UC Riverside

Defensive behaviors in the presence of predator cues are typical innate behaviors in animals. Although predator signals are best detected with the summation of various sensory modalities in nature, olfactory-specific exposure to a predator specimen is sufficient to yield defensive responses in nocturnal prey animals such as mice. Animals display fixed patterns of defensive behaviors such as freezing, flight, and risk assessment in response to olfactory predator cues. These defensive responses varied between mice of varying age and sex. We found that mice freeze robustly when exposed to freshly collected cat saliva, but with lessened intensity when exposed to saliva that aged several hours. The underlying molecular and neural mechanisms for such shift in behavioral decisions are still not well understood. This freezing behavior was observed only when mice had direct contact with the cat odor and abolished in mice lacking functional Trpc2, indicating that the accessory olfactory system is necessary for this behavioral output. Interestingly, neural activation in some brain areas were with behavioral outputs in the fresh saliva-exposed mice but not in the ones exposed to old saliva. These results suggest that fresh cat saliva contains chemical cues that signal imminence of predator threat, and the signal is processed through a specific population of neurons in the accessory olfactory system. In this study, we reveal the candidate proteins in cat saliva that induces freezing and the mouse sensory receptor that detects them. Our research aims to identify the neural mechanism of imminence of threat detection and shed light on the neural basis underlying the defensive behavioral decision making in prey animals.