The author is grateful for the assistance of Mrs. Sharon Spana (University of Sydney) in rodent monitoring, handling and experimentation. The authorwould like to thank Prof. Jonathan Stone and Dr. Dan Johnstone for the assistance in the preparation of this manuscript. PhD funding support has been provided by University of Sydney and Australian Center for Excellence in Vision.

Ethics statement: The protocol follows the animal care guidelines of University of Sydney, AEC #5657. Anaesthesia was approved by animal ethics committee (University of Sydney, AEC #5657).
1. Equipment Preparation
<ol>
	<li>Use real time skin temperature tracking. Switch on computer, and data acquisition hardware.</li>
	<li>Open temperature recording software and adjust temperature setting to between 30-35 &#176;C and the frequency of sampling to every 100 msec.</li>
	<li>Optional: Insert rectal thermometer to ensure core temperature remains stable at 37.5 &#176;C.</li>
</ol>
2. Calibration of the Manual Sphygmomanometer
<ol>
	<li>Connect neonatal arm cuff to sphygmomanometer.Use a size 2 cuff for a 250-550 g rat. An adaptor may be necessary to connect the cuff tubing to the sphygmomanometer.</li>
	<li>Deflate the cuff by either loosening the air release valve or disconnecting the cuff tubing from the adaptor. Ensure no pressure remains in the tubing and the manometer needle rests at zero inside the oval/rectangle.</li>
	<li>Check the pressure between tubing, manometer and cuff. Inflate the cuff with gentle pumps of the inflation bulb until it reads 100 mmHg on the manometer. Ensure the pressure remains constant. Deflate the cuff by slowly opening the air release value.</li>
</ol>
3. Animal Preparation
Note: Animals that are to undergo light injury require dark adaption the night before remote ischemia. Animals undergoing light damage require dark rearing (12 hr light:dark cycle (5 lux))
<ol>
	<li>Perform remote ischemia in either awake or anesthetised rodents. Ensure that animals have a healthy muscle tone. Ensure this by pinching the upper hind limb to confirm there is adequate muscle present. RIP-induced protection against light injury has been tested in sedentary rats up to 6 months of age.</li>
	<li>Anesthetised preparation for RIP
	<ol>
		<li>Inject rats with an intraperitoneal injection of 60 mg/kg ketamine and 5 mg/kg xylazine. Check the depth of anaesthesia by extending the leg and pinching the skin on the underside of the foot. The animal has no reflex if it is deeply anesthetised. Apply artificial tears to avoid corneal dryness whilst under anaesthesia.</li>
		<li>Place rats on either a heat pad or circulating water heater tubing to maintain a constant body temperature of 37.5 &#176;C. Position the rat in the prone position with the lower limbs&#8217; foot pads facing up. Either the right or left limb may undergo remote ischemia.</li>
	</ol>
	</li>
	<li>Awake preparation for RIP Note: Awake animal experimentation requires two people. One person restrains the animal and the second person operates the manual&#160;sphygmomanometer. The experimenters must be confident to perform the procedure as restraint increases the risk of injury to handlers. The rats undergoing remote ischemia must be conditioned to manual restraint. Depending on intuitional guidelines manual restraint should be progress from 30 sEC to a maximum of 5 min&#160;over a number of weeks. Timid animals that fail to acclimatise to manual restraint should be excluded from awake experimentation. Lastly, manual restraint is likely to cause stress (and potentially introduce confounds to the study) to animals and a sham cohort (placement of cuff without inflammation) must be used to accurately interpret RIP study results.
	<ol>
		<li>Cut a towel into a 15 cm x 30-50 cm piece and place the short edge perpendicular to the rat&#8217;s spine, covering the head to the top of the hind limbs.</li>
		<li>Tuck the short edge under the rat&#8217;s torso tightly and begin to wrap the rat with the remaining long edge of towel. Secure the wrapped animal under the arm in a supine position. If the rat is held under the left arm, free the rat&#8217;s right limb from the towel.</li>
	</ol>
	</li>
</ol>
4. Application of Skin Temperature Probe
<ol>
	<li>Extend the leg of the rat which is to undergo ischemia and place the skin probe on the footpad. Position the skin probe to maximise contact between the temperature probe and the skin. Firmly push the probe into the footpad and affix the probe with paper tape.</li>
	<li>Check the skin probe placement by tracking the temperature on temperature recording software. Ensure that the skin temperature is between 30-34 &#176;C and remains stable. Track the skin temperature for 1-2 min. Adjust the skin probe if the temperature is unstable or below 30 &#176;C.</li>
</ol>
5. Remote Ischemia
<ol>
