Melatonin inhibits cortical spreading depression-evoked trigeminal nociception.

This study was conducted to determine the effect of melatonin on cortical spreading depression-evoked trigeminovascular nociception. Melatonin (20 or 40 mg/kg) or saline was given to Wistar rats. KCl was placed on the cortical surface to elicit the cortical spreading depression. Cortical blood flow was monitored and ultrastructure of cerebral microvessels was studied. The medulla and cervical cord were removed for Fos and nitric oxide synthase immunohistochemical study. The results showed that melatonin pretreatment significantly minimized the cortical spreading depression-evoked cerebral hyperaemia and attenuated the cortical spreading depression-induced microvascular changes. Pretreatment with melatonin also reduced the number of Fos and nitric oxide synthase immunoreactive cells in the trigeminal nucleus caudalis. The results of this study suggest that melatonin can attenuate the process of trigeminovascular nociception induced by cortical spreading depression.