Changes in serotonin, serotonin transporter expression and serotonin denervation supersensitivity: involvement in chronic central pain after spinal hemisection in the rat.

Spinal cord injury (SCI) results in abnormal locomotor and pain syndromes in humans. In a rodent SCI model, T13 unilateral spinal hemisection results in bilateral mechanical allodynia and thermal hyperalgesia, partly by interruption of tonic descending serotonin (5-HT) inhibition. In the current study, we examined changes in density and distribution of 5-HT and 5-HT(T) in cervical (C8) and lumbar (L5) enlargements after T13 spinal hemisection and studied the effects of intrathecally delivered 5-HT (10, 21, and 63 microg), 5-HT antagonist methysergide (125 microg/kg), and 5-HT reuptake inhibitor fluvoxamine (75 microg/kg) on pain-related behaviors.

Rapid changes in expression of glutamate transporters after spinal cord injury.

Glutamate is a major excitatory neurotransmitter in the mammalian CNS. After its release, specific transporter proteins rapidly remove extracellular glutamate from the synaptic cleft. The clearance of excess extracellular glutamate prevents accumulation under normal conditions; however, CNS injury elevates extracellular glutamate concentrations to neurotoxic levels.