We thank all the members of the Christie Laboratory at the University of Victoria, past and present, for their contributions to the development of this protocol. This project was supported with funds from the Canadian Institutes for Health Research (CIHR: FRN 175042) and NSERC (RGPIN-06104-2019). The Figure 1 skull graphic was created with BioRender.

The authors have no conflicts of interest to disclose.

Most preclinical research has utilized models of mTBI that do not recapitulate the biomechanical forces seen in the clinical population. Here, it is shown how the ACHI model can be used to induce r-mTBIs in juvenile rats. This closed-headed model of r-mTBI has significant advantages over more invasive procedures. First, the ACHI does not normally cause skull fractures, brain bleeds, or fatalities, all of which would be contraindications of a &#34;mild&#34; TBI in clinical populations61. Second, th...

Traumatic brain injury (TBI) is a significant health issue, with ~2 million cases in Canada and the United States every year1,2. TBI affects all age groups and genders and has an incidence rate greater than any other disease, notably including breast cancer, AIDS, Parkinson&#39;s disease, and multiple sclerosis3. Despite the prevalence of TBI, its pathophysiology remains poorly understood, and treatment options are limited. In part, this is because 85% of all TBIs are classified as mild (mTBI), and mTBI has previously been thought to produce only limited and transient behavioral changes with no long-term neuropsychiatric consequences4,5. It is now recognized that mTBI recovery can take weeks to years5,6, precipitate more serious neurological conditions4, and that even repeated &#34;sub-concussive&#34; impacts affect the brain7. This is alarming as athletes in sports such as hockey/football have &#62;10 head sub-concussive impacts per game/practice session7,8,9,10.
Adolescents have the highest incidence of mTBI,&#160;and in Canada, roughly one in 10 teens will seek medical care for a sport-related concussion annually11,12. In reality, any sub-concussive head impact or mTBI can cause diffuse damage to the brain, and this could also create a more vulnerable state for subsequent injuries and/or more serious neurological conditions13,14,15,16,17. In Canada, it is recognized legally via Rowan&#39;s law that prior injury can increase the vulnerability of the brain to further injury18, but mechanistic understanding of r-mTBI remains woefully inadequate. It is clear, however, that single and r-mTBI can impact learning capacity during school years19,20, have sex-specific outcomes21,22,23,24, and impair cognitive capacity later in life16,25,26. Indeed, cohort analyses strongly associate r-mTBI early in life with dementia later on27,28. r-mTBI is also potentially associated with chronic traumatic encephalopathy (CTE), which is characterized by the accumulation of hyperphosphorylated tau protein and progressive cortical atrophy and precipitated by significant inflammation27,29,30,31. Although the links between r-mTBI and CTE are currently controversial32, this model will allow them to be explored in greater detail in a preclinical setting.
An mTBI is often described as an &#34;unseen injury,&#34; as it occurs within a closed skull and is difficult to detect even with modern imaging techniques33,34. An accurate experimental model of mTBI should adhere to two tenets. First, it should recapitulate the biomechanical forces normally observed in the clinical population35. Second, the model should induce heterogeneous behavioral outcomes, something that is also highly prevalent in clinical populations36,37,38. Currently, the majority of preclinical models tend to be more severe, involving craniotomy, stereotaxic head restraint, anesthesia, and controlled cortical impacts (CCI) that produce significant structural damage and more extensive behavioral deficits than normally observed clinically33. Another