Impact of the circadian clock on fibrinolysis and coagulation in healthy individuals and cardiovascular patients - A systematic review.

INTRODUCTION: Human body functions exhibit a circadian rhythm generated in peripheral cells and synchronized by the suprachiasmatic nucleus (SCN), which mostly is entrained by the daily light/dark cycles. Activity, meals and posture are capable of interfering with the endogenous circadian rhythm of coagulation parameters. An increasing number of human disorders show a circadian component, and epidemiological studies find cardiovascular events to peak in the morning hours. The aim was to review the circadian rhythms impact on fibrinolysis and coagulation in healthy individuals and cardiovascular patients. MATERIALS AND METHODS: A total number of 25 studies were identified where 8 enrolled cardiovascular patients with or without healthy individuals. Using a MeSH-search in MEDLINE PubMed. Only original peer-reviewed papers were included. RESULTS: Results showed substantial variance with respect to exhibition of circadian rhythms and/or peak/trough times. Circadian rhythms of fibrinolysis were less pronounced in cardiovascular patients than in healthy individuals with decreased levels in the morning hours compared to healthy inducing higher risk of blood clotting. CONCLUSIONS: Because of small studied group sizes and failure to control for entraining factors, larger studies are needed to fully establish the effects of the circadian rhythm on especially coagulation. The findings of chronobiologic rhythms in coagulation and fibrinolysis could suggest a need for a chrono-pharmacological approach when treating/preventing cardiovascular diseases.

Specialized Outpatient Clinic vs Stroke Unit for TIA and Minor Stroke: A Cohort Study.

Objective: To evaluate the effects of an outpatient clinic set-up for minor stroke/TIA using subsequent admission of patients at 'high risk' of re-stroke.Methods: A cohort study of all patients with suspected minor stroke/TIA seen in an outpatient clinic at Aarhus University Hospital, Denmark, between September 2013 and August 2014. Stroke patients were compared to historic (same hospital) and contemporary (another comparable hospital) matched, hospitalized controls on the non-prioritized outcomes: Length-of-stay, re-admissions, care quality (10 process-performance measures) and mortality. TIA patients were compared to contemporary matched, hospitalized controls.Following complete diagnostic work-up, patients with stroke/TIA were classified into 'low'/high risk' of re-stroke ≤7 days. RESULTS: We analyzed 1,076 consecutive patients of whom 253 (23.5%) were subsequently admitted to the stroke ward. Stroke/TIA was diagnosed in 215/171 patients, respectively. Fifty-six percent (121/215) of the stroke patients were subsequently admitted to the stroke ward. Comparison with the historic stroke cohort (n=191) showed a shorter acute hospital stay for the strokes (median 1 vs 3 days); adjusted length-of-stay ratio 0.49 (95% CI 0.33-0.71). Furthermore, 30-day readmission rate was 3.2% vs 11.6%; adjusted hazard ratio 0.23 (0.09-0.59); and care quality was higher with a risk ratio of 1.30 (1.15-1.47). The comparison of stroke and TIAs to contemporary controls showed similar results. Only one patient in the 'low risk' category and not admitted experienced stroke within 7 days (0.6%). CONCLUSIONS: An outpatient clinic set-up for patients with minor stroke/TIA yields shorter acute hospital stay, lower re-admissions rates, and better quality than hospitalization in stroke units. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that a neurovascular specialist driven outpatient clinic for minor stroke/TIA patients with the ability of subsequent admission is safe and yields shorter acute hospital stay, lower re-admissions rates, and better quality than hospitalization in stroke units.

Acute endovascular reperfusion treatment in patients with ischaemic stroke and large-vessel occlusion (Denmark 2011-2017).

BACKGROUND AND PURPOSE: Acute endovascular reperfusion treatment (aERT) of stroke patients with large-vessel occlusions is efficacious and safe according to several clinical trials. Data on outcome and safety of aERT in daily clinical routine are warranted and, in this study, we present national data from Denmark during 2011-2017. METHODS: National data for Denmark from 2011 to 2017 on all aERT procedures in patients with acute ischaemic stroke and computed tomography angiography/magnetic resonance angiography-verified large-vessel occlusion were derived from the Danish Stroke Registry, a national clinical quality registry to which reporting is mandatory for all hospitals treating stroke patients. Outcome (modified Rankin Scale score) after 3 months, including time of death, was assessed prospectively based on clinical examination or the Danish Civil Registration System. RESULTS: During the 7 years of observation, a total of 1720 patients were treated with aERT. The annual number of procedures increased from 128 in 2011 to 409 in 2017. The median age was 70 years, 58% were males and median National Institutes of Health Stroke Scale score at baseline was 16. Median time from symptom onset to groin puncture was 238 min with a decreasing trend during the years. Successful recanalization was reported in 1306 (76%) patients. At 3-month follow-up, an modified Rankin Scale score of 0-2 was reported in 46% of patients, whereas 14% of patients had died. CONCLUSION: Routine data on aERT in acute ischaemic stroke in Denmark from 2011 to 2017 suggest that the procedure is safe and efficacious.

