How to Improve and Refine the Elevated Plus Maze for Laboratory Mice

The daily light-dark cycles synchronize
behavioural and physiological processes to the external environment.
Light is the most important environmental cue that coordinates many
aspects such as activity, maintenance behaviours, hormonal regulation
or long-term potentiation. Mice are among the main animals used
in behavioural neuroscience and preclinical research laboratories.
Although nocturnal, they are generally tested during day (i.e. during
their resting phase). Even if convenient for the experimenter, a
perturbation of the sleep-wake cycle such as manipulations during day
can generate some stress to the animal, produce few reliable data,
contributing to reproducibility issue,
and may lead to negative consequences for health, physiology,
behaviour and cognition. Then the
testing moment could be an important variable affecting animal
behavior. It appears
that rodents are less anxious during the dark phase, however, a lack
of data regarding the effect the testing moment on behavior has
recently been highlighted. Additionally, several studies
evaluating the effects of the testing moment have shown conflicting
results; these
differences can be explained by various methodological aspects such
as parameters related to the procedure but also by the way of
collecting and interpreting behavioral
data.

In this study, we focused on an anxiety test. We
tested 4 different testing moment to determine if
there is a more appropriate testing moment where
mice show the less anxiety. Previously, we have shown that the way of
analyzing behavior can affect the results. Here, we refined our
observation method to improve the data interpretation.