Differences Between d-Fenfluramine and d-Norfenfluramine in Serotonin Presynaptic Mechanisms

Abstract: The abilities of d -fenfluramine ( d -F) and that of d -norfenfluramine ( d -NF) to inhibit [³H]serotonin ([³H]5-HT) accumulation in normal and reserpinized synaptosomes were compared to establish to what extent the serotonin-releasing activity of the two drugs might contribute to reduced accumulation of [₃H]5-HT. The results indicate that the inhibitory action of ( d -NF) on [³H]5-HT accumulation is due principally to its ability to release [³H]5-HT. In contrast, the interference of release in accumulation studies does not seem to play an important role for d -F, suggesting that release from the granular pool and true uptake inhibition are two different mechanisms by which d -F affects serotonin neurons in vitro .