Chemical signal from cats 'sparks fear in mice'



Chemical signal from cats `sparks fear in mice` 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