A NEW SYSTEM FOR THE MEASUREMENT AND ANALYSIS OF MOTOR-ACTIVITY IN MICE - EFFECT OF SEVERAL CENTRAL STIMULANTS

To estimate the spontaneous motor activity in mice, a new system with highly stable sensitivity and good reproducibility was made, and the effects of five central stimulants were investigated. The apparatus consists of a doughnut-shaped cage with detectors for measuring spontaneous motor activity; i.e., the number of movements, vertical activity, total distance, etc., for every five min. Methamphetamine (0.5, 1 and 2 mg/kg, s.c.) produced an increase in the number of movement and markedly increased total distance. Cocaine (20, 50 and 75 mg/kg, s.c.) caused a marked increase in movement and total distance. Mice injected with 50 mg/kg of cocaine showed long-lasting locomotion with few stops throughout the observation period. Caffeine (10, 30 and 100 mg/kg, s.c.) produced a long-lasting and moderate excitation. Morphine (5, 10 and 20 mg/kg, s.c.) caused a marked increase in continuous locomotion dose-dependently. Apomorphine produced a transient increase in rearing and locomotion at a dose of 1 mg/kg, s.c.; and it produced long-lasting rearing and moderate locomotor activity at 3 mg/kg. These results suggest that this apparatus is able to detect characteristic changes in spontaneous motor activity produced by central stimulants and may be useful for analyzing drug-induced motor activity in mice in more detail.