Mechanical Thrombectomy with the Embolus Retriever with Interlinked Cages in Acute Ischemic Stroke: ERIC, the New Boy in the Class.

BACKGROUND AND PURPOSE: The Embolus Retriever with Interlinked Cages (ERIC) device is a novel stent retriever for mechanical thrombectomy. It consists of interlinked cages and could improve procedural benchmarks and clinical outcome compared with classic stent retrievers. This study compares the rates of recanalization, favorable clinical outcome, procedural adverse events, and benchmarks between the ERIC device and classic stent retrievers. MATERIALS AND METHODS: From 545 patients treated with thrombectomy between 2012 and 2015, 316 patients were included. The mean age was 69 ±13 years, the mean baseline NIHSS score was 17 ± 5, and 174 (55%) were men. The ERIC was used as the primary thrombectomy device in 59 (19%) patients. In a propensity score matched analysis including the NIHSS score, clot location, delay to groin puncture, neurointerventionalist, and anesthetic management, 57 matched pairs were identified. RESULTS: Patients treated with the ERIC device compared with classic stent retrievers showed equal rates of recanalization (86% versus 81%, P = .61), equal favorable 3-month clinical outcome (mRS 0-2: 46% versus 40%, P = .71), and procedural adverse events (28% versus 30%, P = 1.00). However, in patients treated with the ERIC device, thrombectomy procedures were less time-consuming (67 versus 98 minutes, P = .009) and a rescue device was needed less often (18% versus 39%, P = .02) compared with classic stent retrievers. CONCLUSIONS: Mechanical thrombectomy with the ERIC device is effective and safe. Rates of favorable procedural and clinical outcomes are at least as good as those with classic stent retrievers. Of note, the ERIC device might be time-saving and decrease the need for rescue devices. These promising results call for replication in larger prospective clinical trials.

Visual attention in posterior stroke and relations to alexia.

Impaired visual attention is common following strokes in the territory of the middle cerebral artery, particularly in the right hemisphere, while attentional effects of more posterior lesions are less clear. Commonly, such deficits are investigated in relation to specific syndromes like visual agnosia or pure alexia. The aim of this study was to characterize visual processing speed and apprehension span following posterior cerebral artery (PCA) stroke. In addition, the relationship between these attentional parameters and single word reading is investigated, as previous studies have suggested that reduced visual speed and span may explain pure alexia. Eight patients with unilateral PCA strokes (four left hemisphere, four right hemisphere) were selected on the basis of lesion location, rather than the presence of any visual symptoms. Visual attention was characterized by a whole report paradigm allowing for hemifield-specific measurements of processing speed and apprehension span. All patients showed reductions in visual span contralateral to the lesion site, and four patients showed bilateral reductions in visual span despite unilateral lesions (2L; 2R). Six patients showed selective deficits in visual span, though processing speed was unaffected in the same field (ipsi- or contralesionally). Only patients with right hemifield reductions in visual span were impaired in reading, and this could follow either right or left lateralized stroke and was irrespective of visual field impairments. In conclusion, visual span may be affected bilaterally by unilateral PCA-lesions. Reductions in visual span may also be confined to one hemifield, and may be affected in spite of preserved visual processing speed. Furthermore, reduced span in the right visual field seems to be related to reading impairment in this group, regardless of lesion lateralization.

The effect of pelvic floor muscle training on sexual function in men with lower urinary tract symptoms after stroke.

BACKGROUND: Erectile dysfunction and lower urinary tract symptoms (LUTS) are common sequelae in men after stroke. OBJECTIVE: The objective of this study was to evaluate the effect of pelvic floor muscle training (PFMT) on measured erectile function as an indicator of sexuality in men with LUTS after stroke. METHOD: A sample of 516 men with stroke was invited to participate in this single-blinded, randomized controlled trial according to in- and exclusion criteria. This resulted in 31 participants who were randomized to either a Treatment Group (n = 16) or a Control Group (n = 15). The intervention included 12♣weeks of PFMT. The effect was measured on the International Index of Erectile Function (IIEF-5) questionnaire. RESULTS: Thirty participants (median age: 68 years; interquartile range: 60-74 years) completed the study, 15 in each group. The results of the IIEF-5 sum score showed a significant improvement (P < 0.04) from pre-test to post-test in the Treatment Group, but not in the Control Group. Within pre-test and 6-month follow-up, the median sum score decreased in both groups, worsened in the Control Group [Treatment Group, 3 (17%) versus Control Group, 5 (31%)]. There were differences between the groups at post-test and at follow-up, but they were not statistically significant. CONCLUSION: The results showed that, as measured by erectile function in men with LUTS after stroke, PFMT may have short-term and long-term effect, although no statistically significant effect was demonstrated between the groups.

