Predatory stress in mouse

Loss of mouse memory when exposed to rat predatory stress



A number of behavioral conditions such as, fear, anxiety and stress are often correlated with the effect of learning and memory in rodents. The experiments conducted by Yerkes and Dodson (1908), had shown the direct correlation between shock and learning. The mice in shock avoidance task had shown an inverted U-function between learning and foot shock, showing impaired learning with high and low intensity foot shock. The exposure of mice to rats is also a common and stressful experience in the laboratory. Although the mice share same environment in nature, like rats, they usually avoid each other. Some studies also show the effect of predator stress to mice is expressed by the release of the stress hormone corticosterone.

We have tested the hypothesis that predator stress might compromise the learning ability when experienced to the predatory odour. Learning and memory performance of Swiss albino mice was assessed in a Morris water maze (MWM) by exposing them to the odour of predator (Wister rats). Rota rod test was used as a screening measure for muscle coordination followed by a 7 days Morris water maze test including acquisition (1-6 days) and retrieval (day 7) trials to evaluate the effect of rat odour on the spatial memory of Swiss albino mice.

The result revealed that the rat odour stress produced amnesia in the mice but the mice odour could not affect the learning in rats. Moreover the memory loss in mice was comparable to the degree of amnesia produced by scopolamine, a well-known amnesic agent. Therefore, based on the spatial memory analysis, we concluded that the rat odour was a predatory stress and impaired learning in mice.

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