Handling of the Cotton Rat in Studies for the Pre-clinical Evaluation of Oncolytic Viruses

The overall goal of this procedure is to demonstrate the safe handling and capture of cotton rats using a specific method aimed at reducing the stress experienced by the animal. This is accomplished by first placing an enrichment tube against the end of a rat cage and a securable steel basket on top. In the second step, the proper protective personal equipment is dawned and the cotton brat is allowed to crawl into the enrichment tube.

The tube is then held against the side of the cage and the trapped animal is quickly transferred into a plastic container with air holes for transport to the anesthetic induction chamber. In the final step, a special nose cone specifically fitted for the cotton brat snout is placed on the animal to facilitate complete sedation. Ultimately, this capture procedure can be used to safely handle cotton brats in a manner that decreases their stress and increases their safety.

When using these highly excitable rodents in preclinical studies, Generally individuals new to this method will struggle because of the discrepancies in the literature regarding the handling, housing, and demeanor of the cotton rat. Visual Demonstration of this method is critical to compliment the written accounts to prepare researchers for the behavioral challenges in working with cotton rats. Demonstrating the procedure will be Brianne Cuttington, a graduate student, and Megan er, a postdoctoral fellow from my laboratory To decrease in fighting, housed the cotton rats individually in polycarbonate rack cages containing one eighth inch corncob bedding, a section of PVC tubing no longer than eight inches, and nestlets for enrichment to allow for the safe and easy capture of the animals.

Place the enrichment tube against the end of the cage and then sit a securable stale basket over the top of the cage containing rodent food and a water bottle. Now gather a large, clear plastic container with holes for air and a lid and anesthetic induction chamber, large enough to fit the container and a nose cone fitted to the gas output hose. Note that the cotton brat has an elongated snout requiring a different shape to deliver the anesthetic gas as depicted in this image of a nose cone, engineered to properly fit a cotton rat working in pairs.

Researchers should put on thick leather gloves for protection during all parts of the procedure. When both researchers are ready, place the animal's cage on a flat surface and remove the outer lid. Then when the animal is inside the enrichment tube, lift the steel feed tray lightly and slowly maneuver the tube until it is parallel with the sides of the cage and against the back.

Next, slowly and deliberately lift the edge of the steel cover furthest from the enrichment tube, keeping the other end in contact with the cage. Have the second researcher make a space large enough for the plastic container. Then in one smooth, quick motion, push the plastic and container on top of the enrichment tube.

Maintain contact of the container with the side of the cage trapping the animal in the tube. When handling the cotton rats, it is important to be patient and use a steady hand as the animals have a strong flight or fight response, and it'll try to avoid capture by running and jumping out of the cage. If an animal does escape, avoid handling by the tail.

As degloving can occur, Remove the steel feed tray and give the plastic container lid to the other researcher. Then slide the plastic lid between the side of the cage and the container. Being mindful of the trapped animal's appendages in the process and closing, but not sealing the container, making sure the container remains closed.

Transport the animal to the induction chamber. Then have one researcher quickly place the animal in the chamber and remove the container lid in one fluid motion while the other opens and immediately replaces the induction chamber lid. Finally, after administration of the anesthesia, return the rat to its cage with monitoring until the animal regains full mobility and sternal recomp.

The injection of viable tumor cells is important for proper tumor formation. In this image, a healthy monolayer of LCRT cells that can be prepared for injection into cotton brats is shown. In contrast, these LCRT cells have a low viability and should not be used for injections.

The tumors formed from LCRT cells are fast growing, and as a result, necrotic centers often form as such, tumor formation should be monitored carefully to avoid ulceration. If ulceration occurs, the animal should be sacrificed to avoid infection and possible death from sepsis. Maintaining tumor tissue integrity after excision will result in a sample that is a more accurate representation of the tumor in vivo.

For example, here, an excision technique by which the tumor is carefully separated from surrounding tissue using a scalpel and tweezers is shown as shown in this final image. The dense and highly vascularized structure of the tumor is maintained by this excision technique, which is important for the analysis of treatments that affect tumor vasculature. As is the case with many oncolytic viruses While attempting this procedure, it's important to remember to stay calm and to carry out each step slowly and deliberately to avoid agitating the cotton rats.

After watching this video, you should have a good understanding of how to safely capture and handle cotton rats.