Enhanced novelty-induced activity, reduced anxiety, delayed resynchronization to daylight reversal and weaker muscle strength in tenascin-C-deficient mice.

Tenascin-C (TNC) is an extracellular matrix protein with multiple and important functions during development and in the adult. We here present a study on the behaviour of TNC-deficient (knockout, KO) mice. Longitudinal experiments including tests for circadian activity, exploration, state and trait anxiety, motor coordination and cognition were performed. KO mice showed increased reactivity to explore a novel environment and decreased anxiety. Spontaneous circadian activity was unaffected, but KO mice showed delayed resynchronization to daylight reversal. TNC deficiency caused weaker muscle strength, whereas gait, coordination and motor learning were unaltered. Short- and long-term memory in the fear conditioning task and working memory in the spontaneous alternation test were normal in KO mice. KO mice showed impaired memory recall in the step-down, but not in the step-through, passive avoidance task. Ethological observation of mice behaviour and principal component analyses indicated that the higher novelty- and stress-induced active responses of KO mice account for their poorer performance in passive avoidance tasks, whereas cognitive abilities are unaltered. The present study extends and corrects previous results, and is an example of how an ethological approach allows a precise description and interpretation of the behavioural alterations of mutant mice.