Lisbeth Hjorth Lassen

The CGRP-antagonist, BIBN4096BS does not affect cerebral or systemic haemodynamics in healthy volunteers

BIBN4096BS is a CGRP-antagonist effective in the treatment of migraine. Blocking the receptor of a strong vasodilator involves a theoretical risk of causing cerebral vasoconstriction, a probability not previously investigated with BIBN4096BS. Seven healthy volunteers completed this double-blinded placebo-controlled crossover study. The volunteers received randomly 10 min infusions of either placebo, 2.5 mg or 10 mg of BIBN4096BS on 3 separate days. Transcranial Doppler was used to measure the middle cerebral artery blood flow velocity (VMCA); global and regional cerebral blood flow (rCBFMCA) was measured by 133-Xenon inhalation SPECT. The diameter of the temporal and radial artery was measured by highresolution ultrasound. Systemic haemodynamics and partial pressure of CO2 (PetCO2), and adverse events were monitored regularly. BIBN4096BS had no influence on global or regional cerebral blood flow, or on the blood flow velocity in the middle cerebral artery. There was no effect on systemic haemodynamics and adverse events were minor. We conclude that there is no effect of CGRP-receptor blockade on the cerebral or systemic circulation in humans. Circulating CGRP is therefore not likely to exert a vasodilatory activity in the resting state and the use of BIBN4096BS for acute migraine seems to be without risk of cerebral vasoactivity. These data suggest that BIBN4096BS is the first specific antimigraine drug without vasoactive effect.

Histamine induces migraine via the H1-receptor. Support for the NO hypothesis of migraine

IN primates, histamine activates cerebral endothelial H1-receptors leading to formation of nitric oxide (NO). Twenty migraine patients received pretreatment with placebo or the histamine-H1-receptor antagonist, mepyr-amine, in a randomized, double blind fashion, followed in both groups by i.v. histamine (0.5μgkg-1 min-1 for 20min). Headache characteristics were subsequently observed for 12 h. In patients given placebo histamine caused immediate headache during the infusion followed by a delayed migraine attack fulfilling IHS criteria for migraine without aura. The temporal profile of induced headache was exactly the same as after glyceryl trinitrate. Mepyramine pretreatment abolished both immediate headache and delayed migraine attacks. Our results suggest that a migraine attack can be caused by NO formation in the endothelium of cerebral arteries.

The effect of nitric oxide synthase inhibition on histamine induced headache and arterial dilatation in migraineurs

We have previously proposed that histamine causes migraine via increased NO production. To test this hypothesis, we here examined if the NOS inhibitor, L-NG methylarginine hydrochloride (L-NMMA:546C88), could block or attenuate histamine induced migraine attacks and responses of the middle cerebral, temporal and radial arteries. In a double blind crossover design 12 patients were randomized to receive pretreatment with L-NMMA (6 mg/kg) or placebo i.v. over 15 min followed on both study days by histamine (0.5 μg/kg/min) i.v. for 20 min. Headache scores, mean maximal blood velocity (Vmean) in the middle cerebral artery (MCA) (transcranial doppler) and diameters of temporal and radial arteries (high resolution ultrasound) were repeatedly measured. Pre-treatment with L-NMMA, had no effect on histamine induced headache or migraine, but also had no effect on the magnitude of histamine induced – decrease in MCA blood velocity, or dilatation of neither the temporal nor the radial artery. L-NMMA constricted the temporal artery by 8% before histamine infusion, whereas the radial artery was unaffected. The temporal artery dilated 4-5 times more than the radial artery during histamine infusion. In conclusion the use of a NOS inhibitor in the highest possible dose did not block the histamine-induced headache response or arterial dilatation. Either the concentration of L-NMMA reaching the smooth muscle cell was insufficient or, histamine dilates arteries and causes headache via NO independent mechanisms. Our results showed for the first time a craniospecificity for the vasodilating effect of histamine and for the arterial effects of NOS inhibition.

