The authors would like to thank Michele Allen of the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) for generously sharing her expertise in murine phenotyping methods and for her ongoing technical assistance, as well as for Timothy Hunt of NHLBI for helping us develop the shielding device. This study is supported by the Division of Intramural Research of the National Institute of Nursing Research of the NIH, and part of the validation trial is supported by a grant from the Oncology Nursing Society Foundation.

Ethics Statement: This study was approved by the National Institutes of Health (NIH) Animal Care and Use Committee. All investigators taking part in animal handling and measurement of study outcomes were properly trained by the NIH Office of Animal Care and Use and the National Heart, Lung, and Blood Institute Murine Phenotyping Core. All aspects of animal testing, housing, and environmental conditions used in this study were in compliance with The Guide for the Care and Use of Laboratory Animals11</sup...

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We have described a protocol using targeted peripheral irradiation to induce a reduction of VWRA in mice without confounding morbidity or mortality. Importantly, a simple shielding device allows irradiation in this protocol to target a desired region consistently, mimicking the radiation treatments received by patients with pelvic cancer. In contrast to existing CRF models involving brain or total body irradiation8,9, this model explores how a peripherally-target...

Cancer-related fatigue (CRF) is a distressing and costly condition that often affects patients receiving cancer treatments1. The fatigue is neither proportional to recent activity nor alleviated by rest, and it is associated with a wide variety of disturbances related to mood, motivation, attention, and cognition2. The biological causes of CRF are unknown, though it has been shown in many cases to correlate with inflammation and cytokine levels, also in some cases with hemoglobin levels and the function of various hormone systems (see Saligan et al.3 for a review of biological studies of CRF).
Controlled studies using animal models are necessary to understand the behavior and biology associated with this complex condition. While tumor-related4 or chemotherapy-related5,6 fatigue has been studied in rodent models, the etiology of CRF may be treatment-specific. To investigate CRF related to radiation therapy, our group has recently developed a mouse model of irradiation-induced fatigue7. In contrast to existing CRF models involving brain or total body irradiation8,9, this model explores how a change in centrally-driven behavior, like fatigue, can be triggered by a peripherally-targeted irradiation procedure.
The procedure described here is designed to model radiation therapy administered to patients with pelvic cancer, using lead shielding to target the lower abdominal/pelvic region with irradiation. However, by modifying the lead shielding or its placement relative to experimental animals, this procedure could be adapted to model irradiation of other parts of the body. Voluntary wheel-running activity (VWRA) is used to measure fatigue-like behavior; because it&#39;s a voluntary and normal behavior10, it should allow the concurrent use of other behavioral and biological tests. We have found that peripheral irradiation is sufficient to reduce VWRA in mice without causing overt morbidity7. Future experiments with this model may help reveal effects of peripheral irradiation on immune and other biological signaling, as well as the downstream changes in the central nervous system that can produce deficits associated with CRF.

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			<td style="width:591px;">One-inch thick lead shielding arranged as two boxes with a one-inch thick gap between them for targeted irradiation</td>
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a mouse model of fatigue induced by peripheral irradiation

Cancer-related fatigue (CRF) is a distressing and costly condition that often affects patients receiving cancer treatments, including radiation therapy. Here we describe a method using targeted peripheral irradiation to induce fatigue-like behavior in mice. With appropriate shielding, the irradiation targets the lower abdominal/pelvic region of the mouse, sparing the brain, in an effort to model radiation treatment received by individuals with pelvic cancers. We deliver an irradiation dose that is sufficient to induce fatigue-like behavior in mice, measured by voluntary wheel-running activity (VWRA), without causing obvious morbidity. Since wheel running is a normal, voluntary behavior in mice, its use should have little confounding effect on other behavioral tests or biological measures. Hence, wheel running can be used as a feasible outcome measure in understanding the behavioral and biological correlates of fatigue. CRF is a complex condition with frequent comorbidities, and likely has causes related both to cancer and its various treatments. The methods described in this paper are useful for investigating radiation-induced changes that contribute to the development of CRF and, more generally, to explore the biological networks that can explain the development and persistence of a peripherally-triggered but centrally-driven behavior like fatigue.

