SLC6A4 and migraine disorder: The two most studied components of the serotonergic system that have come into the spotlight in determining susceptibility to migraine as well as multiple neuropsychiatric disorders are the serotonin transporter (SERT, also known as SLC6A4), which reuptakes serotonin from the synapse, and monoamine oxidase A (MAOA), an important enzyme that degrades serotonin and metabolizes triptans [23].