Dipyridamole Dilates Large Cerebral Arteries Concomitant to Headache Induction in Healthy Subjects

Dipyridamole is used for secondary prophylaxis in ischemic stroke and as a vasodilator agent in myocardial scintigraphy. An important side effect to administering dipyridamole is headache. The aim of the current study was to investigate the effects of dipyridamole on cerebral blood flow, large artery diameter, and headache induction. Twelve healthy subjects were included in this single-blind placebo-controlled study in which placebo (0.9% NaCl) and dipyridamole 0.142 mg/kg·min were administered intravenously over 4 minutes 1 hour apart. Blood flow velocity in the middle cerebral artery (Vmca) was recorded by transcranial Doppler and regional cerebral blood flow in the middle cerebral artery (rCBFmca) was measured using single photon emission computed tomography and 133Xenon-inhalation. Blood pressure, heart rate, and pCO2 were measured repeatedly. Headache response was scored every 10 minutes on a verbal scale from 0 to 10 (10 = worst). Dipyridamole caused a decrease in pCO2 (P < 0.001). pCO2 corrected rCBFmca was 41.7 ± 6.9 mL/100 g ·min after placebo versus 41.2 ± 6.9 after dipyridamole (P ≥ 0.05). pCO2 corrected Vmca decreased 8.4% ± 11.7 (P < 0.001) after dipyridamole, indicating a mean 5.6% ± 6.7 (P = 0.005) relative increase of the arterial diameter. After dipyridamole the median peak headache score was 2 (range 0 to 7) compared with 0 (range 0 to 3) after placebo (P = 0.02). Dilatation of the middle cerebral artery outlasted the headache response. In conclusion, dipyridamole causes a modest pCO2 independent dilatation of the MCA, which is time-linked to the onset, but not to the cessation, of headache.

Role of endothelium and nitric oxide in histamine‐induced responses in human cranial arteries and detection of mRNA encoding H1‐ and H2‐receptors by RT‐PCR

Histamine induces relaxation of human cranial arteries. Studies have revealed that the relaxant histamine H1‐receptor predominates in human cerebral and the H2‐receptor in temporal arteries, while H1‐ and H2‐receptors are of equal importance in the middle meningeal artery. The purpose of the present study was to examine the role of the endothelium and nitric oxide in histamine‐induced responses and to show the presence of mRNA encoding H1‐ and H2‐receptors in human cranial arteries. Electrophoresis of polymerase chain reaction (PCR) products from human cerebral, middle meningeal and temporal arteries, demonstrated products corresponding to mRNA encoding both H1‐ and H2‐receptors in arteries with and without endothelium. The amplified PCR products were sequenced and showed 100% homology with the published sequences of these histamine receptors. A sensitive in vitro system was used to study vasomotor responses to histamine. In precontracted cerebral, middle meningeal and temporal arteries with and without endothelium, histamine caused a concentration‐dependent relaxation with Imax values between 87% and 81% and pIC50 values between 8.14 and 7.15. In arteries without endothelium the histamine‐induced relaxation was significantly less potent (Imax values between 87% and 66% and pIC50 values between 7.01 and 6.67) than in cranial arteries with an intact endothelium. The addition of histamine to arteries without endothelium and pretreated with the histamine H2‐antagonist, cimetidine (10−5 M), caused a concentration‐dependent contraction of the cranial arteries with Emax values between 86% and 29% and pEC50 values between 7.53 and 6.77. This contraction was blocked by the histamine H1‐receptor antagonist, mepyramine (10−7 M), and even turned into a relaxation with Imax values between 84% and 14% and pIC50 values between 7.42 and 5.86. The nitric oxide synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 3×10−5 M) significantly inhibited the relaxant response to histamine in cerebral and temporal arteries (pIC50 values between 7.43 and 7.13). The combined treatment with L‐NAME (3×10−5 M) and cimetidine (10−5 M) caused a further displacement of the concentration‐response curve (pIC50 values between 7.14 and 6.57) and decreased the maximum relaxant responses in all three cranial arteries (Imax values between 62% and 39%). In conclusion, this is the first study which show mRNA encoding histamine H1‐ and H2‐receptors in human cranial arteries. The results indicate that histamine‐induced relaxation of human cranial arteries is partially mediated via an endothelial H1‐receptor coupled to the production of nitric oxide and partially via a H2‐receptor associated with the smooth muscle cells. In addition, there is evidence for a contractile H1‐receptor in the smooth muscle cells in these arteries.

Histamine-1 receptor blockade does not prevent nitroglycerin induced migraine

It has previously been shown that in migraine sufferers infusion of glyceryl trinitrate (GTN) and histamine causes an immediate headache during the infusion and a genuine migraine attack one to several hours after the infusion. This identical time profile indicates a common mechanism of action. To evaluate whether GTN causes headache via liberation of histamine, we studied the effect of GTN 0.5 ώg · kg−1·min−1 for 20 min in seven migraine sufferers, once after pretreatment with the histamine-1(H1)-receptor blocker mepyramine (0.5 mg · kg−1) and once without pretreatment. This mepyramine dose is known to completely abolish histamine-induced headache. After pretreatment with mepyramine five patients experienced migraine, and without pretreatment six patients did so. The median peak headache score was 7 on a 0–10 scale with and without mepyramine pretreatment. The arterial responses, evaluated with transcranial Doppler, were also unaffected by the mepyramine pretreatment. Our results demonstrate that neither headache nor arterial dilatation due to GTN infusion is caused by histamine release. In all likelihood the common mediator of migraine induction by GTN and histamine is nitric oxide.

