Pinch-induced catalepsy in mice.

Pinch-induced catalepsy was readily obtained in five strains of mice following repeated administration of strong pinches at the scruff of the neck. This catalepsy outlasted the pinch by minutes and was more easily induced on retests 48 hr after the initial acquisition tests. Repetitive tail pinches and/or exposure to the testing procedure without pinches also resulted in immobility; however, this was weak in magnitude and short in duration. Treatments designed to prevent immobility between trials (swimming in water or housing in the home cage with normally behaving littermates) failed to block or modify pinch-induced catalepsy. Spacing the trials up to one pinch per 10 min did not affect the emergence of pinch-induced catalepsy, but at one pinch per 30 min it was abolished. Pinch-induced catalepsy is strikingly similar to the behavior elicited in mice when attacked by a cat. In both cases, immobility is produced by pinches or bites at the scruff of the neck, and it outlasts the duration of the stimulus. These results support the notion of pinch-induced catalepsy as an adaptive coping strategy, increasing the chance of survival in predator/prey confrontations.