Abstract:
Dihydroergotamine (DHE) is a derivative of ergot alkaloids. Its efficacy is used for vasoconstriction of cranial vessels and can reduce pain in migraine headache. The overuse of DHE is still uncertain. The objective of this study was to investigate the effect of acute and chronic DHE administration in animal induced cortical spreading depression (CSD) and trigeminal nociception. The experiment was divided into 2 groups; the acute-treated group, Wistar rats were received 100 µg/kg DHE, i.v., after the 3rd depolarization waves of CSD was generated and the chronic-treated group, rats were received a once daily 100 µg/kg DHE, i.p., for 0, 7, 14, and 28 days. In the chronic-treated group, the last administration was performed at 30 minutes before CSD induction. The 0.1% dimethyl sulfoxide (DMSO) in 0.9% normal saline was given in the control rats of each group as a vehicle. CSD was induced using application of 3 mg solid potassium chloride and electrocorticogram was recorded within 1 hour and 2 hours for chronic-treated group and acute-treated group, respectively. Trigeminal nociception was studied in brain stem containing trigeminal nucleus caudalis (TNC). The expression of c-Fos protein was examined using western blot analysis. The results showed that acute treatment with DHE significantly decreased the quantity of c-Fos in TNC without the change in CSD patterns. On the contrary, chronic treatment with DHE presented the significant increase in area under the curve (AUC) of CSD waveforms and c-Fos in TNC for 14 and 28 days. These finding indicate that the chronic treatment with DHE can increase the cortical activity and c-Fos expression in trigeminal nociceptive system. This study could support the understanding of DHE-induced medication overuse headache and the pharmacological effect of this drug’s efficacy.
