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Why a Whiff of Cats or Rats Is Scary

Why a Whiff of Cats or Rats Is Scary

Scientists from The Scripps Research Institute have found a specific chemical compound secreted by many predators that makes mice behave fearfully.

The research helps scientists better understand animal behavior, 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 behaviors," said Scripps Research Associate Professor Lisa Stowers. "Our latest research helps shed light on how this brain circuits work."

Mice - even those that have never before encountered other species - will act fearfully when exposed to the odor of many different kinds of predators, including cats, rats, snakes, ferrets, weasels, and foxes . This is the first time that scientists have been able to identify the distinct chemical signal evoking this response and understand how mice are able to detect this signal.

The Smell of Fear

Identifying the chemical pathway of signals that make their way through the neurological system is not easy. One of the challenges for scientists studying brain circuits is that the brain is constantly changing through learning and memory. How a brain detects and then responds to the scent of a particular food, for instance, evolves as the animal learns about that food.

But certain behaviors tend to be the same each time they are triggered, suggesting a steady pathway through neurological circuits. The Stowers group has focused its research program on understanding a number of these steady pathways involving smell - specifically, chemical cues that are released into the air, secreted from glands, or excreted in urine and picked up by members of the same and different species.

Two years ago, the group published research identifying the pheromone that provokes male-male aggression in mice. The scientists hope eventually to compare and contrast different chemical signals to uncover the general principals of brain response.

In the current study, Stowers and her colleagues investigated the fearful response that mice were known to have to odors emitted by predators.

"It's really interesting behavior," said Stowers. "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."

Cat and MOuse

"If you were a mouse, a mere whiff of a cat, rat or snake would be enough to send you into a fearful state. Now, researchers have discovered what it is that upsets the mice so. (Credit: iStockphoto/Eric Isselée)"

Source: Scripps Research Institute

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