Tolerance to amphetamine in cannula vs. bottle-fed animals

The effects of amphetamine on the milk intake, body weight, and behavioral activity of bottle- and cannula-fed rats was investigated in a before/after paradigm. Dose response determinations were conducted before (DR 1) and after (DR 2) chronic treatment (45 days) with amphetamine (8.0 mg/kg) given either before or after milk tests, to determine whether tolerance developed to the anorexic effect of the drug. Control groups were given saline during the chronic phase. Both cannula- and bottle-fed animals lost a significant amount of weight. Cannula-fed animals drank significantly more than bottle-fed animals throughout the chronic phase. Statistical analysis revealed significant increases in intake from DR 1 to DR 2 for the after and saline cannula-fed groups, and the before, after, and saline bottle-fed groups. All groups showed an increase in intake from DR 1 to DR 2, though the increase of the before cannula-fed group failed to reach statistical significance.