SHAH ALAM: You probably know about the cat-chasing-mouse stereotype. However, science has proven that the stereotype is somewhat true as rats do have fear of the smell secreted by cats. Researchers have discovered that there is a specific brain expression that occurred in a rat brain, that display predator-induced defensive behavior despite never having previously experienced a cat.
This brain expression is called c-Fos expression. Using fear conditioning method, which is the learning of a neutral stimulus, a stimulus which initially produces no specific response other than focusing attention; it predicts the appearance of an aversive event and enable the researchers to detect defensive behavior and the increased of c-Fos expression. In this case, Wistar rats were exposed to a piece of fabric collar which had been worn by a domestic cat.
The defensive behavior of the rat were quantified after twenty minutes of the rats being exposed to the cat odour, in a custom-built apparatus containing a small wooden `hide box' in a larger arena. After one hour following this session, the rats were anesthetized and de-brained using immunohistochemistry (IHC) techniques in order to quantify the amount of c-Fos expression. IHC is the most common application of immunostaining, which is any use of an antibody-based method to detect a specific protein in a sample. This technique involves the process of selectively identifying antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Antigens are toxin or other foreign substance which induces an immune response in the body. Afterwards, the results were compared between cat odor-exposed rats, control odor-exposed rats and an additional group that had remained in their home cages.
It was predicted that rats given a single exposure to cat odor would show high levels of hiding as well as significant c-Fos expression in key brain regions associated with defensive behavior such as the amygdala, hypothalamus and Periaqueductal Gray (PAG). The results were as per predicted, whereby rats exposed to cat odour spent more than 87% of their time in the hide box during a single twenty minutes exposure session, whereas rats exposed to a control odour (an unworn collar) spent less than 20% of their time hiding. Along with, cat odor-exposed rats showed greater c-Fos expression than controls in many brain regions associated with defensive behavior stated above.
This has shown how the people who have long associated cats as the natural enemy of rats are somehow correct. As a single exposure to cat odor induces a powerful defensive response in rats, causing the rats to spent less time in the open and more time moving to shelter.
Journal reference: 10.1016/S0306-4522(01)00150-6
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