Behavioral responses to ingestion of different sources of fat. Involvement of serotonin?

In previous experiments, we described a decrease in extracellular hypothalamic serotonin, 5-hydroxy-tryptamine (5-HT), in response to ingestion of a lard meal. This effect was related to the low satiating potency of lard as compared with other nutrients. Since the composition in fatty acids might be important for these effects, the purpose of this study was to analyze the neurochemical and behavioral responses to ingestion of different sources of fat. Unique meals of three margarines used in human feeding were compared with a meal of lard with regard to their effects on hypothalamic 5-HT, satiety, anxiety-like behavior and sucrose consumption. A vegetable margarine with a high content in saturated fatty acids also decreased hypothalamic 5-HT while ingestion of a sunflower oil and an olive oil enriched margarines, both high in polyunsaturated fatty acids, did not affect significantly 5-HT levels. However, these two last ones were not the most satiating. The olive oil margarine induced a tendency to an anxiety-like behavior while lard increased sucrose consumption. Thus, ingestion of fats may alter specifically behavioral responses. The involvement of 5-HT is likely in the case of lard ingestion but probably not for the other sources of fat.