ALTERED CIRCADIAN RHYTHMICITY IN THE WOCKO MOUSE, A HYPERACTIVE TRANSGENIC MUTANT

INDUCED changes in the level of daily activity can alter the period of the mammalian circadian clock. In this report, we examined the period of the circadian rhythm of wheel-running activity in a transgenic neu rological mouse mutant, Wocko. Wocko mice display a dominant behaviora l phenotype that consists of hyperactivity, circling and head tossing. The period of the circadian rhythm of wheel-running activity in const ant dark conditions was significantly shorter in mice expressing the W ocko mutation than in their normal littermates. Total activity, monito red by the interruption of an array of infrared beams, was significant ly elevated in Wocko mice. These findings support the view that sponta neous exercise can modulate the circadian timekeeping system.