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Published online 7 November 2007 | Nature | doi:10.1038/news.2007.224
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Fear no smell
Researchers make mice unafraid of the scent of danger.
Just a whiff of the urine from snow leopards sends shivers down the spines of normal mice. But deleting a key group of olfactory cells turns mice fearless in the face of this odour — even though the mice can still smell it, and be taught to fear it later in life.
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Hitoshi Sakano’s findings on rats indicate that smells produce in them innate fear versus the learned fear by dorsal and ventral olfactory cells respectively. The adrenocorticotrophic hormones were produced by normal and not by the altered mice to trimethyl-thiazoline. Any indication whether the same dichotomy exists for the above smell ( or any stress generating smell) between the two types of mice for secretion of catecholamines.
Wouldn't it be interesting to know if cats react differently to these fearless mice than to normal fearful ones?
It is known that in Alzheimer disease there is an early disturbance of smell (like in parkinson disease) probably due to synaptic or neuronal loss in the perirhinal cortex. It would be interesting to know if there is a differentiated loss between these kind of odour perception systems (if they exist also in humans). We often see in the clinic that SDAT patients endanger themselves by not reacting appropriately to some smells that normally should activate "danger" signals: gas, fire, rotten food etc... Dr. G. Otte
Is there not a parasite which performs this same 'trick' on mice naturally, removing the fear response to the smell of cats from the mouse's nervous system, allowing the parasite a better chance to gain entrance to the feline digestive system, which it requires for the next stage of its life cycle? Would be interesting to know if that parasite acts upon the same cells.
It seems like the transgenic mouse does not run away from the cat itself, as shown in the photo. If that is the case, it is an even more impressive result as compared to those obtained with odors of rotting food, fox glands, and the urine of snow leopards.
Mr. Brookfield, I was just thinking that myself--the protozoan parasite in question is Toxoplasma gondii. The last I heard, researchers think it's doing something to the amygdala to mess with fear processing.