Cat-and-mouse game driven by smell of fear

A mouse has befriended its mortal enemy, the cat, after scientists used genetic methods to tinker with its response to the smell of fear.

The result is the stuff of nightmares for fans of Tom and Jerry: a rodent that, unlike its peers, shows no sign of anxiety or panic when presented with the smell of a cat, or even the real thing.

Using sophisticated genetic engineering, they tinkered with a brain circuit in research that both demonstrates the power of a new technique to show what brain circuit do and suggests mice, and humans, are born with a fear of certain smells.

The innate tendency of mice to shy away from the smell of danger can be switched off by simply turning off certain nerve cells that detect smells in the nose, even though the same mice can still be taught to avoid the odour of felines, says the study published today in Nature.

The resulting "delta-D" mutant mice were also able to discriminate other smells but "was not afraid of cat odours, and approached the cats without a...