Figure 1.

Forearm blood flow response to infusion of acetylcholine or sodium nitroprusside into the brachial artery in patients with migraine during or free from headache, and control subjects. The patients with migraine were studied during the interictal period (group M) or the headache attack (group MH). Data (mean ± SE) were analyzed by analysis of variance for repeated measures. P < 0.05 for the effect of migraine in the acetylcholine (Ach) test and P < 0.05 for the interaction between migraine and Ach. P < 0.005 for the effect of migraine in the nitroprusside test and P < 0.05 for the interaction between migraine and nitroprusside.