	<li>Deflate the cuff and ensure the air pressure valve is closed. Extend the leg and loosely encircle the cuff on the upper hind limb. Use the forefinger and thumb to extend the leg and the lower digits to keep the loosened cuff in position.</li>
	<li>Raise the anesthetised animal&#8217;s cuff pressure to 160 mmHg, and in awake animals increase the cuff pressure to 180 mmHg. 
	Note: The anesthetised blood pressure of rats ranges from 120-140 mmHg and rises to 160 mmHg when conscious. Commence the timer and foot temperature recordings once the correct pressure is reached. 
	Note: The foot temperature should drop by 2 &#176;C after 5 min of constant pressure.</li>
	<li>Maintain the position of the cuff above the animal&#8217;s &#8220;knee&#8221; throughout the ischemia. Cuff pressure will begin to drop after a few minutes, or if the rat&#8217;s limb is moving.</li>
	<li>Repeatedly pump the inflation bulb in short bursts to maintain the desired cuff pressure repetitive short burst of pumping</li>
	<li>Remote ischemia can be delivered continuously for between 5 and 15 min. The ischemia reperfusion protocol includes 2 periods of 5 min ischemia with an intervening 5 min reperfusion.</li>
	<li>Deflate the cuff pressure by loosening the air pressure valve. Check the temperature change over the course of the ischemia protocol. Release the cuff.</li>
	<li>Continue with injury experimentation. Animals under the effect of anaesthesia will need to be placed on a heat pad. Continue to monitor animals until ambulatory. Animals cannot be returned to housing until walking.</li>
</ol>
6. Light Injury - Retinal Degeneration Model
<ol>
	<li>Dark adapt the animals overnight (12-15 hr). Immediately following remote ischemia conditioning or sham remote ischemia (animal restraint) place animals in Perspex housing with food and water.</li>
	<li>Switch on fluorescent lighting (1,000 lux) located above Perspex housing at 9 am for 24 hr.&#160;Following light exposure, return the animals to dim cyclic lighting for 7 days. </li>
</ol>
7. Post-remote Ischemia Procedures
<ol>
	<li>Vision assessment with Electroretinogram (ERG): 
	Note: The ERG set-up and flash protocol followed Brandli and Stone26.
	<ol>
		<li>Dark adapt animals overnight (12-15 hr). Under dim red illumination anesthetize the animals by intraperitoneal injection of ketamine and xylazine (60 mg/kg and 5 mg/kg, respectively). Mydriatic (atropine sulphate 1.0%), corneal anaesthetic (proxymetacaine 0.5%).</li>
		<li>Apply corneal hydration (Carbomer polymer) eye drops immediately to the cornea. Apply eye gel at 20 min intervals to maintain corneal hydration.</li>
		<li>Draw a loosely tied thread around the eyeball to aid stable ERG recordings. Monitor temperature using a rectal probe and maintain animal&#8217;s body temperature at 37-37.5 &#176;C.</li>
		<li>Position the head inside a Ganzfeld integrating sphere. 
		Note: The Ganzfeld is a fully programmable light stimulus that delivers uniform whit flashes from LEDs to the eye.</li>
		<li>Record the electroretinogram using a custom-made 4 mm platinum positive electrode lightly touching the cornea and a 2 mm diameter Ag/AgCl pellet electrode inserted into the mouth. Reference both electrodes to a stainless steel needle inserted subcutaneously into the rump.</li>
		<li>Record signals with band-pass setting of 0.3-1,000 Hz (-3 dB), with a 2 kHz acquisition rate (AD Instruments). After a stable ERG recording is established subject the animal to a 10 min dark adaptation before commencing recordings.</li>
		<li>Follow the flash protocol as previously described by Brandli and Stone26.
		<ol>
			<li>Program the duration of the flash (we used flashes 1-2 msec in duration), and set its intensity to -4.4 to 2.0 log scot cd.s.m-2. Use bright flashes (2.0 log scot cd.s.m-2, 1 ms) to measure the retinal function. In this study it is the comparison between control, light injury and light injury with RIP.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>
8. TUNEL Assay
<ol>
	<li>Euthanize animals by intraperitoneal injection of phenobarbital overdose (100 mg/kg). Enucleate the eyes and fix in 4% paraformaldehyde.</li>
	<li>Wash the eyes in PBS before cyroprotecting eyes overnight in sucrose 30% (w/v). Embed the eyes in OCT compound and cut into 20 &#181;m sagittal sections using a cryostat.</li>
	<li>Perform the TUNEL assay on retinal sections with DAPI staining following the protocol of Maslim et al.27</li>
	<li>Use fluorescence microscopy for TUNEL counts of the retina. TUNEL cells were recorded from the outer nuclear layer (ONL); the outermost layer of the retina which contains photoreceptor nuclei. In this study, TUNEL counts were made in triplicate for each eye, with 5 eyes for each treatment group.</li>
	<li>Use one-way ANOVA to statistical compare group means of control, light injury, and light injury + RIP rats.</li>
</ol>

