Supported by Merit Review #BX001026 from the Department of Veterans Affairs (LSQ), and use of resources and facilities at VA Puget Sound Health Care System, the Transgenic Resource Core at the University of Washington Nathan Shock Center of Excellence in the Basic Biology of Aging (NIA #5P30AG-013280), and the University of Washington Diabetes Endocrinology Research Center (NIH #P30 DK-17047). We thank Cynthia Pekow DVM and Kari L. Koszdin DVM, VA Puget Sound, provided helpful comments on the manuscript.

The procedure described here was approved by the VA Puget Sound Institutional Animal Care and Use Committee, and complies with the ILAR Guide for the Care and Use of Laboratory Animals.
1. Experimental Preparation
<ol>
	<li>Decide beforehand if blood or tissue collection soon after exercise is necessary, and if so, determine the post-exercise interval for conduction of such procedures. Examples include determination of exercise induced hormone or cytokine release into the circulation (necess...

<ol>
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The authors have no conflicts of interest to disclose.

Described here is a method to assess voluntary running endurance in laboratory mice using a motorized treadmill without the use of a shock grid. This method can reveal differences among sub-lines of C57BL/6 mice that differ in expression of the cytokine IL-15, which in turn causes differences in expression of factors that underlie exercise endurance16,17. In keeping with the principles of the &#8220;Three R&#8217;s&#8221; in laboratory animal science, this method can be used as a more humane alternative, or re...

Obesity, insulin resistance, and type 2 diabetes are interrelated metabolic disorders that exert profound effects on the health of both the U.S. and worldwide populations 1-4. Endurance exercise can prevent, as well as treat, these conditions5,6. Moreover, assessment of gait speed and endurance are utilized clinically as diagnostic tests for frailty, sarcopenia, and the consequences of other disorders such as chronic obstructive pulmonary disease, in human subjects 7.
The biochemical pathways underlying the beneficial effects of endurance exercise on body composition and insulin sensitivity are beginning to be elucidated, using genetically or pharmacologically modified mice that display enhanced or reduced exercise capacity 8-11. However, many such studies have utilized motorized treadmills equipped with shock grids to force mice to run 8-11. Animals who quit running are pushed by the moving treadmill belt onto a grid that delivers an electric foot shock; to escape the negative stimulus, the mice return to running on the belt. Such procedures may introduce psychological stress and avoidance behavior as confounding factors affecting experimental parameters12. Other methods of measuring endurance, such as quantitation of ambulatory activity using a beam-break apparatus or quantitation of in-cage wheel running, may be confounded by modulation of circadian cycles, anxiety, inadvertent training, or food seeking behavior12-16. Moreover, these procedures require single housing, another source of psychological stress for mice. Therefore, a direct measurement of exercise endurance not confounded by stress is needed.
To obviate these concerns, our laboratory has developed and validated a method to assess maximal running capacity and sustained running speed in untrained, na&#239;ve mice using a motorized treadmill not equipped with a shock grid. The space at the end of the running belt, where the shock grid usually resides, then becomes a platform for mice to rest, and provides a place for mice that refuse to run to sit until removed from the apparatus. Mice are encouraged to run by a human observer using gentle tapping or touching with a tongue depressor, coupled with sensitivity to the voluntary willingness to run on the part of the mouse. This method has been used to quantify differences in exercise endurance between genetically-modified and control C57BL/6 mice that differ in expression of the muscle derived cytokine interleukin-15 (IL-15)16,17. This method is a humane refinement that decreases the confounding effects of negative reinforcement caused by use of a shock grid.

