Acute tolerance to amphetamine in rats.

Two groups of rats were given amphetamine intravenously at 5-min intervals (5 or 10 mg/kg/h) for 8 h. Two control groups received saline infusions. On the second day a test dose of 10 mg/kg amphetamine was given to all groups. Body temperature, food intake, and motor behavior were registered every 30 or 60 min. The results showed the development of acute tolerance to the hyperthermic effect within 3-5 h. Tolerance was still visible on the 2nd day. There was also tolerance to the anorectic effect, which was evident on the 2nd day. One element of stereotyped behavior (swaying) also decreased during the amphetamine infusions.