RAAS and stress markers in acute ischemic stroke: preliminary findings.

OBJECTIVES: Angiotensin II type 1 receptor blockade has neuroprotective effects in animal stroke models, but no effects in clinical stroke trials. We evaluated cerebral and peripheral changes in the renin angiotensin aldosterone system (RAAS) and stress responses in acute ischemic stroke patients. MATERIALS AND METHODS: Blood from a jugular and cubital vein was collected within 48 h of stroke onset, after 24 and 48 h, and renin, angiotensin I, angiotensin II, aldosterone, norepinephrine, epinephrine, and cortisol were measured. Post-stroke cubital vein samples were collected after 8 (4.7-10) months. RESULTS: The acute systolic blood pressure was significantly increased, 148 (141-168) vs 140 (130-147) mmHg post-stroke. Angiotensin I, renin and aldosterone levels were significantly lower, angiotensin II was unchanged, and ACE activity was higher in the acute phase compared to post-stroke. No differences in RAAS were detected between jugular and cubital plasma levels. Jugular venous plasma levels of epinephrine and cortisol were elevated in the acute phase compared to cubital levels (P < 0.05). CONCLUSION: Increased epinephrine and cortisol levels in the jugular vein blood may reflect a higher peripheral turnover. The observed changes in RAAS in the acute stroke phase are consistent with responses to increased blood pressure.

Thrombolysis outcomes in acute ischemic stroke patients with prior stroke and diabetes mellitus.

BACKGROUND: Patients with concomitant diabetes mellitus (DM) and prior stroke (PS) were excluded from European approval of alteplase in stroke. We examined the influence of DM and PS on the outcomes of patients who received thrombolytic therapy (T; data from Safe Implementation of Thrombolysis in Stroke-International Stroke Thrombolysis Register) compared to nonthrombolyzed controls (C; data from Virtual International Stroke Trials Archive). METHODS: We selected ischemic stroke patients on whom we held data on age, baseline NIH Stroke Scale score (NIHSS), and 90-day modified Rankin Scale score (mRS). We compared the distribution of mRS between T and C by Cochran-Mantel-Haenszel (CMH) test and proportional odds logistic regression, after adjustment for age and baseline NIHSS, in patients with and without DM, PS, or the combination. We report odds ratios (OR) for improved distribution of mRS with 95% confidence interval (CI) and CMH p value. RESULTS: Data were available for 29,500 patients: 5,411 (18.5%) had DM, 5,019 had PS (17.1%), and 1,141 (5.5%) had both. Adjusted mRS outcomes were better for T vs C among patients with DM (OR 1.45 [1.30-1.62], n = 5,354), PS (OR 1.55 [1.40-1.72], n = 4,986), or concomitant DM and PS (OR 1.23 [0.996-1.52], p = 0.05, n = 1,136), all CMH p < 0.0001. These are comparable to outcomes between T and C among patients with neither DM nor PS: OR = 1.53 (1.42-1.63), p < 0.0001, n = 19,339. There was no interaction on outcome between DM and PS with alteplase treatment (tissue plasminogen activator × DM × PS, p = 0.5). Age ≤80 years or >80 years did not influence our findings. CONCLUSIONS: Outcomes from thrombolysis are better than the controls among patients with DM, PS, or both. We find no statistical justification for the exclusion of these patients from receiving thrombolytic therapy.

Nitroglycerin provocation in normal subjects is not a useful human migraine model?

