HISTAMINE-1 RECEPTOR BLOCKADE DOES NOT PREVENT NITROGLYCERIN INDUCED MIGRAINE - SUPPORT FOR THE NO-HYPOTHESIS OF MIGRAINE

It has previously been shown that in migraine sufferers infusion of gl yceryl trinitrate (GTN) and histamine causes an immediate headache dur ing the infusion and a genuine migraine attack one to several hours af ter the infusion. This identical time profile indicates a common mecha nism of action. To evaluate whether GTN causes headache via liberation of histamine, we studied the effect of GTN 0.5 mu g . kg(-1). min(-1) for 20 min in seven migraine sufferers, once after pretreatment with the histamine-1 (H-1)-receptor blocker mepyramine (0.5 mg . kg(-1)) an d once without pretreatment. This mepyramine dose is known to complete ly abolish histamine-induced headache. After pretreatment with mepyram ine five patients experienced migraine, and without pretreatment six p atients did so. The median peak headache score was 7 on a 0-10 scale w ith and without mepyramine pretreatment. The arterial responses, evalu ated with transcranial Doppler, were also unaffected by the mepyramine pretreatment. Our results demonstrate that neither headache nor arter ial dilatation due to GTN infusion is caused by histamine release, In all likelihood the common mediator of migraine induction by GTN and hi stamine is nitric oxide.