Bacterial endotoxin and infection cause behavioural hypothermia in infant mice

1. When placed in a temperature gradient, 3-10 day old mice injected with living Escherichia coli or with E. coli endotoxin, select 2-3 degrees C lower temperatures than their litter-mate controls injected with saline. 2. At the lower selected temperature (32 degrees C) young mouse pups resist bacterial infection for longer and tolerate higher doses of endotoxin than at the temperature selected by the controls (35 degrees C). 3. It is possible that a controlled hypothermic state, here called cryexia, is in small mammals an alternative strategy to fever for coping with infections.