To compare the severity of experimental procedures and behavioural tests from an animal’s perspective, novel methods are required. Theoretically, one feasible approach could be the use of a conditioned place preference test (CPP). This test employs the preference for a certain area in a test apparatus being associated with an experimental treatment. Traditionally, the CPP is used to investigate, for example, the effects of drugs. Instead, we aimed to develop a protocol that would enable us to compare the effects of different experimental procedures conducted with mice. Nine experiments with C57BL/6J mice were performed, varying the setup, the procedure duration, the stimuli as well as the presentation order. None of the tested protocols resulted in a distinct preference. Moreover, even simple protocols using food reward as a treatment failed to result in a conditioned place preference. In summary, none of the protocols was sufficient to form a reliable association between conditioned and unconditioned stimulus. We have scrutinized the experimental setup in detail, and we cannot present a solution yet. However, hopefully, our findings will help to create a working CPP to compare the severity of different experimental procedures for mice.