concern with many preclinical models of concussion that involve craniotomies is that this procedure itself creates inflammation in the brain, and this can exacerbate mTBI symptoms and neuropathology from any subsequent injury39,40. Anesthesia also introduces several complex confounds, including reducing inflammation41,42,43, modulating microglial function44, glutamate release45, Ca2+ entry through NMDA receptors46, intracranial pressure, and cerebral metabolism47. Anesthesia further introduces confounds by increasing blood-brain barrier (BBB) permeability, tau hyperphosphorylation, and corticosteroid levels, while reducing cognitive function48,49,50,51. Additionally, diffuse, closed-headed injuries represent the vast majority of clinical mTBIs52. They also allow one to better study the multitude of factors that can influence behavioral outcomes, including sex21, age53, inter-injury-interval15, severity54, and the number of injuries23.
The direction of the accelerative/decelerative forces (vertical or horizontal) is also an important consideration for behavioral and molecular outcomes. Research from Mychasiuk and colleagues have compared two models of diffuse closed-headed mTBI: weight-drop (vertical forces) and lateral impact (horizontal forces)55. Both the behavioral and molecular analyses revealed heterogeneous model- and sex-dependent outcomes following mTBI. Thus, animal models that help avoid surgical procedures, while incorporating linear and rotational forces, are more representative of the physiological conditions under which these injuries normally occur33,56. The ACHI model was created in response to this need, allowing for the rapid and reproducible induction of mTBI in rats while avoiding procedures (i.e., anesthesia) that are known to bias sex differences57.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D-printed helment&#160;</td>
			<td></td>
			<td></td>
			<td>Designed and constructed by Christie laboratory (See Specifications in Christie et al. (2019), Current Protocols in Neuroscience)&#160;</td>
		</tr>
		<tr>
			<td>Agarose&#160;</td>
			<td>Fisher Scientific (BioReagents)</td>
			<td>BP160500</td>
			<td></td>
		</tr>
		<tr>
			<td>Anesthesia chamber</td>
			<td>Home Made</td>
			<td>N/A</td>
			<td>Plexiglass Container</td>
		</tr>
		<tr>
			<td>Automatic Heater Controller</td>
			<td>Warner Electric</td>
			<td>TC-324B</td>
			<td></td>
		</tr>
		<tr>
			<td>Axon Digidata</td>
			<td>Molecular Devices</td>
			<td>1440A</td>
			<td>Low-noise Data Acquisition System</td>
		</tr>
		<tr>
			<td>Balance beam&#160;</td>
			<td></td>
			<td></td>
			<td>Can be constructed or purchased (100 cm long x 2 cm wide x 0.75 cm thick)</td>
		</tr>
		<tr>
			<td>Calcium Chloride</td>
			<td>Bio Basic Canada Inc.&#160;</td>
			<td>CD0050</td>
			<td>For aCSF</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Dage MTI</td>
			<td>NC-70</td>
			<td></td>
		</tr>
		<tr>
			<td>Carbogen tank</td>
			<td>Praxair</td>
			<td>MM OXCD5C-K</td>
			<td>Carbon Dioxide 5%, Oxygen 95%</td>
		</tr>
		<tr>
			<td>Clampex Software</td>
			<td>Molecular Devices</td>
			<td>Clampex 10.5 Version</td>
			<td></td>
		</tr>
		<tr>
			<td>Compresstome Vibrating Microtome</td>
			<td>Precisionary</td>
			<td>VF 310-0Z</td>
			<td></td>
		</tr>
		<tr>
			<td>Concentric Bipolar Electrode</td>
			<td>FHC Inc.</td>
			<td>CBAPC75</td>
			<td></td>
		</tr>
		<tr>
			<td>Dextrose (D-Glucose)</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>D16-3</td>
			<td>aCSF</td>
		</tr>
		<tr>
			<td>Digital Stimulus Isolation Amplifier&#160;&#160;</td>
			<td>Getting Instruments, Inc.&#160;</td>
			<td>Model 4D</td>
			<td></td>
		</tr>
		<tr>
			<td>Disodium Phosphate</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>S373-500</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td>Dissection Tools</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Feather Double Edge Blade</td>
