Reversal of a feeding-reward system by dexfenfluramine: neurochemical involvement

In addition to its anorectic properties, dexfenfluramine may inhibit some manifestations of feeding-related reward. We attempted to verify this effect by measuring paw-lick latency on the hot plate test in rats conditioned to expect a palatable food. The involvement of variations in beta-endorphinergic, dopaminergic and serotonergic systems was assessed. Despite an inherent effect of increasing paw-lick latency, dexfenfluramine (1.5 mg/kg IP) partly reversed the expectancy-induced increase in this latency. Saline-treated "expectant" rats displayed elevated plasma beta-endorphin levels and reduced hypothalamic 5-HIAA/5-HT and DOPAC/DA ratios. Only the decrease in the DOPAC/DA ratio was reversed by dexfenfluramine, suggesting an involvement of the dopaminergic system in this dexfenfluramine-sensitive reward system.