The author has nothing to disclose.

Rodent hind limb ischemia was successfully induced with a manual sphygmomanometer and cuff delivering neuroprotection to the photoreceptors of the retina. A finding consistent with ischemic conditioning induced protection of photoreceptors from light injury9,28.
Essentially, remote ischemia causes brief oxygen deprivation to tissues. Hence, remote ischemic preconditioning has many similarities to ischemic conditioning or alternatively termed ischemic tolerance, hypoxic preconditioni...

The survival of most, perhaps all, tissues in the face of metabolic stress can be improved by prior conditioning with a period of sublethal ischemia1,2. Ischemic preconditioning (IP) in practical terms is the exposure of tissue to sublethal ischemia, before the tissue experiences more severe stressors, such as a subsequent ischemic insult. In animal models, IP provides striking protection to the brain, retina, heart and lungs3-6. Correspondingly, observations in stroke patients showed a link between previous transient ischemic attacks and better clinical outcomes7,8. IP also protects retinal photoreceptors from non-ischemic injuries9.
The effectiveness of IP in diverse tissues and injuries suggests that it is activating an innate mechanism of cell survival present in all tissue. Ischemic preconditioning of the myocardium has been suggested to have protective effects through the upregulation of hypoxia inducible factor (HIF), known to regulate many metabolic pathways through the release of adenosine or through the opening of mitochondrial ATP potassium channels10,11. Adenosine release and ATP potassium channels are implicated in cerebral ischemia but, investigations into the neuroprotective mechanisms of ischemic conditioning to date have been focused on modifications to anti-excitotoxicity, anti-apoptotic and anti-inflammatory pathways12,13. Overall, understanding of the molecular process of ischemic conditioning for protecting neurons is limited.
Remote ischemic preconditioning attempts to condition distant critically important organs (heart, brain, lung) by generating ischemia in less critical tissues. Remote ischemic preconditioning (RIP) using the hind limb has been demonstrated to be neuroprotective in rodent models of stroke14-17. The method described by us provides a simple, reliable and non-invasive protocol for inducing RIP.
The vast majority of RIP protocols involve the hind limb, presumably because the femoral artery located in the upper hind limb can be easily identified and accessed for surgical clamping and tourniquet application. In invasive limb ischemic studies for the study of brain and skin protection, ischemia is induced by separating the femoral artery from the groin ligaments and clamping the femoral artery2,15,18.
The ischemia resulting from either limb cuffing or femoral artery clamping has been confirmed by changes at the limb including a loss of pulse, decrease in oxygenation and a drop in skin temperature. Remote ischemia can be confirmed by the loss of pulse by using laser Doppler or ultrasound Doppler17-19. Skin temperature can be used as alternative to Doppler although the relationship is non-linear20,21. Accurate temperature recordings are commonplace in laboratories and can be easily incorporated into remote ischemic studies.
An alternative to femoral clamping surgery is the induction of ischemia using a tourniquet. Tourniquet application produces comparable ischemia to that achieved with vessel clamping; Kutchner et al. compared invasive femoral artery clamping to a non-invasive tourniquet and found both methods halted blood flow to the limb and reduced skin damage in a plastic surgery model of skin flap ischemia18. Cuffing either the leg or arm and raising the cuff pressure to above systolic blood pressure has been found to be protective against ischemic damage in pigs and humans17,19,22.
Different tourniquet approaches to inducing remote ischemic include the use of a blood pressure cuff or an elastic band17,22,23. However, the use of an elastic band to induce ischemia is an unsafe method, potentially giving rise to an unregulated amount of pressure in the limb, with pressure rises above 500 mmHg being recorded in humans24. Further, limb ischemia using an elastic band leads to muscle damage in rats following the removal of the band23, as assessed by Evans Blue Dye, an in vivo marker of myofiber permeability25. In contrast, delivery of a controlled pressure to the tourniquet can be achieved using a blood pressure cuff connected to a sphygmomanometer17,19,22,26.
In this study, a light injury model of photoreceptor degeneration was used to demonstrate the neuroprotective efficacy of remote ischemic preconditioning. Remote ischemia was induced immediately before light injury, and prevented subsequent photoreceptor degeneration as confirmed by retinal function testing. The accompanying video will demonstrate the application of non-invasive remote ischemia.

