Dextrofenfluramine, but not 8-OH-DPAT affects the decrease in food consumed by rats submitted to physical exercise.

Abstract

The effects of physical exercise (1 hr of treadmill running) on nocturnal food consumption were investigated in trained rats. On the basis of previous reports which indicated that exercise increases central 5-HT synthesis, we also measured the consequences of 5-HT (indirect or direct) agonist administration. Noncumulative food intake data revealed that exercise diminished food consumption during the late postexercise periods whereas that of the first 4 hr of analysis remained unaltered. Treatment with dextrofenfluramine (d-FEN) at the end of the exercise session promoted hypophagia in both groups of rats; however, the anorexigenic effect of the 5-HT releaser and 5-HT uptake inhibitor d-FEN was found to be more pronounced in the runners. Lastly, an attempt was made to modify the feeding consequences of exercise by administering at the end of running an orexigenic compound, namely the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). At the two doses used, 8-OH-DPAT proved to be inactive on the respective amounts of food consumed by the controls and the runners. The data obtained herein suggest that (a) moderate exercise promotes late hypophagia, (b) 8-OH-DPAT is devoid of hyperphagic property when administered at the onset of the dark cycle, i.e., when the rats normally begin their gross daily food intake. The data obtained from the d-FEN study suggest that exercise-induced alterations in central serotonergic system could participate in the consequences of exercise on feeding behavior.