			<td>Electron Microscopy Sciences</td>
			<td>72002-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter Paper</td>
			<td>Whatman 1</td>
			<td>1001-055</td>
			<td></td>
		</tr>
		<tr>
			<td>Flaming/Brown Micropipette Puller</td>
			<td>Sutter Instrument</td>
			<td>P-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Hair Claw Clip</td>
			<td></td>
			<td></td>
			<td>Can be obtained from any department store</td>
		</tr>
		<tr>
			<td>Home and Recovery Cages</td>
			<td></td>
			<td></td>
			<td>Normal rat cages from animal care unit.</td>
		</tr>
		<tr>
			<td>Hum Bug Noise Eliminator</td>
			<td>Quest Scientific&#160;</td>
			<td>726300</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane USP</td>
			<td>Fresenius Kabi</td>
			<td>CP0406V2</td>
			<td></td>
		</tr>
		<tr>
			<td>Isotemp 215 Digital Water Bath</td>
			<td>Fisher Scientific&#160;</td>
			<td>15-462-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Leica Impact One CCI unit</td>
			<td>Leica Biosystems</td>
			<td></td>
			<td>Tip is modified to hold 7mm rubber impact tip</td>
		</tr>
		<tr>
			<td>Long-Evans rats, male</td>
			<td colspan="3">Charles River Laboratories (St. Constant, PQ)</td>
		</tr>
		<tr>
			<td>Low-Density Foam Pad</td>
			<td></td>
			<td></td>
			<td>3&#34; polyurethane foam sheet&#160;</td>
		</tr>
		<tr>
			<td>Magnesium Chloride</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>M33-500</td>
			<td>aCSF</td>
		</tr>
		<tr>
			<td>Male Long Evans Rats</td>
			<td>Charles River Laboratories</td>
			<td></td>
			<td>Animals ordered from Charles River Laboratories, or pups bred at the University of Victoria</td>
		</tr>
		<tr>
			<td>MultiClamp 700B Amplifier</td>
			<td>Molecular Devices</td>
			<td>Model 700B</td>
			<td></td>
		</tr>
		<tr>
			<td>pH Test Strips</td>
			<td>VWR Chemicals BDH</td>
			<td>BDH83931.601</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium Chloride</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>P217-500</td>
			<td>aCSF, PBS</td>
		</tr>
		<tr>
			<td>Potassium Phosphate</td>
			<td>Sigma</td>
			<td>P9791-500G</td>
			<td>PBS</td>
		</tr>
		<tr>
			<td>Push Button Controller</td>
			<td>Siskiyou Corporation&#160;</td>
			<td>MC1000e</td>
			<td>Four-axis Closed Loop Controller Push-Button</td>
		</tr>
		<tr>
			<td>Sample Discs</td>
			<td>ELITechGroup</td>
			<td>SS-033</td>
			<td>For use with Vapor Pressure Osmometer</td>
		</tr>
		<tr>
			<td>Small towel</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium Bicarbonate</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>S233-500</td>
			<td>aCSF</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>S271-3</td>
			<td>For aCSF, PBS</td>
		</tr>
		<tr>
			<td>Sodium Phosphate</td>
			<td>Fisher Scientific (Chemical)</td>
			<td>S369-500</td>
			<td>aCSF</td>
		</tr>
		<tr>
			<td>Soft Plastic Restraint Cones</td>
			<td>Braintree Scientific</td>
			<td>model DC-200</td>
			<td></td>
		</tr>
		<tr>
			<td>Stopwatch</td>
			<td></td>
			<td></td>
			<td>Many lab members use their iPhone for this</td>
		</tr>
		<tr>
			<td>Table or large cart with raised edges&#160;</td>
			<td></td>
			<td></td>
			<td>For NAP and ACHI</td>
		</tr>
		<tr>
			<td>Thin Wall Borosilicate Glass (with Filament)</td>
			<td>Sutter Instrument</td>
			<td>BF150-110-10</td>
			<td>Outside diameter: 1.5 mm; Inside diameter: 1.10 mm; Length: 10 cm</td>
		</tr>
		<tr>
			<td>Upright Microscope</td>
			<td>Olympus</td>
			<td>Olympus BX5OWI</td>
			<td>5x MPlan 0.10 NA Objective lens</td>
		</tr>
		<tr>
			<td>Vapor Pressure Osmometer</td>
			<td>Vapro</td>
			<td>Model 5600</td>
			<td>aCSF should be 300-310 mOSM</td>
		</tr>
		<tr>
			<td>Vetbond Tissue Adhesive</td>
			<td>3M</td>
			<td>1469SB</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibraplane Vibration Isolation Table</td>
			<td>Kinetic Systems</td>
			<td>9101-01-45</td>
			<td></td>
		</tr>
	</tbody>
</table>

