The effect of para-chlorophenylalanine (PCPA) on food consumption, food transit time and melatonin levels in the brain and the digestive tract of mice

1. Food consumption (FC), food transit time (FTT) and melatonin levels in the brain and the digestive tract were determined in control and PCPA-treated mice. 2. FC first increased and then rapidly declined; later returned to its original level. 3. FTT was 22% faster in PCPA treated mice on day 1 but then reached the control levels at day 18. 4. Melatonin levels were higher in PCPA treated mice in the brain, and in all GIT tissues, except the stomach. 5. The described data are consistent with some actions observed after serotonin administration. This paradoxical effect of PCPA is explained by a compensatory feedback mechanism.