TDK conference 2018

The accuracy of anxiety studies using live animal trials is constantly challenged by the difficulty to create a controllable and yet easily triggered fear response in the test subjects. We proposed the predator odour 2,4,5-trimethylthiazoline (TMT) as a feasible stimulus to elicit anxiety in mice and investigated its effect.

To examine if the fear response was present we used 10% and 100% TMT solutions and several control odours which included citronella as a neutral odour, MHA as an irritating odour, and a perfume as a neutral odour that the mice were acclimated to before the trial. The mice were separately placed in an open field for six minute time intervals with each odour. In the first half of the six minutes, a hiding box was provided. We analyzed the recordings to find fear-related behaviour: moving away from the odour, hiding, freezing and burrowing. Additionally, we looked for a change in levels of movement, body position and grooming behaviour. Our results showed that there was no significant change in behaviour between the trials with TMT and the other odours. The results did not indicate fear behaviour of the mice towards the predator odour.

We theorized that the aversion to the odour is an epigenetically transmitted trait and as epigenetic changes are mostly transmitted over just a few generations, the possibility is discussed, that the mice lost their innate fear response over generations of breeding without a natural environment with predators to induce an epigenetic gene silencing resulting in such behaviour.

Our results showed that it is crucial to test the effect of predator odours on the targeted species or strains before using them as fearful stimuli for anxiety studies.