assessing changes in synaptic plasticity using an awake closed-head injury model of mild traumatic brain injury

Mild traumatic brain injuries (mTBIs) are a prevalent health issue in North America. There is increasing pressure to utilize ecologically valid models of closed-head mTBI in the preclinical setting to increase translatability to the clinical population. The awake closed-headed injury (ACHI) model uses a modified controlled cortical impactor to deliver closed-headed injury, inducing clinically relevant behavioral deficits without the need for a craniotomy or the use of an anesthetic.
This technique does not normally induce fatalities, skull fractures, or brain bleeds, and is more consistent with being a mild injury. Indeed, the mild nature of the ACHI procedure makes it ideal for studies investigating repetitive mTBI (r-mTBI). Growing evidence indicates that r-mTBI can result in a cumulative injury that produces behavioral symptoms, neuropathological changes, and neurodegeneration. r-mTBI is common in youths playing sports, and these injuries occur during a period of robust synaptic reorganization and myelination, making the younger population particularly vulnerable to the long-term influences of r-mTBI.
Further, r-mTBI occurs in cases of intimate partner violence, a condition for which there are few objective screening measures. In these experiments, synaptic function was assessed in the hippocampus in juvenile rats that had experienced r-mTBI using the ACHI model. Following the injuries, a tissue slicer was utilized to make hippocampal slices to evaluate bidirectional synaptic plasticity in the hippocampus at either 1 or 7 days following the r-mTBI. Overall, the ACHI model provides researchers with an ecologically valid model to study changes in synaptic plasticity following mTBI and r-mTBI.

The awake closed-head injury model is a viable method of inducing r-mTBI in juvenile rats. Rats exposed to r-mTBI with the ACHI model did not show overt behavioral deficits. Subjects in these experiments did not exhibit latency to right or apnea at any point during the r-mTBI procedure, indicating that this was indeed a mild TBI procedure. Subtle behavioral differences did emerge in the NAP; as described above, the rats were scored on four sensorimotor tasks (startle response, limb extension, beam walk, and rotating beam...

Watch this Scientific Journal Video about Assessing Changes in Synaptic Plasticity Using an Awake Closed-Head Injury Model of Mild Traumatic Brain Injury at JoVE.com

Assessing Changes in Synaptic Plasticity Using an Awake Closed-Head Injury Model of Mild Traumatic Brain Injury

Here, it is demonstrated how an awake closed-head injury model can be used for examining the effects of repeated mild traumatic brain injury (r-mTBI) on synaptic plasticity in the hippocampus. The model replicates important features of r-mTBI in patients and is used in conjunction with in vitro electrophysiology.

Mild traumatic brain injuries (mTBIs) are a prevalent health issue in North America. There is increasing pressure to utilize ecologically valid models of ...

assessing-changes-synaptic-plasticity-using-an-awake-closed-head

Research

JoVE Journal

Neuroscience

2.2K Views.  University of Victoria. Here, it is demonstrated how an awake closed-head injury model can be used for examining the effects of repeated mild traumatic brain injury (r-mTBI) on synaptic plasticity in the hippocampus. The model replicates important features of r-mTBI in patients and is used in conjunction with in vitro electrophysiology.

Video: Assessing Changes in Synaptic Plasticity Using an Awake Closed-Head Injury Model of Mild Traumatic Brain Injury

Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair.
Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed skull 18. Among the TBI models, LFP is the most established and commonly used model to evaluate mixed focal and diffuse brain injury 19. It is reproducible and is standardized to allow for the manipulation of injury parameters. LFP recapitulates injuries observed in humans, thus rendering it clinically relevant, and allows for exploration of novel therapeutics for clinical translation 20.
We describe the detailed protocol to perform LFP procedure in mice. The injury inflicted is mild to moderate, with brain regions such as cortex, hippocampus and corpus callosum being most vulnerable. Hippocampal and motor learning tasks are explored following LFP.

Lateral fluid percussion (LFP), an established model of traumatic brain injury in mice, is demonstrated. LFP fulfills three major criteria for animal models: validity, reliability and clinical relevance. The procedure, consisting of surgical craniotomy, fixation of hub followed by induction of injury, resulting in focal and diffuse injuries, is described.

