Pain perception in decapitated rat brain

The question of humaneness of decapitation per se has been considered. The time required for the oxygen tension in decapitated rat brain to decline to a level at which the brain becomes unconscious was estimated to be 2.7 sec. Assuming that decapitation is a powerful arousal stimulus and that the resulting EEG activation (low voltage, fast activity) indicates a conscious awareness of pain and distress the maximum time the pain and distress could be perceived would be 2.7 sec. Hence, decapitation of rats per se may be considered humane.