Three batches of mice were run through the protocol described above. There were a total of 16 sham and 20 irradiated (2,400 cGy, 3 x 800 cGy/day) mice. After three consecutive days of irradiation, the irradiated group showed significantly reduced VWRA compared to sham (mixed repeated measures ANOVA: main effect of irradiation treatment, F1,13 = 19.233, p &#60; 0.001). The effect was significant for the first seven days after irradiation (simple main effects, p &#60; 0.05 with B...

Watch this Scientific Journal Video about A Mouse Model of Fatigue Induced by Peripheral Irradiation at JoVE.com

A Mouse Model of Fatigue Induced by Peripheral Irradiation

We describe a method using targeted peripheral irradiation to induce fatigue-like behavior in mice. The selected non-lethal irradiation dose leads to a week-long reduction in voluntary wheel-running activity.

Cancer-related fatigue (CRF) is a distressing and costly condition that often affects patients receiving cancer treatments, including radiation therapy. ...

The overall goal of this procedure is to measure fatigue-like behavior induced by peripheral irradiation. This method can help answer key questions about fatigue and, in particular, fatigue related to irradiation. For example, it can be used to explore the different roles of the immune system and the central nervous system in fatigue after irradiation.The main advantage of this technique is that it specifically uses peripheral irradiation to affect essentially driven fatigue behavior. Begin by randomizing the mice into either sham irradiated control or irradiated groups. Then, identify five-week-old, male mice by tail tattoo, and assign each mouse to an individual, standard ventilated mouse cage.Allow mice to acclimate to their cages for at least three more days, handling each mouse gently for a period of three minutes per day. Next, introduce the mice to individual, voluntary wheel-running activity, or VWRA, cages, each equipped with a running wheel connected to an electronic counter for continuous recording. Initiate recording of VWRA through the computer software interface.Set recording intervals to one hour and the duration to at least five days. Finally, after five days, stop VWRA recording through the software interface, and return the mice to their standard cages without running wheels. After anesthetizing the mouse, confirm that the anesthesia was effective with a toe pinch.Use ointment on the eyes to prevent dryness. Next, transfer the anesthetized mouse into a lead shielding device. Arrange the mouse in the shielding so that only the lower abdominal and pelvic region is exposed.Then, use medical tape to secure the base of the mouse's tail in position within the shielding to ensure that the position does not change during irradiation. If the mouse is in the irradiation group, deliver 800 centigray at a dose rate of about 110 centigray per minute. If the mouse is in the sham irradiation control group, leave the mouse in the inactive irradiator for the equivalent time.After irradiation is complete, remove the mouse from the irradiator and shielding and return it to its original standard cage. Monitor the mouse continuously until it has regained sufficient consciousness to maintain sternal recumbency. After three successive days of irradiation, transfer the mice into their individual VWRA cages.Finally, to capture radiation-induced fatigue, record VWRA for 15 days. The effect was significant for the first seven days after radiation, with the lowest mean VWRA distance occurring on the third day after radiation. Here, the distribution of the change in VWRA from before to after irradiation is shown.While the majority of mice tested showed fatigue-like symptoms, there was a small number of mice that showed little change or even an increase in VWRA. While attempting this procedure, it's important to make sure the mice are completely anesthetized during irradiation since any movements may affect the irradiation targeting and dosage. After watching this video, you should have a good understanding of how to use peripherally targeted irradiation to induce fatigue-like behavior in mice.

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7.7K visualizações.  National Institutes of Health. The overall goal of this procedure is to measure fatigue-like behavior induced by peripheral irradiation. This method can help answer key questions about fatigue and, in particular, fatigue related to irradiation. For example, it can be used to explore the different roles of the immune system and the central nervous system in fatigue after irradiation.The main advantage of this technique is that it specifically uses peripheral irradiation to affect essentially driven fatigue behavior. ...