<table><tbody><tr><td>Gold series DuraShock hand aneroid sphygmomanometer</td><td>Welch Allyn</td><td>DS56</td><td>Manual Sphygmomanometer</td></tr><tr><td>Neonate [size 2] 1 tube, 10 pack</td><td>Welch Allyn</td><td>5082-102-1</td><td>Limb blood pressure cuff</td></tr><tr><td>Luer lock adaptor</td><td>Welch Allyn</td><td>5082-178</td><td>Adaptor for neonatal cuff</td></tr><tr><td>Thermistor pod</td><td>AD Instruments</td><td>ML 309</td><td>skin tempertature unit</td></tr><tr><td>Skin temperture probe</td><td>AD Instruments</td><td>MLT 422/A</td><td></td></tr><tr><td>Powerlab, 4 channel acquistion hardware</td><td>AD Instruments</td><td>PL 35044</td><td></td></tr><tr><td>Homeothermic blanket system with flexible probe</td><td>Harvard Appartus</td><td>507222F</td><td></td></tr><tr><td>Towel</td><td></td><td></td><td>optional: awake remote ischemia</td></tr><tr><td>Isoflo - 100% Isoflurane (250 ml)</td><td>Abbot Animal Health</td><td>05260-05</td><td>optional: inhaltion anaesthetic remote ischemia</td></tr><tr><td>Ketamil - ketamine 100 mg/ml (50 ml)</td><td>Troy Laboratories Pty Ltd</td><td></td><td>optional: injectable anaesthetic remote ischemia</td></tr><tr><td>Xylium - Xylazine 100 mg/ml (50 ml)</td><td>Troy Laboratories Pty Ltd</td><td></td><td>optional: injectable anaesthetic remote ischemia</td></tr></tbody></table>

remote limb ischemic preconditioning:  a neuroprotective technique in rodents

Sublethal ischemia protects tissues against subsequent, more severe ischemia through the upregulation of endogenous mechanisms in the affected tissue. Sublethal ischemia has also been shown to upregulate protective mechanisms in remote tissues. A brief period of ischemia (5-10 min) in the hind limb of mammals induces self-protective responses in the brain, lung, heart and retina. The effect is known as remote ischemic preconditioning (RIP). It is a therapeutically promising way of protecting vital organs, and is already under clinical trials for heart and brain injuries. This publication demonstrates a controlled, minimally invasive method of making a limb &#8211; specifically the hind limb of a rat &#8211; ischemic. A blood pressure cuff developed for use in human neonates is connected to a manual sphygmomanometer and used to apply 160 mmHg pressure around the upper part of the hind limb. A probe designed to detect skin temperature is used to verify the ischemia, by recording the drop in skin temperature caused by pressure-induced occlusion of the leg arteries, and the rise in temperature which follows release of the cuff. This method of RIP affords protection to the rat retina against bright light-induced damage and degeneration.

