EN
Carbon dioxide (CO2) is commonly used for euthanasia in mice but this method has been strongly criticised concerning animal welfare. Alternatives have not been sufficiently tested. Here, we investigate distress induced by exposure to CO2, isoflurane (Iso), and sevoflurane (Sevo). NMRI mice were exposed to 100% CO2 with different filling rates (20% (CO2 20), 60% (CO2 60), CO2 100% (CO2 100) of chamber volume/min) or Iso and Sevo in different concentrations (Iso 2%, Iso 5%, Sevo 4.8%, Sevo 8%). Control animals received airflow. We measured changes in behaviour, and vocalisations during induction until surgical tolerance (ST) or during 5 min of air exposure. Then, mice were decapitated and blood glucose, plasma adrenaline (A) and noradrenaline (NA) were measured. ST was reached fastest after exposure to CO2 100, followed by CO2 60,