Dipyridamole may induce migraine in patients with migraine without aura

Dipyridamole inhibits phosphodiesterase 5 (PDE5) and adenosine re-uptake. The most prominent side-effect is headache. We examined the migraine-generating effects of dipyridamole as well as the cerebral blood velocity response in a single-blind study, including 10 patients with migraine without aura and 10 healthy subjects. Dipyridamole 0.142 mg/kg per min was administered intravenously. Headache intensity was scored on a verbal rating scale along with pain characteristics and accompanying symptoms. Blood velocity in the middle cerebral artery (V mca), blood pressure and heart rate were recorded repeatedly. Headache was induced in all migraine patients and in eight of 10 healthy subjects (P = 0.47) with no significant difference in headache intensity (P = 0.53). However, five patients but only one healthy subject experienced the symptoms of migraine without aura, according to ICHD-2 criteria, within 12 h (P = 0.14). Four patients reported photophobia after dipyridamole compared with no healthy subjects (P = 0.087). V mca decreased (P < 0.001) during and after dipyridamole infusion with no difference between groups (P = 0.15) coinciding with initiation, but not cessation of immediate headache. Thus, dipyridamole induces symptoms of migraine and an initial decrease in V mca in migraine patients, but not significantly more than in healthy subjects. This relatively low frequency of migraine induction, compared with nitric oxide donors and sildenafil, is probably due to the less specific action of dipyridamole on the cGMP signalling pathway as well as a possible bidirectional effect of adenosine on migraine induction.

The Role of Nitric Oxide in Migraine Pain

SummaryIn recent years, an increasing volume of evidence has suggested that the small messenger molecule nitric oxide (NO) plays a pivotal role in migraine pain. This evidence is mainly based on experimental studies using 2 different human headache models — intravenous infusion of nitroglycerin (glyceryl trinitrate) [a donor of NO] and intravenous infusion of histamine (which probably activates endothelial NO formation). These models offer unique possibilities for the study of NO mechanisms in migraine. Data suggest that NO is involved in the aetiology of migraine, a finding that may open up a number of possibilities for future drug treatments of the disorder.

Prednisolone reduces nitric oxide-induced migraine

Background and purpose  Glyceryl trinitrate (GTN) induces delayed migraine attacks in migraine patients. The purpose of this study was to investigate whether pre‐treatment with prednisolon could decrease this effect of GTN.

The effect of i.v. L-NG methylarginine hydrochloride (L-NMMA: 546C88) on basal and acetazolamide (Diamox) induced changes of blood velocity in cerebral arteries and regional cerebral blood flow in man.

The aim of this study was to estimate the effect of Nitric Oxide synthase (NOS)-inhibition (L-NMMA) on the diameter of the middle cerebral artery (MCA) and on regional cerebral blood flow (rCBF). Furthermore, to assess the effect of L-NMMA on acetazolamide induced increases in MCA blood velocity (Vmean) and rCBF. In an open crossover design 12 healthy subjects attended the laboratory twice. The first day 6 mg/kg L-LNMMA i.v. over 15 min preceded 1 g acetazolamide iv over 5 min. Eight days later only acetazolamide was given. Vmean in MCA was determined with transcranial Doppler (TCD) and rCBF with Xe-133 inhalation SPECT at baseline, after L-NMMA and 25 and 55 min after acetazolamide infusion. After L-NMMA the decrease in rCBFMCA was 6.8% (± 7.4) (P < 0.019, n = 12), whereas Vmean was not affected (P = 0.83, n = 8). The change in MCA diameter was estimated to -1.3% (P = 0.44, n = 8). L-NMMA did not affect acetazolamide increases in Vmean (P = 0.67, n = 8) nor rCBF (P = 0.29, n = 12). The percentage increase of Vmean was 1.5 times that of rCBF (n = 8). Our data suggest that the basal tone of human cerebral arterioles but not of conduit arteries is NO-dependent. The action of acetazolamide in man is not NO-dependent.