Rodent Middle Cerebral Arteries

Here, we present a protocol to describe methods for ex vivo vascular reactivity determination following a primary blast traumatic brain injury (bTBI) using isolated, pressurized, rodent middle cerebral arterial (MCA) segments. bTBI induction is accomplished using a shock tube, also known as an Advanced Blast Simulator (ABS) device.

Though there have been studies on the histopathological and behavioral effects of blast exposure, fewer have been dedicated to blast&#39;s cerebral ...

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Neuroscience

7.2K Views.  University of Texas Medical Branch. Deze methode helpt om te beantwoorden of blast traumatisch hersenletsel resulteert in cerebrale vasculaire letsel en als de reikwijdte van de effecten zich uitstrekt tot een verminderde myogene vasculaire respons. De geïsoleerde arteriële voorbereiding onder druk stelt ons in staat om de directe effecten van blootstelling aan de explosie op cerebrale slagaders te scheiden van de indirecte effecten veroorzaakt door blootstelling aan de hersenen. Geïsoleerde en onder druk staande arteriële ...

Video: Effects of Blast-induced Neurotrauma on Pressurized Rodent Middle Cerebral Arteries

Focal Cerebral Ischemia Model by Endovascular Suture Occlusion of the Middle Cerebral Artery in the Rat

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable clinical state; in the development of animal models of focal ischemia, however, achieving reproducibility of experimentally induced infarct volume is essential. The rat is a widely used animal model for stroke due to its relatively low animal husbandry costs and to the similarity of its cranial circulation to that of humans2,3. In humans, the middle cerebral artery (MCA) is most commonly affected in stroke syndromes and multiple methods of MCA occlusion (MCAO) have been described to mimic this clinical syndrome in animal models. Because recanalization commonly occurs following an acute stroke in the human, reperfusion after a period of occlusion has been included in many of these models. In this video, we demonstrate the transient endovascular suture MCAO model in the spontaneously hypertensive rat (SHR). A filament with a silicon tip coating is placed intraluminally at the MCA origin for 60 minutes, followed by reperfusion. Note that the optimal occlusion period may vary in other rat strains, such as Wistar or Sprague-Dawley. Several behavioral indicators of stroke in the rat are shown. Focal ischemia is confirmed using T2-weighted magnetic resonance images and by staining brain sections with 2,3,5-triphenyltetrazolium chloride (TTC) 24 hours after MCAO.

Surgical induction of ischemic brain damage in the rat is a widely used model for stroke research. Here we demonstrate the induction of focal cerebral ischemia by occlusion of the middle cerebral artery. Visualization of the resulting infarct by histological staining and magnetic resonance imaging is also shown.

Stroke is the leading cause of disability and the third leading cause of death in adults worldwide1. In human stroke, there exists a highly variable ...

Mouse Model of Middle Cerebral Artery Occlusion

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the brain (ischemic stroke) 2. Since most ischemic strokes (~80%) occur in the territory of middle cerebral artery (MCA) 3, many animal stroke models that have been developed have focused on this artery. The intraluminal monofilament model of middle cerebral artery occlusion (MCAO) involves the insertion of a surgical filament into the external carotid artery and threading it forward into the internal carotid artery (ICA) until the tip occludes the origin of the MCA, resulting in a cessation of blood flow and subsequent brain infarction in the MCA territory 4. The technique can be used to model permanent or transient occlusion 5. If the suture is removed after a certain interval (30 min, 1 h, or 2 h), reperfusion is achieved (transient MCAO); if the filament is left in place (24 h) the procedure is suitable as a model of permanent MCAO. This technique does not require craniectomy, a neurosurgical procedure to remove a portion of skull, which may affect intracranial pressure and temperature 6. It has become the most frequently used method to mimic permanent and transient focal cerebral ischemia in rats and mice 7,8. To evaluate the extent of cerebral infarction, we stain brain slices with 2,3,5-triphenyltetrazolium chloride (TTC) to identify ischemic brain tissue 9. In this video, we demonstrate the MCAO method and the determination of infarct size by TTC staining.

We demonstrate in the video a method for producing a middle cerebral artery occlusion in adult mice using an intraluminal monofilament. We also show how to evaluate the extent of cerebral infarction by 2,3,5-triphenyltetrazolium chloride (TTC) staining.

Stroke is the most common fatal neurological disease in the United States 1. The majority of strokes (88%) result from blockage of blood vessels in the ...