A blood pressure cuff elevated to above 160 mmHg halts blood flow to the hind limb as seen clearly in Figure 1B. The lack of tissue oxygenation resulted in a reducing the animal&#8217;s foot temperature for an ischemia-reperfusion protocol (Figure 2). The foot temperature (33 &#176;C) was lower than core temperature and reliably reduced during cuff pressure elevation (31 &#176;C) rising when the cuff was deflated (32 &#176;C). A single 1,000 lux light injury was delivered to dim raised a...

Watch this Scientific Journal Video about Remote Limb Ischemic Preconditioning:  A Neuroprotective Technique in Rodents at JoVE.com

Remote Limb Ischemic Preconditioning:  A Neuroprotective Technique in Rodents

Remote ischemic preconditioning (RIP) is a method of conditioning tissues against damaging stress. We have established a method of remote ischemia at the hind limb, by inflating a sphygmomanometer cuff for 5-10 min. The neuroprotective capabilities of RIP have been demonstrated in a model of retinal degeneration in rodents.

Sublethal ischemia protects tissues against subsequent, more severe ischemia through the upregulation of endogenous mechanisms in the affected tissue. ...

remote-limb-ischemic-preconditioning-neuroprotective-technique

Research

JoVE Journal

Medicine

11.0K Views.  University of Sydney. Remote ischemic preconditioning (RIP) is a method of conditioning tissues against damaging stress. We have established a method of remote ischemia at the hind limb, by inflating a sphygmomanometer cuff for 5-10 min. The neuroprotective capabilities of RIP have been demonstrated in a model of retinal degeneration in rodents.

Video: Remote Limb Ischemic Preconditioning:  A Neuroprotective Technique in Rodents

Strategies for Study of Neuroprotection from Cold-preconditioning

Neurological injury is a frequent cause of morbidity and mortality from general anesthesia and related surgical procedures that could be alleviated by development of effective, easy to administer and safe preconditioning treatments. We seek to define the neural immune signaling responsible for cold-preconditioning as means to identify novel targets for therapeutics development to protect brain before injury onset. Low-level pro-inflammatory mediator signaling changes over time are essential for cold-preconditioning neuroprotection. This signaling is consistent with the basic tenets of physiological conditioning hormesis, which require that irritative stimuli reach a threshold magnitude with sufficient time for adaptation to the stimuli for protection to become evident.
Accordingly, delineation of the immune signaling involved in cold-preconditioning neuroprotection requires that biological systems and experimental manipulations plus technical capacities are highly reproducible and sensitive. Our approach is to use hippocampal slice cultures as an in vitro model that closely reflects their in vivo counterparts with multi-synaptic neural networks influenced by mature and quiescent macroglia / microglia. This glial state is particularly important for microglia since they are the principal source of cytokines, which are operative in the femtomolar range. Also, slice cultures can be maintained in vitro for several weeks, which is sufficient time to evoke activating stimuli and assess adaptive responses. Finally, environmental conditions can be accurately controlled using slice cultures so that cytokine signaling of cold-preconditioning can be measured, mimicked, and modulated to dissect the critical node aspects. Cytokine signaling system analyses require the use of sensitive and reproducible multiplexed techniques. We use quantitative PCR for TNF-&alpha; to screen for microglial activation followed by quantitative real-time qPCR array screening to assess tissue-wide cytokine changes. The latter is a most sensitive and reproducible means to measure multiple cytokine system signaling changes simultaneously. Significant changes are confirmed with targeted qPCR and then protein detection. We probe for tissue-based cytokine protein changes using multiplexed microsphere flow cytometric assays using Luminex technology. Cell-specific cytokine production is determined with double-label immunohistochemistry. Taken together, this brain tissue preparation and style of use, coupled to the suggested investigative strategies, may be an optimal approach for identifying potential targets for the development of novel therapeutics that could mimic the advantages of cold-preconditioning.

We seek to define the neural immune signaling responsible for cold-preconditioning as means to identify novel targets for therapeutics development to protect brain before injury onset. We present strategies for such work that require biological systems, experimental manipulations plus technical capacities that are highly reproducible and sensitive.

Neurological injury is a frequent cause of morbidity and mortality from general anesthesia and related surgical procedures that could be alleviated by ...

