Reducing animal numbers in tasks of memory

Spontaneous recognition tasks are used extensively in studies of Alzheimer’s disease and other conditions (including normal ageing) where memory loss and decline in cognitive function are consequences of the condition. In these spontaneous recognition tests, the animals simply explore the environments (and objects) around them. Their preference for novelty means that any difference in exploration of different objects can be used as a measure for the animals’ memory of previously seen objects. These tests of object memory (or more complex memory of objects and places or objects and contexts) primarily use one trial per animal (or when multiple trials are used they are carried out at one trial per day). This results in slow data collection as well as large levels of variability in test animal behaviour which requires large numbers of animals to produce sufficient statistical power.

Through an NC3Rs-funded PhD studentship, the team at Durham University led by Dr Alex Easton, have developed an apparatus that allows multiple trials by a single rat to be run in a single session with no handling between trials. This produces a significant reduction in animal numbers (50%) required on this task. In addition, the lack of handling reduces stress in the animals. This allows these tasks to be more widely used in experimental settings, with both greater throughput of data and more subtle changes in behaviour able to be observed.

To encourage wider adoption of the apparatus, especially within industry, they will collaborate with GlaxoSmithKline (GSK, Shanghai), to develop it from its current format (manually operated and only tested in rats) to an easily used format for all users (i.e. automated and useful for all rodents). In addition, the apparatus will be validated using compounds provided by GSK. This project has been supported through CRACK IT Solutions funding.

Full details about this CRACK IT Solution can be found on the CRACK IT website.

The team has successfully tested mice in an adapted version of the original rat apparatus and demonstrated that it is possible to reduce by approximately 50% the number of animals required. Traditional single trial per day spontaneous recognition memory approaches requires 16 - 20 mice being tested for many days. However, the new apparatus generates highly reliable data on common tasks of memory (spontaneous object recognition and object location) using just eight mice running multiple trials consecutively without handling.

They have also demonstrated using a mouse model of Alzheimer's disease (TASTPM) that the equivocal results generated in standard one trial a day procedures using these mice could be due to anxiety in early trials which diminishes over the course of multiple trials. In our apparatus the TASTPM mice showed no significant impairment in common tasks of memory, contradicting some reports in the literature. This is an important result and suggests that the type of prolonged testing without handling provided by the apparatus the team has developed will provide more reliable data which is less prone to misinterpretation.

The combination of verifying the apparatus works for mice, and demonstrating that the results are more reliable and less susceptible to artefacts (such as anxiety) has completely changed the practice of working in their own laboratory. All behavioural studies they carry out using spontaneous tasks in both rats and mice now use a version of a continual trials apparatus. In addition, collaborations they have with other institutions are now utilising this approach – for example, they are building a new apparatus for mice to ship to Leicester University for work on spontaneous recognition tasks in mouse models of disease there. 

The team is continuing their collaboration with GSK to test in the apparatus other mouse models they commonly use for memory studies. They will also explore ways of maximising the usability of the apparatus for industry, including automation and/or alternative spontaneous tasks such as the episodic memory task.

Furthermore, they are keen to support the wider memory research community by identifying opportunities for the adoption of this new approach. They have developed a survey to better understand the appetite for uptake of the apparatus and what barriers might exist to prevent this. If you would like to know more about the model please contact Dr Alex Easton directly.

Chan M, Eacott MJ, Sanderson DJ, Wang J, Sun M, Easton A (2018). Continual Trials Spontaneous Recognition Tasks in Mice: Reducing Animal Numbers and Improving Our Understanding of the Mechanisms Underlying Memory. Frontiers in Behavioral Neuroscience. 12: 214 doi:10.3389/fnbeh.2018.00214

Chan M, Austen JM, Eacott MJ, Easton A, Sanderson DJ (2019). The NMDA receptor antagonist MK-801 fails to impair long-term recognition memory in mice when the state-dependency of memory is controlled. Neurobiology of Learning and Memory 161: 57- 62. doi: 10.1016/j.nlm.2019.03.006