Provoking delayed migraine with nitroglycerin in migraine sufferers is a cumbersome model. Patients are difficult to recruit, migraine comes on late and variably and only 50-80% of patients develop an attack. A model using normal volunteers would be much more useful, but it should be validated by testing the response to drugs of known efficacy in acute migraine. Furthermore, treatment during headache rather than pretreatment is the most naturalist method. To fulfil these requirements we used continuous long-lasting infusion of glyceryl trinitrate (GTN) 0.2 microg kg-1 min-1 for 140 min and gave aspirin 1000 mg, zolmitriptan 5 mg or placebo to normal healthy volunteers. The design was double-blind, placebo-controlled three-way crossover. Our hypothesis was that these drugs would be effective in the treatment of the mild constant headache induced by long-lasting GTN infusion. The headaches did not fulfil the International Headache Society diagnostic criteria for migraine without aura. Moreover, there was no effect on headache of either zolmitriptan or aspirin. Thus our hypothesis was disproved and we conclude that our model is not valid for the testing of new acute antimigraine drugs. Our experiment suggests that headache caused by direct nitric oxide (NO) action in the continued presence of NO is very resistance to analgesics and to specific acute migraine treatments. This suggests that NO works very deep in the cascade of events associated with vascular headache, whereas tested drugs work higher in the cascade. The model suggested here should therefore be tested with other headache/migraine-provoking agents that supposedly work higher in the cascade of events. The need for human models persists, but the solution to this problem is still pending.

Calcitonin gene-related peptide (CGRP) levels during glyceryl trinitrate (GTN)-induced headache in healthy volunteers.

The role of nitric oxide (NO) in migraine has been studied in the experimental glyceryl trinitrate (GTN)-infusion headache model. We hypothesized that GTN-induced headache may activate the trigeminovascular system and be associated with increased levels of sensory neuropeptides, including calcitonin gene-related peptide (CGRP). CGRP, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY) and somatostatin plasma levels were measured before and after placebo/sumatriptan injection and during GTN-induced headache. Following a double-blind randomized cross-over design, 10 healthy volunteers received subcutaneous sumatriptan 6 mg or placebo. This was succeeded by 20 min of GTN (0.12 µg kg(-1) min(-1)) infusion. At baseline no subject reported headache (using verbal rating scale from 0 to 10) and the jugular CGRP-like immunoreactivity (-LI) level was 18.6 ± 2.5 pmol/l. After a 20-min intravenous infusion of GTN 0.12 µg kg(-1) min(-1), median peak headache intensity was 4 (range 2-6) (P < 0.05), while jugular CGRP-LI levels were unchanged (19.0 ± 2.8 pmol/l; P > 0.05). There were no changes in VIP-, NPY- or somatostatin-LI. In conclusion, the NO donor GTN appears not to induce headache via immediate CGRP release.

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. METHODS: In this double-blind, randomized and placebo-controlled, crossover study 15 migraineurs with migraine without aura were pre-treated with 150 mg of prednisolone or placebo followed by a 20-min infusion of GTN (0.5 ug/kg/min). One hour after the GTN-infusion, the participants were sent home, but continued to rate headache and possible associated symptoms by filling out a headache diary every hour for 12 h. There were two equal primary efficacy end-points: frequency of delayed migraine and intensity of delayed headache. RESULTS: Nine patients experienced a GTN headache fulfilling the diagnostic criteria for migraine without aura on the placebo day compared with four patients on the prednisolone day (P = 0.14). Prednisolone pre-treatment did not alter the summed or peak immediate headache responses to GTN significantly (P = 0.08, P = 0.07), whereas the peak headache scores during the following 12 h were significantly lower after prednisolone pre-treatment (median peak score = 1, range 0-8) compared with placebo (median = 4, range 0-8) (P < 0.01). There was no difference between the two treatment days in the effect of GTN on blood flow velocity of the middle cerebral artery (a decrease) or on the dilation of the superficial temporal artery or the radial artery. CONCLUSION: Pre-treatment with prednisolone did not reduce the immediate GTN-induced headache, did not inhibit the frequency of delayed headache but significantly decreased the intensity of delayed GTN-induced headache. These findings suggest that GTN causes induction of inflammatory mediators, and that this is the mechanism of delayed GTN-induced migraine. They also support a role of inflammatory mediators in spontaneous migraine attacks.

Delayed migraine-like headache in healthy volunteers after a combination of acetazolamide and glyceryl trinitrate.