Neuroscience

Bilateral Common Carotid Artery Occlusion as an Adequate Preconditioning Stimulus to Induce Early Ischemic Tolerance to Focal Cerebral Ischemia

There is accumulating evidence, that ischemic preconditioning - a non-damaging ischemic challenge to the brain - confers a transient protection to a subsequent damaging ischemic insult. We have established bilateral common carotid artery occlusion as a preconditioning stimulus to induce early ischemic tolerance to transient focal cerebral ischemia in C57Bl6/J mice. In this video, we will demonstrate the methodology used for this study.

There is accumulating evidence, that ischemic preconditioning (PC) &#x2013; a non-damaging ischemic challenge to the brain - confers a transient protection to a subsequent damaging ischemic insult. We established bilateral common carotid artery occlusion (BCCAO) as a preconditioning stimulus to induce early ischemic tolerance (IT) to transient focal cerebral ischemia (induced by middle cerebral artery occlusion, MCAO) in C57Bl6/J mice.

There is accumulating evidence, that ischemic preconditioning - a non-damaging ischemic challenge to the brain - confers a transient protection to a ...

Murine Model of Hindlimb Ischemia 

In the United States, peripheral arterial disease (PAD) affects about 10 million individuals, and is also prevalent worldwide. Medical therapies for symptomatic relief are limited. Surgical or endovascular interventions are useful for some individuals, but long-term results are often disappointing. As a result, there is a need for developing new therapies to treat PAD. The murine hindlimb ischemia preparation is a model of PAD, and is useful for testing new therapies. When compared to other models of tissue ischemia such as coronary or cerebral artery ligation, femoral artery ligation provides for a simpler model of ischemic tissue. Other advantages of this model are the ease of access to the femoral artery and low mortality rate. 
In this video, we demonstrate the methodology for the murine model of unilateral hindimb ischemia. The specific materials and procedures for creating and evaluating the model will be described, including the assessment of limb perfusion by laser Doppler imaging. This protocol can also be utilized for the transplantation and non-invasive tracking of cells, which is demonstrated by Huang et al.1.

Murine Model of Hindlimb Ischemia

The surgical procedure for induction of unilateral hindlimb ischemia is demonstrated, with confirmation of ischemia by laser Doppler perfusion imaging.

In the United States, peripheral arterial disease (PAD) affects about 10 million individuals, and is also prevalent worldwide.  Medical therapies for ...

Biology

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

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

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

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

Using the Electroretinogram to Assess Function in the Rodent Retina and the Protective Effects of Remote Limb Ischemic Preconditioning

The ERG is the sum of all retinal activity. The ERG is usually recorded from the cornea, which acts as an antenna that collects and sums signals from the retina. The ERG is a sensitive measure of changes in retinal function that are pan-retinal, but is less effective for detecting damage confined to a small area of retina. In the present work we describe how to record the &#8216;flash&#8217; ERG, which is the potential generated when the retina is exposed to a brief light flash. We describe methods of anaesthesia, mydriasis and corneal management during recording; how to keep the retina dark adapted; electrode materials and placement; the range and calibration of stimulus energy; recording parameters and the extraction of data. We also describe a method of inducing ischemia in one limb, and how to use the ERG to assess the effects of this remote-from-the-retina ischemia on retinal function after light damage. A two-flash protocol is described which allows isolation of the cone-driven component of the dark-adapted ERG, and thereby the separation of the rod and cone components. Because it can be recorded with techniques that are minimally invasive, the ERG has been widely used in studies of the physiology, pharmacology and toxicology of the retina. We describe one example of this usefulness, in which the ERG is used to assess the function of the light-damaged retina, with and without a neuroprotective intervention; preconditioning by remote ischemia.

The electroretinogram (ERG) is an electrical potential generated by the retina in response to light. This paper describes how to use the ERG to assess retinal function, in dark-adapted rats, and how it can be can be used to assess a neuroprotective intervention, in the present case remote ischemic preconditioning.

The ERG is the sum of all retinal activity. The ERG is usually recorded from the cornea, which acts as an antenna that collects and sums signals from the ...

