SLC6A4 and neuropathic pain: In the RVM, increases in serotonin are analgesic with extracellular levels of serotonin controlled by the serotonin transporter (SERT).75,95 The SERT is increased, whereas 5-HT is decreased, in the RVM and brainstem after induction of neuropathic pain.10 Two weeks of treadmill training after induction of neuropathic pain reversed the increases in SERT and decreases in 5-HT with a corresponding reduction in mechanical hyperalgesia10 (Fig. 2C).