Spatiotemporal properties of locomotor activity after administration of central nervous stimulants and sedatives in mice.

In the present study, we investigated the spatiotemporal properties of locomotor activity after administration of CNS sedatives (pentobarbital and diazepam) and stimulants (theophylline and caffeine) in an open field test. The absolute and relative distances traveled in central or peripheral regions within 2 h were analyzed. We found that both pentobarbital and diazepam increased total travel distances, especially within the initial 30 min, when traveling was mainly in the peripheral region. Pentobarbital induced this hyperactivity at higher doses (maximum at 30 mg/kg); while diazepam at higher doses (4 and 8 mg/kg) mainly decreased the traveled distance during 0-1 h but increased that in the periphery during 1-2 h. On the other hand, both theophylline and caffeine generally increased the traveled distance in the central region; this effect lasted longer with increasing dose. Caffeine increased the traveled distance at lower doses (maximum at 10 mg/kg) but decreased it at higher doses (30 and 100 mg/kg) during the initial 1 h. Theophylline exhibited a similar but smaller decrease at higher doses. Thus, we revealed the spatiotemporal properties that sedatives decrease central locomotion but induce a dose-related peripheral hyperactivity while stimulants induce central hyperactivity with a bell-shaped dose-response relation.