These agents are effective in preventing migraine, and the response is usually rapid.19 TCAs increase the concentration of serotonin in the synaptic cleft by blocking the transport of serotonin back into the presynaptic neurons.20 Human trigeminal ganglia express abundant 5HT1B/D receptors and serotonin agonists through 5HT1B/D receptors inhibit trigeminal activity in releasing CGRP and consequently affect the release of NO and migraine attacks.21,22. This evidence concerns the gene HTR1B and migraine disorder.