Quantification of Neurovascular Protection Following Repetitive Hypoxic Preconditioning and Transient Middle Cerebral Artery Occlusion in Mice

Experimental animal models of stroke are invaluable tools for understanding stroke pathology and developing more effective treatment strategies. A 2 week protocol for repetitive hypoxic preconditioning (RHP) induces long-term protection against central nervous system (CNS) injury in a mouse model of focal ischemic stroke. RHP consists of 9 stochastic exposures to hypoxia that vary in both duration (2 or 4 hr) and intensity (8% and 11% O2). RHP reduces infarct volumes, blood-brain barrier (BBB) disruption, and the post-stroke inflammatory response for weeks following the last exposure to hypoxia, suggesting a long-term induction of an endogenous CNS-protective phenotype. The methodology for the dual quantification of infarct volume and BBB disruption is effective in assessing neurovascular protection in mice with RHP or other putative neuroprotectants. Adult male Swiss Webster mice were preconditioned by RHP or duration-equivalent exposures to 21% O2 (i.e. room air). A 60 min transient middle cerebral artery occlusion (tMCAo) was induced 2 weeks following the last hypoxic exposure. Both the occlusion and reperfusion were confirmed by transcranial laser Doppler flowmetry. Twenty-two hr after reperfusion, Evans Blue (EB) was intravenously administered through a tail vein injection. 2 hr later, animals were sacrificed by isoflurane overdose and brain sections were stained with 2,3,5- triphenyltetrazolium chloride (TTC). Infarcts volumes were then quantified. Next, EB was extracted from the tissue over 48 hr to determine BBB disruption after tMCAo. In summary, RHP is a simple protocol that can be replicated, with minimal cost, to induce long-term endogenous neurovascular protection from stroke injury in mice, with the translational potential for other CNS-based and systemic pro-inflammatory disease states.

This protocol describes repetitive hypoxic preconditioning, or brief exposures to systemic hypoxia that reduce infarct volumes and blood-brain barrier disruption following transient middle cerebral artery occlusion in mice. It also details dual quantification of infarct volume and blood-brain barrier disruption after stroke to assess the efficacy of neurovascular protection.

Experimental animal models of stroke are invaluable tools for understanding stroke pathology and developing more effective treatment strategies. A 2 week ...

Induction and Assessment of Ischemia-reperfusion Injury in Langendorff-perfused Rat Hearts

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for myocardial infarction and cardiac complications of thoracic surgery. The ability of certain drugs to precondition the myocardium against ischemia reperfusion injury has led to multiple clinical trials, with little success. The isolated heart model allows acute observation of the functional effects of ischemia reperfusion injury in real time, including the effects of various pharmacological interventions administered at any time-point before or within the ischemia-reperfusion injury window. Since brief periods of ischemia can precondition the heart against ischemic injury, in situ aortic cannulation is performed to allow for functional assessment of non-preconditioned myocardium. A saline filled balloon is placed into the left ventricle to allow for real-time measurement of pressure generation. Ischemic injury is simulated by the cessation of perfusion buffer flow, followed by reperfusion. The duration of both ischemia and reperfusion can be modulated to examine biochemical events at any given time-point. Although the Langendorff isolated heart model does not allow for the consideration of systemic events affecting ischemia and reperfusion, it is an excellent model for the examination of acute functional and biochemical events within the window of ischemia reperfusion injury as well as the effect of pharmacological intervention on cardiac pre- and postconditioning. The goal of this protocol is to demonstrate how to perform in situ aortic cannulation and heart excision followed by ischemia/reperfusion injury in the Langendorff model.

The isolated rat heart is an enduring model for ischemia reperfusion injury. Here, we describe the process of harvesting the beating heart from a rat via in situ aortic cannulation, Langendorff perfusion of the heart, simulated ischemia-reperfusion injury, and infarct staining to confirm the extent of ischemic insult.

The biochemical events surrounding ischemia reperfusion injury in the acute setting are of great importance to furthering novel treatment options for ...

