Modulation of serotonin [5-hydroxytryptamine (5-HT)] signaling by blocking uptake or increasing release from neurons by acting as substrates for 5-HT transporter (sertraline) proteins (Fuller et al., 1988; Gobbi and Mennini, 1999; Baumann et al., 2000; Rothman et al., 2010) may be the mechanism of action for fenfluramine in patients with DS, though a detailed analysis of precisely how fenfluramine modulates excitability via this signaling pathway has not been performed. Here, SLC6A4 is linked to Dravet syndrome.