Methamphetamine- and apomorphine-induced changes in spontaneous motor activity using a new system to detect and analyze motor activity in mice

Abstract

A new system was devised to detect animal spontaneous motor activity in more detail, and methamphetamine- and apomorphine-induced changes in spontaneous motor activity were analyzed using this system. The system consists of a doughnut-shaped cage with 36 units of detectors. Scanning of each detector unit was three-dimensionally carried out, and then scanning data were fed into a personal computer. These steps were completed within 0.1 sec and repeated. Spontaneous motor activity was analyzed as changes in parameters, such as total activity, locomotor activity, vertical activity (the number of rearings and the rearing time), motion time, and average speed. Regarding dependence on the dosages of methamphetamine and apomorphine, the time courses of changes in total activity and locomotor activity markedly differed from those for changes in vertical activity. Changes in the numbers of rearings and rearing time induced by 2 mg kg methamphetamine peaked 40–80 min after administration, whereas those in other parameters did so 15–25 min after. Three mg kg apomorphine-induced changes in total activity and locomotor activity showed two peaks 10–15 and 40–50 min after administration, respectively. At the same dosage, apomorphine markedly increased rearing time with slight but not significant effects on the number of rearings. These effects peaked 20–30 min after administration. These results indicate this system to be quite useful to detect and analyze drug-induced changes in spontaneous motor activity.