Tail handling reduces the value of reward in laboratory mice
Researchers at Newcastle University have found that picking up laboratory mice by the tail makes them less responsive to reward, suggesting a more depressive-like state compared to mice handled using a tunnel.
Mice are the most widely used model species for drug discovery and scientific research. Consequently, it is important to refine laboratory procedures and practices to ensure high standards of welfare and scientific data quality. Recent studies have identified that the standard practice of handling laboratory mice by their tails increases behaviours indicative of anxiety. This can be overcome by handling mice using a tunnel, yet tunnel handling has yet to be widely implemented.
In this study, PhD student Jasmine Clarkson under the supervision of Professor Candy Rowe and colleagues provide the first evidence that tail handling also reduces the amount that mice respond to reward. Anhedonia is a core symptom of clinical depression, and is measured in rodents by assessing how they consume a sucrose solution: depressed mice consume less sucrose and the size of their licking bouts when drinking (their ‘lick cluster sizes’) also tend to be smaller. They found that tail handled mice showed more anhedonic responses in both measures compared to tunnel handled mice, indicative of a decreased responsiveness to reward and potentially a more depressive-like state. Their findings have significant implications for the welfare of laboratory mice as well as the design and interpretation of scientific studies, particularly those investigating or involving reward.
Clarkson, J. M., Dwyer, D.M., Flecknell, P.A, Leach, M.C. and Rowe, C. (2018). "Handling method alters the hedonic value of reward in laboratory mice." Scientific Reports 8(1): 2448.
The NC3Rs offer guidance and training resources on the routine handling of mice, click for further information.