Medicine

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. The majority of all strokes result from an interruption in blood flow (ischemia) 1. Middle cerebral artery (MCA) delivers a great majority of blood to the lateral surface of the cortex 2, is the most common site of human stroke 3, and ischemia within its territory can result in extensive dysfunction or death 1,4,5. Survivors of ischemic stroke often suffer loss or disruption of motor capabilities, sensory deficits, and infarct. In an effort to capture these key characteristics of stroke, and thereby develop effective treatment, a great deal of emphasis is placed upon animal models of ischemia in MCA.
Here we present a method of permanently occluding a cortical surface blood vessel. We will present this method using an example of a relevant vessel occlusion that models the most common type, location, and outcome of human stroke, permanent middle cerebral artery occlusion (pMCAO). In this model, we surgically expose MCA in the adult rat and subsequently occlude via double ligature and transection of the vessel. This pMCAO blocks the proximal cortical branch of MCA, causing ischemia in all of MCA cortical territory, a large portion of the cortex. This method of occlusion can also be used to occlude more distal portions of cortical vessels in order to achieve more focal ischemia targeting a smaller region of cortex. The primary disadvantages of pMCAO are that the surgical procedure is somewhat invasive as a small craniotomy is required to access MCA, though this results in minimal tissue damage. The primary advantages of this model, however, are: the site of occlusion is well defined, the degree of blood flow reduction is consistent, functional and neurological impairment occurs rapidly, infarct size is consistent, and the high rate of survival allows for long-term chronic assessment.

Permanent Cerebral Vessel Occlusion via Double Ligature and Transection

We describe a highly reproducible method for the permanent occlusion of a rodent major cerebral blood vessel. This technique can be accomplished with very little peripheral damage, minimal blood loss, a high rate of long-term survival, and consistent infarct volume commensurate with the human clinical population.

Stroke is a leading cause of death, disability, and socioeconomic loss worldwide. The majority of all strokes result from an interruption in blood flow ...

Performing Permanent Distal Middle Cerebral with Common Carotid Artery Occlusion in Aged Rats to Study Cortical Ischemia with Sustained Disability

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, obesity and diabetes. Accordingly, when evaluating therapies for stroke in animals, it is important to select a model with excellent face validity. Ischemic stroke accounts for 80% of all strokes, and the majority of these occur in the territory of the middle cerebral artery (MCA), often inducing infarcts that affect the sensorimotor cortex, causing persistent plegia or paresis on the contralateral side of the body. We demonstrate in this video a method for producing ischemic stroke in elderly rats, which causes sustained sensorimotor disability and substantial cortical infarcts. Specifically, we induce permanent distal middle cerebral artery occlusion (MCAO) in elderly female rats by using diathermy forceps to occlude a short segment of this artery. The carotid artery on the ipsilateral side to the lesion was then permanently occluded and the contralateral carotid artery was transiently occluded for 60 min. We measure the infarct size using structural T2-weighted magnetic resonance imaging (MRI) at 24 hr and 8 weeks after stroke. In this study, the mean infarct volume was 4.5% &#177; 2.0% (standard deviation) of the ipsilateral hemisphere at 24 hr (corrected for brain swelling using Gerriet&#8217;s equation, n = 5). This model is feasible and clinically relevant as it permits the induction of sustained sensorimotor deficits, which is important for the elucidation of pathophysiological mechanisms and novel treatments.

Here we present a protocol to produce permanent distal middle cerebral artery occlusion in elderly female rats with simultaneous occlusion of the carotid arteries to generate large cortical infarcts and sustained deficits. We show confirmation of the lesion size using structural MRI at 24 hr and 8 weeks after stroke.

Stroke typically occurs in elderly people with a range of comorbidities including carotid (or other arterial) atherosclerosis, high blood pressure, ...

Surgical Approach for Middle Cerebral Artery Occlusion and Reperfusion Induced Stroke in Mice

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ischemic in origin and occur in the territory of the middle cerebral artery (MCA). Currently the only Food and Drug Administration (FDA) approved drug for the treatment of this devastating disease is tissue plasminogen activator (tPA). However, tPA has a small therapeutic window for administration (3 - 6 hr), and is only effective in 4% of the patients who actually receive it. Current research focuses on understanding the pathophysiology of stroke in order to find potential therapeutic targets. Thus, reliable models are crucial, and the MCA occlusion (MCAo) model (also termed the intraluminal filament or suture model) is deemed to be the most clinically relevant surgical model of ischemic stroke, and is fairly non-invasive and easily reproducible. Typically the MCAo model is used with rodents, especially with mice due to all the genetic variations available for this species. Here we describe (and present in the video) how to successfully perform the MCAo model (with reperfusion) in mice to generate reliable and reproducible data.

