title: Effects of ionotropic glutamate receptor antagonists on rat dural artery diameter in an intravital microscopy model.
abstract: OBJECTIVE
  During migraine, trigeminal nerves may release calcitonin gene-related peptide (CGRP), inducing cranial vasodilatation and central nociception; hence, trigeminal inhibition or blockade of craniovascular CGRP receptors may prevent this vasodilatation and abort migraine headache. Several preclinical studies have shown that glutamate receptor antagonists affect the pathophysiology of migraine. This study investigated whether antagonists of NMDA (ketamine and MK801), AMPA (GYKI52466) and kainate (LY466195) glutamate receptors affected dural vasodilatation induced by alpha-CGRP, capsaicin and periarterial electrical stimulation in rats, using intravital microscopy.
  
  
  METHODS
  Male Sprague-Dawley rats were anaesthetized and the overlying bone was thinned to visualize the dural artery. Then, vasodilator responses to exogenous (i.v. alpha-CGRP) and endogenous (released by i.v. capsaicin and periarterial electrical stimulation) CGRP were elicited in the absence or presence of the above antagonists.
  
  
  RESULTS
  alpha-CGRP, capsaicin and periarterial electrical stimulation increased dural artery diameter. Ketamine and MK801 inhibited the vasodilator responses to capsaicin and electrical stimulation, while only ketamine attenuated those to alpha-CGRP. In contrast, GYKI52466 only attenuated the vasodilatation to exogenous alpha-CGRP, while LY466195 did not affect the vasodilator responses to endogenous or exogenous CGRP.
  
  
  CONCLUSIONS
  Although GYKI52466 has not been tested clinically, our data suggest that it would not inhibit migraine via vascular mechanisms. Similarly, the antimigraine efficacy of LY466195 seems unrelated to vascular CGRP-mediated pathways and/or receptors. In contrast, the cranial vascular effects of ketamine and MK801 may represent a therapeutic mechanism, although the same mechanism might contribute, peripherally, to cardiovascular side effects.
authors.affiliation: Department of Internal Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands.
authors.forename: K Y
authors.initials: KY
authors.lastname: Chan
authors.forename: S
authors.initials: S
authors.lastname: Gupta
authors.forename: R
authors.initials: R
authors.lastname: de Vries
authors.forename: A H J
authors.initials: AH
authors.lastname: Danser
authors.forename: C M
authors.initials: CM
authors.lastname: Villalón
authors.forename: E
authors.initials: E
authors.lastname: Muñoz-Islas
authors.forename: A
authors.initials: A
authors.lastname: Maassenvandenbrink
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D008297:Male; D008576:Meningeal Arteries / Q000187:drug effects / Q000378:metabolism; D008853:Microscopy / Q000379:methods*; D008881:Migraine Disorders / Q000188:drug therapy* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D014664:Vasodilation / Q000187:drug effects
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate