Serotonin is a type of neurotransmitter, or "communication chemical" which passes messages between nerve cells. It helps to control mood, pain sensation, sexual behaviour and sleep, as well as dilation and constriction of the blood vessels, among other things. Low serotonin levels in the brain may lead to a process of constriction and dilation of the blood vessels which trigger a migraine. Serotonergic agonists, such as triptans, LSD or psilocin, activate serotonin receptors to stop a migraine attack.
Imbalances in brain chemicals, including serotonin — which helps regulate pain in the nervous system — may be the cause of migraines.
Serotonin levels drop during migraine attacks. This may trigger our trigeminal system to release substances called neuropeptides, which travel to the brain's outer covering (meninges). The result is headache pain.