The moment in the experiment at which painPain The negative sensory or emotional experience that indicates awareness in the animal of injury or the threat of injury to the body. This negative experience induces changes in an animal’s behavior and physiology, intended to limit the effect of, or avoid the injury, to reduce the chances of repeated injury and to promote recovery. and/or distressDistress It indicates a disadvantageous environment in which the animal is no longer able to adapt in a biologically successful manner to the stressors to which it is exposed. One speaks of distress when the level or the duration of stress are such that significant changes in biological function are required to survive. experienced by the investigational animal is ended or alleviated by either killing the animal humanely or by discontinuing the procedure.