The effect of MK-801 on motor activity and c-Fos protein expression in the brain of adolescent Wistar rats

The changes that occur during adolescence have a profound impact on the brain and behavior later in life. In this work we examined changes in motor activity during habituation to a novel environment and after treatment with MK-801 (0.025, 0.05, 0.1 mg/kg) in peripubertal, pubertal and adult Wistar rats. The involvement of the motor cortex and striatum in motor activity was assessed by analyzing changes in c-Fos protein levels that served as an indicator of neuronal activity. During the habituation period, locomotor activity in peripubertal rats was higher during the first 10 min than in other groups. The same amount of stereotypy-like movements was detected in all three groups. MK-801 induced dose- and age-dependent changes in motor activity. Peripubertal rats were the most sensitive to treatment with MK-801. We also report a surprising finding that systemic application of MK-801 induced a similar age-related profile of changes in motor activity and c-Fos protein expression in the motor cortex but no c-Fos induction in the striatum. Our results demonstrate that, depending on the phase of adolescence the same dose of MK-801 affected behavioral functions in a different manner and that activity of the motor cortex rather than striatal activity was linked to drug-motor activity interactions.