Methods for Acute and Subacute Murine Hindlimb Ischemia

Peripheral artery disease (PAD) is a leading cause of cardiovascular morbidity and mortality in developed countries, and animal models that reliably reproduce the human disease are necessary to develop new therapies for this disease. The mouse hindlimb ischemia model has been widely used for this purpose, but the standard practice of inducing acute limb ischemia by ligation of the femoral artery can result in substantial tissue necrosis, compromising investigators&#39; ability to study the vascular and skeletal muscle tissue responses to ischemia. An alternative approach to femoral artery ligation is the induction of gradual femoral artery occlusion through the use of ameroid constrictors. When placed around the femoral artery in the same or different locations as the sites of femoral artery ligation, these devices occlude the artery over 1 - 3 days, resulting in more gradual, subacute ischemia. This results in less substantial skeletal muscle tissue necrosis, which may more closely mimic the responses seen in human PAD. Because genetic background influences outcomes in both the acute and subacute ischemia models, consideration of the mouse strain being studied is important in choosing the best model. This paper describes the proper procedure and anatomical placement of ligatures or ameroid constrictors on the mouse femoral artery to induce subacute or acute hindlimb ischemia in the mouse.

Surgical induction of hindlimb ischemia in the mouse is useful to examine angiogenesis, however this is compromised in certain inbred mouse strains that display marked ischemia-induced tissue necrosis. Methods are described to induce subacute limb ischemia using ameroid constrictors to circumvent this problem through the induction of gradual arterial occlusion.

Peripheral artery disease (PAD) is a leading cause of cardiovascular morbidity and mortality in developed countries, and animal models that reliably ...

Spinal Cord Neurons Isolation and Culture from Neonatal Mice

We present a protocol for the isolation and culture of spinal cord neurons. The neurons are obtained from neonatal C57BL/6 mice and are isolated on postnatal day 1-3. A mouse litter, usually 4-10 pups born from one breeding pair, is gathered for one experiment, and spinal cords are collected individually from each mouse after euthanasia with isoflurane. The spinal column is dissected out and then the spinal cord is released from the column. The spinal cords are then minced to increase the surface area of delivery for an enzymatic protease that allows for the neurons and other cells to be released from the tissue. Trituration is then used to release the cells into solution. This solution is subsequently fractionated in a density gradient to separate the various cells in solution, allowing for neurons to be isolated. Approximately 1-2.5 x 106 neurons can be isolated from one litter group. The neurons are then seeded onto wells coated with adhesive factors that allow for proper growth and maturation. The neurons take approximately 7 days to reach maturity in the growth and culture medium and can be used thereafter for treatment and analysis.

This study presents a technique for the isolation of neurons from WT neonatal mice. It requires the careful dissection of the spinal cord from the neonatal mouse, followed by the separation of neurons from the spinal cord tissue through mechanical and enzymatic cleavage.

We present a protocol for the isolation and culture of spinal cord neurons. The neurons are obtained from neonatal C57BL/6 mice and are isolated on ...

Experimental Models to Study the Neuroprotection of Acidic Postconditioning Against Cerebral Ischemia

Stroke is one of the leading causes of mortality and disability worldwide, with limited therapeutic approaches. As an endogenous strategy for neuroprotection, postconditioning treatments have proven to be promising therapies against cerebral ischemia. However, complicated procedures and potential safety issues limit their clinical application. To overcome these disadvantages, we have developed acidic postconditioning (APC) as a therapy for experimental focal cerebral ischemia. APC refers to the mild acidosis treatment by inhaling CO2 during reperfusion following ischemia. Here we present two models to execute APC in vitro and in vivo, respectively. The oxygen-glucose deprivation (OGD) treatment of mice and the corticostriatal occlusion and middle cerebral artery occlusion (MCAO) of mice were employed to mimic cerebral ischemia. APC can be simply achieved by transferring brain slices to acidic buffer bubbled with 20% CO2, or by mice inhaling 20% CO2. APC showed significant protective effects against cerebral ischemia, as reflected by tissue viability and brain infarct volume.

Acidic postconditioning protects against cerebral ischemia. Here we present two models to execute APC. They are achieved respectively by transferring corticostriatal slices to acidic buffer after oxygen-glucose deprivation in vitro and by inhaling 20% CO2 after middle cerebral artery occlusion in vivo.

Remote Limb Ischemic Preconditioning: A Neuroprotective Technique in Rodents

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Experimental Models to Study the Neuroprotection of Acidic Postconditioning Against Cerebral Ischemia