In order to understand the pathophysiology of stroke, it is important to use reliable models. This paper will describe one of the most frequently used stroke models in mice, termed the middle cerebral artery occlusion (MCAo) model (also termed the intraluminal filament or suture model) with reperfusion.

Stroke is a leading cause of death worldwide and continues to be one of the major causes of long-term adult disabilities. About 87% of strokes are ...

Low-intensity Blast Wave Model for Preclinical Assessment of Closed-head Mild Traumatic Brain Injury in Rodents

Traumatic brain injury (TBI) is a large-scale public health problem. Mild TBI is the most prevalent form of neurotrauma and accounts for a large number of medical visits in the United States. There are currently no FDA-approved treatments available for TBI. The increased incidence of military-related, blast-induced TBI further accentuates the urgent need for effective TBI treatments. Therefore, new preclinical TBI animal models that recapitulate aspects of human blast-related TBI will greatly advance the research efforts into the neurobiological and pathophysiological processes underlying mild to moderate TBI as well as the development of novel therapeutic strategies for TBI.
Here we present a reliable, reproducible model for the investigation of the molecular, cellular, and behavioral effects of mild to moderate blast-induced TBI. We describe a step-by-step protocol for closed-head, blast-induced mild TBI in rodents using a bench-top setup consisting of a gas-driven shock tube equipped with piezoelectric pressure sensors to ensure consistent test conditions. The benefits of the setup that we have established are its relative low-cost, ease of installation, ease of use and high-throughput capacity. Further advantages of this non-invasive TBI model include the scalability of the blast peak overpressure and the generation of controlled reproducible outcomes. The reproducibility and relevance of this TBI model has been evaluated in a number of downstream applications, including neurobiological, neuropathological, neurophysiological and behavioral analyses, supporting the use of this model for the characterization of processes underlying the etiology of mild to moderate TBI.

We present here a protocol of a blast wave model for rodents to investigate neurobiological and pathophysiological effects of mild to moderate traumatic brain injury. We established a gas-driven, bench-top setup equipped with pressure sensors allowing for reliable and reproducible generation of blast-induced mild to moderate traumatic brain injury.

Traumatic brain injury (TBI) is a large-scale public health problem. Mild TBI is the most prevalent form of neurotrauma and accounts for a large number of ...

Measuring Post-Stroke Cerebral Edema, Infarct Zone and Blood-Brain Barrier Breakdown in a Single Set of Rodent Brain Samples

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke involves middle cerebral artery occlusion (MCAO). Infarct zone, brain edema and blood-brain barrier (BBB) breakdown are measured as parameters that reflect the extent of brain injury after MCAO. A significant limitation to this method is that these measurements are normally obtained in different rat brain samples, leading to ethical and financial burdens due to the large number of rats that need to be euthanized for an appropriate sample size. Here we present a method to accurately assess brain injury following MCAO by measuring infarct zone, brain edema and BBB permeability in the same set of rat brains. This novel technique provides a more efficient way to evaluate the pathophysiology of stroke.

This protocol describes a novel technique of measuring the three most important parameters of ischemic brain injury on the same set of rodent brain samples. Using only one brain sample is highly advantageous in terms of ethical and economic costs.

One of the most common causes of morbidity and mortality worldwide is ischemic stroke. Historically, an animal model used to stimulate ischemic stroke ...

