A Mouse Model of Fatigue Induced by Peripheral Irradiation

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.