Characterization of the trigeminovascular actions of several adenosine A(2A) receptor antagonists in an in vivo rat model of migraine

BACKGROUND: Migraine is considered a neurovascular disorder, but its pathophysiological mechanisms are not yet fully understood. Adenosine has been shown to increase in plasma during migraine attacks and to induce vasodilation in several blood vessels; however, it remains unknown whether adenosine can interact with the trigeminovascular system. Moreover, caffeine, a non-selective adenosine receptor antagonist, is included in many over the counter anti-headache/migraine treatments. METHODS: This study used the rat closed cranial window method to investigate in vivo the effects of the adenosine A(2A) receptor antagonists with varying selectivity over A(1) receptors; JNJ-39928122, JNJ-40529749, JNJ-41942914, JNJ-40064440 or JNJ-41501798 (0.3–10 mg/kg) on the vasodilation of the middle meningeal artery produced by either CGS21680 (an adenosine A(2A) receptor agonist) or endogenous CGRP (released by periarterial electrical stimulation). RESULTS: Regarding the dural meningeal vasodilation produced neurogenically or pharmacologically, all JNJ antagonists: (i) did not affect neurogenic vasodilation but (ii) blocked the vasodilation produced by CGS21680, with a blocking potency directly related to their additional affinity for the adenosine A(1) receptor. CONCLUSIONS: These results suggest that vascular adenosine A(2A) (and, to a certain extent, also A(1)) receptors mediate the CGS21680-induced meningeal vasodilation. These receptors do not appear to modulate prejunctionally the sensory release of CGRP. Prevention of meningeal arterial dilation might be predictive for anti-migraine drugs, and since none of these JNJ antagonists modified per se blood pressure, selective A(2A) receptor antagonism may offer a novel approach to antimigraine therapy which remains to be investigated in clinical trials.