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and ...

Investigations on Alterations of Hippocampal Circuit Function Following Mild Traumatic Brain Injury

Traumatic Brain Injury (TBI) afflicts more than 1.7 million people in the United States each year and even mild TBI can lead to persistent neurological impairments 1. Two pervasive and disabling symptoms experienced by TBI survivors, memory deficits and a reduction in seizure threshold, are thought to be mediated by TBI-induced hippocampal dysfunction 2,3. In order to demonstrate how altered hippocampal circuit function adversely affects behavior after TBI in mice, we employ lateral fluid percussion injury, a commonly used animal model of TBI that recreates many features of human TBI including neuronal cell loss, gliosis, and ionic perturbation 4-6.
	Here we demonstrate a combinatorial method for investigating TBI-induced hippocampal dysfunction. Our approach incorporates multiple ex vivo physiological techniques together with animal behavior and biochemical analysis, in order to analyze post-TBI changes in the hippocampus. We begin with the experimental injury paradigm along with behavioral analysis to assess cognitive disability following TBI. Next, we feature three distinct ex vivo recording techniques: extracellular field potential recording, visualized whole-cell patch-clamping, and voltage sensitive dye recording. Finally, we demonstrate a method for regionally dissecting subregions of the hippocampus that can be useful for detailed analysis of neurochemical and metabolic alterations post-TBI.
	These methods have been used to examine the alterations in hippocampal circuitry following TBI and to probe the opposing changes in network circuit function that occur in the dentate gyrus and CA1 subregions of the hippocampus (see Figure 1). The ability to analyze the post-TBI changes in each subregion is essential to understanding the underlying mechanisms contributing to TBI-induced behavioral and cognitive deficits. 
	The multi-faceted system outlined here allows investigators to push past characterization of phenomenology induced by a disease state (in this case TBI) and determine the mechanisms responsible for the observed pathology associated with TBI.

A multi-faceted approach to investigating functional changes to hippocampal circuitry is explained. Electrophysiological techniques are described along with the injury protocol, behavioral testing and regional dissection method. The combination of these techniques can be applied in similar fashion for other brain regions and scientific questions.

Traumatic Brain Injury (TBI) afflicts more than 1.7 million people in the United States each year and even mild TBI can lead to persistent neurological ...

A Method to Inflict Closed Head Traumatic Brain Injury in Drosophila

Traumatic brain injury (TBI) affects millions of people each year, causing impairment of physical, cognitive, and behavioral functions and death. Studies using Drosophila have contributed important breakthroughs in understanding neurological processes. Thus, with the goal of understanding the cellular and molecular basis of TBI pathologies in humans, we developed the High Impact Trauma (HIT) device to inflict closed head TBI in flies. Flies subjected to the HIT device display phenotypes consistent with human TBI such as temporary incapacitation and progressive neurodegeneration. The HIT device uses a spring-based mechanism to propel flies against the wall of a vial, causing mechanical damage to the fly brain. The device is inexpensive and easy to construct, its operation is simple and rapid, and it produces reproducible results. Consequently, the HIT device can be combined with existing experimental tools and techniques for flies to address fundamental questions about TBI that can lead to the development of diagnostics and treatments for TBI. In particular, the HIT device can be used to perform large-scale genetic screens to understand the genetic basis of TBI pathologies.

A Method to Inflict Closed Head Traumatic Brain Injury in Drosophila

Here we describe a method to inflict closed head traumatic brain injury (TBI) in Drosophila. This method provides a gateway to investigate the cellular and molecular mechanisms that underlie TBI pathologies using the vast array of experimental tools and techniques available for flies.

Traumatic brain injury (TBI) affects millions of people each year, causing impairment of physical, cognitive, and behavioral functions and death. Studies ...

Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is the most common type of acquired brain injury. Since patients with traumatic brain injury show a tremendous variability and heterogeneity (age, gender, type of trauma, other possible pathologies, etc.), animal models play a key role in unraveling factors that are limitations in clinical research. They provide a standardized and controlled setting to investigate the biological mechanisms of injury and repair following TBI. However, not all animal models mimic the diffuse and subtle nature of mTBI effectively. For example, the commonly used controlled cortical impact (CCI) and lateral fluid percussion injury (LFPI) models make use of a craniotomy to expose the brain and induce widespread focal trauma, which are not commonly seen in mTBI. Therefore, these experimental models are not valid to mimic mTBI. Thus, an appropriate model should be used to investigate mTBI. The Marmarou weight drop model for rats induces similar microstructural alterations and cognitive impairments as seen in patients who sustain mild trauma; therefore, this model was selected for this protocol. Conventional computed tomography and magnetic resonance imaging (MRI) scans commonly show no damage following a mild injury, because mTBI induces often only subtle and diffuse injuries. With diffusion weighted MRI, it is possible to investigate microstructural properties of brain tissue, which can provide more insight into the microscopic alterations following mild trauma. Therefore, the goal of this study is to obtain quantitative information of a selected region-of-interest (i.e., hippocampus) to follow up disease progression after obtaining a mild and diffuse brain injury.

The overall goal of this procedure is to obtain quantitative microstructural information of the hippocampus in a rat with mild traumatic brain injury. This is done using an advanced diffusion-weighted magnetic resonance imaging protocol and region-of-interest based analysis of parametric diffusion maps.

Mild traumatic brain injury (mTBI) is the most common type of acquired brain injury. Since patients with traumatic brain injury show a tremendous ...

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 ...

Electromagnetic Controlled Closed-Head Model of Mild Traumatic Brain Injury in Mice

Highly reproducible animal models of traumatic brain injury (TBI), with well-defined pathologies, are needed for testing therapeutic interventions and understanding the mechanisms of how a TBI alters brain function. The availability of multiple animal models of TBI is necessary to model the different aspects and severities of TBI seen in people. This manuscript describes the use of a midline closed head injury (CHI) to develop a mouse model of mild TBI. The model is considered mild because it does not produce structural brain lesions based on neuroimaging or gross neuronal loss. However, a single impact creates enough pathology that cognitive impairment is measurable at least 1 month after injury. A step-by-step protocol to induce a CHI in mice using a stereotaxically guided electromagnetic impactor is defined in the paper. The benefits of the mild midline CHI model include the reproducibility of the injury-induced changes with low mortality. The model has been temporally characterized up to 1 year after the injury for neuroimaging, neurochemical, neuropathological, and behavioral changes. The model is complementary to open skull models of controlled cortical impact using the same impactor device. Thus, labs can model both mild diffuse TBI and focal moderate-to-severe TBI with the same impactor.

The protocol describes mild traumatic brain injury in a mouse model. In particular, a step-by-step protocol to induce a mild midline closed head injury and the characterization of the animal model is fully explained.

Highly reproducible animal models of traumatic brain injury (TBI), with well-defined pathologies, are needed for testing therapeutic interventions and ...

Validating Injury Response and Behavioral Assessments in an mTBI Rat Model

Rat Model of Closed-Head Mild Traumatic Injury and its Validation

Animal models are crucial for advancing our understanding of mild traumatic brain injury (mTBI) and guiding clinical research. To achieve meaningful insights, developing a stable and reproducible animal model is essential. In this study, we report a detailed description of a closed-head mTBI model and a representative validation method using Sprague-Dawley rats to verify the modeling effect. The model involves dropping a 550 g mass weight from a height of 100 cm directly onto the head of a rat on a destructible surface, followed by a 180-degree turn. To assess the injury, rats underwent a series of neurobehavioral assessments 10 min post-injury, including time of loss of consciousness, first seeking-behavior time, escape ability, and beam balance ability test. During the acute and subacute stages following the injury, behavioral tests were conducted to assess motor coordination ability (Beam task), anxiety (Open Field test), and learning and memory abilities (Morris Water Maze test). The closed-head mTBI model produced a consistent injury response with minimal mortality and replicated real-life situations. The validation method effectively verified the model development and ensured the stability and consistency of the model.

Author Spotlight: Advancing Traumatic Brain Injury Research - A Closed-Head Model for Accurate Replication and Rapid Assessment 

Here, we present a closed-head mild traumatic brain injury (mTBI) rat model and its validation exhibiting remarkable similarity to human mTBI concerning behavioral manifestations during the acute and subacute stages.

