Effects of amphetamine and phenylpropanolamine on latency to feed and cumulative liquid diet intake in rats.

The purpose of the present experiment was to compare the actions of d-amphetamine sulfate (AMP) and phenylpropanolamine hydrochloride (PPA: d,l-norephedrine) on feeding of a liquid diet. Adult rats were deprived of food for 22 hours and treated with 1.0 and 2.0 mg/kg AMP and with 15 and 30 mg/kg PPA 30 minutes prior to a 60-minute feeding test. Latency to begin feeding was recorded at the start of the feeding session with cumulative liquid diet intake recorded every 5 minutes during the test. Amphetamine and PPA significantly increased latency to feed but PPA, at the doses used here, produced a greater reduction in overall feeding during the test sessions than did amphetamine. Eating rate was reduced by both AMP and PPA during the first 20 minutes of the test session, but eating rate after AMP was significantly higher during the latter portion of the test session. Although amphetamine and PPA are often likened as similar in structure and function, these results suggest important qualitative differences between the anorexic activities of these two drugs.