Sprague-Dawley (S-D) and Osborne-Mendel (O-M) rats were fed either a low-fat diet (5 percent corn oil) or high-fat diet (20 percent corn oil) for a six-week-period. Brainstem and duodenal levels of tryptophan, serotonin (5-hydroxytryptamine, 5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) were not