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 re...

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 border="0" cellpadding="0" cellspacing="0">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<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&#160;</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>Skin temperature recorder</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. ...

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