<table border="0" cellpadding="0" cellspacing="0" width="667">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Open Rodent Treadmill Exer-3/6</td>
			<td style="width:165px;">Columbus Instruments, Columbus OH</td>
			<td style="width:119px;">1050RM</td>
			<td style="width:167px;">This catalog number is for models without shock grid. Shock grids can be removed manually from older models (Eco 3/6)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Sani Cloth Germicidal Towlettes</td>
			<td style="width:165px;">PDI- Professional Disposables, Inc., Orangeburg, NY</td>
			<td style="width:119px;">n/a; usually ordered through local facility</td>
			<td>Contains 10% isopropyl alcohol; any equivalent product can be used.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Tongue depressors</td>
			<td style="width:165px;">any local supplier</td>
			<td style="width:119px;">n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Laboratory timer</td>
			<td style="width:165px;">any supplier</td>
			<td style="width:119px;">n/a</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">IL-15 TG mice*</td>
			<td style="width:165px;">JAX, Bar Harbor, ME</td>
			<td style="width:119px;">o11002</td>
			<td>Murine IL-15 transgene expressed from modified human alpha-skeletal actin promotor with altered signal sequence to facilitate secretion.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">C57BL/6J mice (wild-type)*</td>
			<td style="width:165px;">JAX, Bar Harbor, ME</td>
			<td style="width:119px;">ooo664</td>
			<td>Control mice for IL-15 TG</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">IL-15 KO mice*</td>
			<td style="width:165px;">Taconic Farms, Germantown, NY</td>
			<td style="width:119px;">4269-M</td>
			<td>Homozygous IL-15 &#34;knockout&#34; mice on C57BL/6 background</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">C57BL/6NTac (wild-type)*</td>
			<td style="width:165px;">Taconic Farms, Germantown, NY</td>
			<td style="width:119px;">B6-M</td>
			<td>Control mice for IL-15 KO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;"></td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">*Optional; mouse lines and treatments can be specific to the experimental protocol.</td>
			<td style="width:165px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

assessment of murine exercise endurance without the use of a shock grid: an alternative to forced exercise

Using laboratory mouse models, the molecular pathways responsible for the metabolic benefits of endurance exercise are beginning to be defined. The most common method for assessing exercise endurance in mice utilizes forced running on a motorized treadmill equipped with a shock grid. Animals who quit running are pushed by the moving treadmill belt onto a grid that delivers an electric foot shock; to escape the negative stimulus, the mice return to running on the belt. However, avoidance behavior and psychological stress due to use of a shock apparatus can interfere with quantitation of running endurance, as well as confound measurements of postexercise serum hormone and cytokine levels. Here, we demonstrate and validate a refined method to measure running endurance in na&#239;ve C57BL/6 laboratory mice on a motorized treadmill without utilizing a shock grid. When mice are preacclimated to the treadmill, they run voluntarily with gait speeds specific to each mouse. Use of the shock grid is replaced by gentle encouragement by a human operator using a tongue depressor, coupled with sensitivity to the voluntary willingness to run on the part of the mouse. Clear endpoints for quantifying running time-to-exhaustion for each mouse are defined and reflected in behavioral signs of exhaustion such as splayed posture and labored breathing. This method is a humane refinement which also decreases the confounding effects of stress on experimental parameters.

This procedure for measuring exercise endurance accurately reflects the molecular and metabolic profile of different strains of C57BL/6 mice that differ in expression of the cytokine IL-15 16,17. Transgenic mice that overexpress IL-15 (IL-15 TG mice) exhibit significantly increased run-to-exhaustion times compared to littermate controls, while mice that lack IL-15 (IL-15 KO mice) exhibit significantly reduced run times prior to reaching exhaustion (Figure 1A). Published studies have shown that...

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Assessment of Murine Exercise Endurance Without the Use of a Shock Grid: An Alternative to Forced Exercise

A method to assess exercise endurance in laboratory mice without the use of a shock grid is demonstrated. This method is a humane refinement that can decrease the confounding effects of stress on experimental parameters.

Using laboratory mouse models, the molecular pathways responsible for the metabolic benefits of endurance exercise are beginning to be defined. The most ...

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18.8K vues.  VA Puget Sound Health Care System. A method to assess exercise endurance in laboratory mice without the use of a shock grid is demonstrated. This method is a humane refinement that can decrease the confounding effects of stress on experimental parameters.