TPH2 and migraine disorder: Tryptophan hydroxylase-2 is the rate-limiting enzyme of central 5-HT synthesis,100 and its gene polymorphisms have been linked to migraine.51,67 Chronic central UCN1 microinjection elevated the Tph2 mRNA expression in the caudal and dorsal subdivision of the DRN, whereas an opposite effect was observed in the ventrolateral part.22 This finding is in contrast with our results as we saw a rise in UCN1 levels but decreased the TPH2 protein content upon CGRP treatment.