Middle Cerebral Artery Occlusion in Rats with Preserved Vascular Anatomy

A Rat Model of Middle Cerebral Artery Occlusion/Reperfusion Without Damaging the Anatomical Structure of Cerebral Vessels

Ischemic stroke stands as the primary cause of long-term disability and mortality among adults worldwide. Animal models of ischemic stroke have significantly contributed to our understanding of its pathological mechanisms and the development of potential treatments. Presently, there are two common methods involving filament (endovascular suture) techniques to induce animal models of cerebral ischemia. However, these methods have inherent limitations, such as reduced blood perfusion to the brain, damage to the external carotid artery system, impaired food and/or water intake, and sensory dysfunction of the face. This article introduces a new method for inducing a rat ischemic stroke model without compromising the cerebral vascular anatomy. In this study, the common carotid artery (CCA) of Sprague-Dawley rats was exposed, and an incision was made. A filament was then inserted through the incision into the internal carotid artery to occlude the middle cerebral artery. After 1.5 h of induced ischemia, the occluding filament was fully removed from both the internal carotid artery and the CCA. The incision in the CCA was subsequently sutured using 11-0 microsurgical sutures under a microscope (magnification 4x). Through the utilization of microsurgical techniques to repair the CCA, this study successfully developed a unique method to induce an ischemic stroke model in rats while preserving the anatomical integrity of cerebral blood vessels.

The current protocol describes a rat model of middle cerebral artery occlusion/reperfusion that preserves the anatomical structure of cerebral vessels without causing damage.

Ischemic stroke stands as the primary cause of long-term disability and mortality among adults worldwide. Animal models of ischemic stroke have ...

Shocktube Method to Model Highly Repetitive Low-Level Blast in Mice

Modeling Highly Repetitive Low-level Blast Exposure in Mice

Exposure to explosive blasts is a significant risk factor for brain trauma among exposed persons. Although the effects of large blasts on the brain are well understood, the effects of smaller blasts such as those that occur during military training are less understood. This small, low-level blast exposure also varies highly according to military occupation and training tempo, with some units experiencing few exposures over the course of several years whereas others experience hundreds within a few weeks. Animal models are an important tool in identifying both the injury mechanisms and long-term clinical health risks following low-level blast exposure. Models capable of recapitulating this wide range of exposures are necessary to inform acute and chronic injury outcomes across these disparate risk profiles.
Although outcomes following a few low-level blast exposures are easily modeled for mechanistic study, chronic exposures that occur over a career may be better modeled by blast injury paradigms with repeated exposures that occur frequently over weeks and months. Shown here are methods for modeling highly repetitive low-level blast exposure in mice. The procedures are based on established and widely used pneumatic shocktube models of open-field blast exposure that can be scaled to adjust the overpressure parameters and the number or interval of the exposures. These methods can then be used to either enable mechanistic investigations or recapitulate the routine blast exposures of clinical groups under study.

Author Spotlight: Deciphering the Long-Term Effects of Low-Level Blast Exposures in Mice

Presented here are methods for producing repeated low-intensity blast exposures using mice.

Exposure to explosive blasts is a significant risk factor for brain trauma among exposed persons. Although the effects of large blasts on the brain are ...

Custom Overpressure Air System for Inducing CNS Injuries in Murine Models

System for Focal, Closed-System Central Nervous System Injury

The prevalence of closed-system central nervous system (CNS) injuries underscores the need for an enhanced understanding of these traumas to improve protective and therapeutic interventions. Crucial to this research are animal models that replicate closed-system CNS injuries. In this context, a custom overpressure air system was engineered to reproduce a range of closed-system CNS injuries in murine models, including ocular, brain, and spinal cord trauma. To date, the system has been used to administer eye-, head-, or spine-directed overpressure air to model anteroposterior pole injury in the eye, indirect traumatic optic neuropathy (ITON), focal traumatic brain injury, and spinal cord injury. This paper provides a detailed protocol outlining the system&#39;s design and operation and shares representative results demonstrating its effectiveness. The robust framework presented here provides a strong foundation for ongoing research in CNS trauma. By leveraging the system&#8217;s flexible attributes, investigators can modify and carefully control the location, severity, and timing of injuries. This allows for comprehensive comparisons of molecular mechanisms and therapeutic efficacy across multiple closed-system CNS injuries.

Author Spotlight: Developing Precise and Clinically Relevant Models for Studying Secondary Degeneration in Traumatic Optic Neuropathy

This protocol describes a custom overpressure air system designed to induce closed-system central nervous system (CNS) injuries in mice, including ocular, brain, and spinal cord traumas. The goal of this protocol is to provide a framework for researchers to easily adapt and expand the system for their unique CNS trauma studies.

The prevalence of closed-system central nervous system (CNS) injuries underscores the need for an enhanced understanding of these traumas to improve ...

Effects of Blast-induced Neurotrauma on Pressurized Rodent Middle Cerebral Arteries

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