The crucial factor for the locomotion of rats is the activity of forelimbs. Impairment of the control of a single forelimb brings alteration of motor activity of a degree that could be identified in the open field test. Three groups of adult Wistar rats were used: A Control group A (healthy animals), Marcain group B (blockade of the nerves of the right forelimb plexus by Marcain), Sham group C (Aqua for injection was used instead of Marcain). For the horizontal locomotion the average time spent in locomotion (s), average distance travelled (m) and average speed of locomotion (m/s) during one hour, at time intervals of ten minutes were recorded. Results confirm the role of forelimbs for locomotion of rats - inactivation of one forelimb brings reduction of all parameters of locomotion (p