Time course of the effect of amphetamine on eating is biphasic

The time course of the effect of 1, 2, and 5 mg/kg d-amphetamine sulfate on eating was recorded in independent groups of rats for 12 days with a measure that was sensitive to both increases and decreases in food consumption. The data from the initial drug treatment day suggest that the time course of the drug's effect was biphasic. Furthermore, during the test period, a clear biphasic temporal response developed to the 2- and 5-mg/kg doses. In both cases, on the last drug treatment day, the drug initially suppressed eating but later produced hyperphagia. The hyperphagic response that developed probably resulted from Pavlovian conditioning of compensatory adaptive responses.