Chemical signal from cats `sparks fear in mice`

Last Updated: Friday, May 14, 2010 - 13:36

Washington: Ever wondered why that whiff
of cats makes mice scary? Well, it`s the chemical signal from
the predators which sparks fear in rodents, say scientists.

A new study by the Scripps Research Institute has
found the mice are able to detect a specific chemical compound secreted by many predators and it`s this ability which makes them behave fearfully, the `Cell` journal reported.
According to the scientists, the findings may
help better understand animal behaviour, and may eventually
lead to new insights into how sensory information is processed
in human brains.

"We`re interested in how the brain can be hardwired to
respond to chemical signals and how this can lead to complex
behaviours. Our latest research helps shed light on how this
brain circuits work," said lead scientist Prof Lisa Stowers.

In the study, the scientists investigated the
fearful response that mice were known to have to odours
emitted by predators.

"It`s really interesting behaviour. These mice
have been inbred in the lab since the 1930s. For hundreds of
generations, they haven`t been around any other species. It`s
really remarkable that they haven`t lost this circuit," said
co-scientist Lisa Stowers.

To begin, the scientists addressed the issue of how
mice detected these chemical cues from other species.

Mice have two sensory organs -- the vomeronasal organ
(VNO), which is located above the roof of the mouth in nasal
cavity, and the main olfactory epithelium (MOE), found under
the eyeball at the top back portion of the nasal cavity.

Which was responsible for picking up the scent?
To answer this question, the scientists compared the
behaviour of normal (wildtype) mice with mice with a genetic
mutation that left them without functioning vomeronasal
organs.

When the regular mice were put in a cage with a cotton
ball swabbed with rat, cat, or snake odour, the mice reacted
fearfully -- staying away from the cotton ball, repeatedly
striking a cautious posture and exhibiting elevated levels of
stress hormones.

In contrast, the mice without functioning vomeronasal
organs appeared to be curious about the cotton balls and
demonstrated few signs of fear.

From these experiments, the scientists were
able to determine that the vomeronasal organ was essential for detecting chemical cues from predators.

"We did the experiment with quite a few different
animals. One of them actually curled up and slept right next
to the rat. So even though these mice can touch the rat and
see it breathing, without the vomeronasal organ system mice
don`t respond fearfully," Prof Stowers said.

PTI



First Published: Friday, May 14, 2010 - 13:36

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