Effects of acute methamphetamine administration on spacing in paired rats: investigation with an automated...

1. Effects of acute methamphetamine administration on spacing and locomotor activity were investigated in paired rats using a computer-assisted automated video-analysis method. 2. Both 0.1 and 1 mg/kg of methamphetamine significantly increased the spacing in comparison with saline. This alteration in behavioral interaction by methamphetamine may serve as one of the animal models of social withdrawal. 3. A significant increase in locomotor activity was found after 1 mg/kg of methamphetamine. 0.1 mg/kg dosage was accompanied by a locomotor change of a lesser degree and shorter duration. 4. The difference with respect to the dose dependency and the time course indicates that the changes in these two behavioral indices by methamphetamine may have different underlying mechanisms.