Animal models are crucial for advancing our understanding of mild traumatic brain injury (mTBI) and guiding clinical research. To achieve meaningful ...

rmTBI Induction in Mice via a Closed-Head Injury Method

Modified Mouse Model of Repetitive Mild Traumatic Brain Injury Incorporating Thinned-Skull Window and Fluid Percussion

Mild traumatic brain injury is a clinically highly heterogeneous neurological disorder. Highly reproducible traumatic brain injury (TBI) animal models with well-defined pathologies are urgently needed for studying the mechanisms of neuropathology after mild TBI and testing therapeutics. Replicating the entire sequelae of TBI in animal models has proven to be a challenge. Therefore, the availability of multiple animal models of TBI is necessary to account for the diverse aspects and severities seen in TBI patients. CHI is one of the most common methods for fabricating rodent models of rmTBI. However, this method is susceptible to many factors, including the impact method used, the thickness and shape of the skull bone, animal apnea, and the type of head support and immobilization utilized. The aim of this protocol is to demonstrate a combination of the thinned-skull window and fluid percussion injury (FPI) methods to produce a precise mouse model of CHI-associated rmTBI. The primary objective of this protocol is to minimize factors that could impact the accuracy and consistency of CHI and FPI modeling, including skull bone thickness, shape, and head support. By utilizing a thinned-skull window method, potential inflammation due to craniotomy and FPI is minimized, resulting in an improved mouse model that replicates the clinical features observed in patients with mild TBI. Results from behavior and histological analysis using hematoxylin and eosin (HE) staining suggest that rmTBI can lead to a cumulative injury that produces changes in both behavior and gross morphology of the brain. Overall, the modified CHI-associated rmTBI presents a useful tool for researchers to explore the underlying mechanisms that contribute to focal and diffuse pathophysiological changes in rmTBI.

Author Spotlight: Optimizing Rodent Models for Investigating the Mechanisms and Rehabilitation in Repeated Mild Traumatic Brain Injury

This protocol presents a modified mouse model of repetitive mild traumatic brain injury (rmTBI) induced via a closed-head injury (CHI) method. The approach features a thinned-skull window and fluid percussion to reduce the inflammation commonly caused by meninges exposure, along with improved reproducibility and accuracy in modeling rmTBI in rodents.

Mild traumatic brain injury is a clinically highly heterogeneous neurological disorder. Highly reproducible traumatic brain injury (TBI) animal models ...

Fluorescent Dye-Based Visualization of Blood-Brain Barrier Breakdown in Mice

Evaluation of Blood-Brain Barrier Breakdown in a Mouse Model of Mild Traumatic Brain Injury

Fluorescent dyes are used to determine the extent of dye extravasation that occurs due to blood-brain barrier (BBB) breakdown. Labeling with these dyes is a complex process influenced by several factors, such as the concentration of dyes in the blood, permeability of brain vessels, duration of dye extravasation, and reduction in dye concentration in the tissue due to degradation and diffusion. In a mild traumatic brain injury model, exposure to blast-induced shock waves (BSWs) triggers BBB breakdown within a limited time window. To determine the precise sequence of BBB breakdown, Evans blue, and fluorescein isothiocyanate-dextran were injected intravascularly and intracardially into mice at various time points relative to BSW exposure. The distribution of dye fluorescence in brain slices was then recorded. Differences in the distribution and intensity between the two dyes revealed the spatiotemporal sequence of BBB breakdown. Immunostaining of the brain slices showed that astrocytic and microglial responses correlated with the sites of BBB breakdown. This protocol has broad potential for application in studies involving different BBB breakdown models.

A method was developed to visualize dye extravasation due to blood-brain barrier (BBB) breakdown by administering two fluorescent dyes to mice at different time points. The use of glycerol as a cryoprotectant facilitated immunohistochemistry on the same sample.

Fluorescent dyes are used to determine the extent of dye extravasation that occurs due to blood-brain barrier (BBB) breakdown. Labeling with these dyes is ...