The effect of fenfluramine on the microstructure of feeding and drinking in the rat.

1. The effects of three doses of fenfluramine on feeding and drinking in the rat were examined. 2. Feeding and drinking were subdivided into meals and bouts, and the changes in feeding/drinking were expressed in terms of meal/bout frequency, meal/bout size, meal/bout length, and eating/drinking rate. 3. The changes in these parameters were examined over different time periods after the injection. 4. Significant changes in the distribution of inter-response intervals within meals were found in time period 1 with 5 mg/kg and 10 mg/kg doses of fenfluramine. Videotape and computer analysis showed that the changes in inter-response interval histograms differed significantly from those seen in normal animals approaching satiety. Drinking parameters also changed. 5. Compensatory increases in feeding were observed in time period 4 with the 10 mg/kg dose. 6. The difficulties in designing and interpreting experiments in feeding are discussed, and the action of fenfluramine as an anorectic drug is considered.