Glyceryl trinitrate (GTN) is a pro-drug dissociating nitric oxide throughout the body. It dilates cephalic arteries without increasing cerebral blood flow (CBF). GTN induces headache in healthy volunteers and migraine attacks in migraineurs. Acetazolamide (Az) increases CBF but does not dilate cerebral arteries. The hypothesis tested here was that Az, by dilating cerebral arterioles but not arteries and thereby decreasing pulsatile stretching of the wall of the large arteries and their perivascular sensory nerves, would reduce or prevent the GTN-induced headache We tested this hypothesis in 14 healthy volunteers. In a randomized, double-blind, cross-over study, they were pretreated with Az or placebo followed on both study days by a GTN infusion of 0.5 microg kg(-1) min(-1) for 20 min. Headache was scored on a verbal rating scale and a headache diary was kept for 12 h. Mean blood velocity of the middle cerebral artery was measured (transcranial Doppler). Our hypothesis was disproved, as Az did not decrease GTN-induced headache. Unexpectedly but interestingly, GTN combined with Az induced more delayed headache than GTN alone. Furthermore, a migraine-like headache was observed in three volunteers, who did not develop migraine after GTN alone. The fact that a suitable pharmacological intervention may trigger migraine in individuals with no prior migraine may suggest that the ability to develop migraine without aura is a quantitative genetic trait.

Lack of effect of norepinephrine on cranial haemodynamics and headache in healthy volunteers.

Stress is a provoking factor for both tension-type headache and migraine attacks. In the present single-blind study, we investigated if stress induced by norepinephrine (NE) could elicit delayed headache in 10 healthy subjects and recorded the cranial arterial responses. NE at a dose of 0.025 microg kg(-1) min(-1) or placebo was infused for 90 min and the headache was followed for 14 h. Blood flow velocity in the middle cerebral artery (measured with transcranial Doppler) and diameters of the temporal artery and the radial artery (measured with ultrasound) were followed for 2 h. There were no changes in these arterial parameters after NE. In both treatment groups three subjects developed delayed headaches. Thus, stress by NE infusion did not result in delayed headache.

Involvement of calcitonin gene-related peptide in migraine: regional cerebral blood flow and blood flow velocity in migraine patients.

Calcitonin gene-related peptide (CGRP)-containing nerves are closely associated with cranial blood vessels. CGRP is the most potent vasodilator known in isolated cerebral blood vessels. CGRP can induce migraine attacks, and two selective CGRP receptor antagonists are effective in the treatment of migraine attacks. It is therefore important to investigate its mechanism of action in patients with migraine. We here investigate the effects of intravenous human alpha-CGRP (halphaCGRP) on intracranial hemodynamics. In a double-blind, cross-over study, the effect of intravenous infusion of halphaCGRP (2 mug/min) or placebo for 20 min was studied in 12 patients with migraine without aura outside attacks. Xenon-133 inhalation SPECT-determined regional cerebral blood flow (rCBF) and transcranial Doppler (TCD)-determined blood velocity (V (mean)) in the middle cerebral artery (MCA), as well as the heart rate and blood pressure, were the outcome parameters. No change of rCBF was observed at the end of infusion [1.2% +/- 1.7 with halphaCGRP, vs. -1.6% +/- 3.1 with placebo (mean +/- SD)] (P = 0.43). V (mean) in MCA decreased to 13.5% +/- 3.6 with halphaCGRP versus 0.6% +/- 1.8 with placebo (P < 0.005). Since rCBF was unchanged, this indicates a dilation of the MCA. halphaCGRP induced a decrease in MAP (12%) (P < 0.005) and an increase in heart rate (58%) (P < 0.0001). CGRP dilates cerebral arteries, but the effect is so small that it is unlikely to be the only mechanism of CGRP-induced migraine.

Intracranial hemodynamics during intravenous infusion of glyceryl trinitrate.

The mechanisms of glyceryl trinitrate (GTN)-induced headache are not fully elucidated. In this study we administered GTN 0.5 microg/kg/min i.v. for 20 min in six healthy volunteers. Before, during and 60 min after the infusion, we investigated regional cerebral blood flow (rCBF), cerebral blood volume (CBV), both estimated with SPECT, and blood flow velocity (BFV) in the middle cerebral artery (MCA), measured with transcranial Doppler. Headache was scored on a numerical verbal rating (0-10) scale. rCBF was unchanged, CBV was slightly increased (13%) during GTN infusion, whereas BFV decreased both during (20%) and 60 min (15%) after GTN. Headache was short-lived and maximal during infusion. This discrepancy of time-effect curves for the effect of GTN on headache and dilatation of MCA indicates that MCA is most likely not the primary source of pain in GTN-induced headache. The time-effect curves for the effect of GTN on headache and on dilation of MCA differed markedly. This indicates that MCA is most likely not the primary source of pain in GTN-induced headache.

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 effect of propranolol on glyceryltrinitrate-induced headache and arterial response.

Prophylactic drug trials in migraine are long-lasting and expensive and require long-term toxicology information. A human migraine model would therefore be helpful in testing new drugs. Immediate headache and delayed migraine after glyceryltrinitrate (GTN) has been well characterized. We have recently shown that sodium valproate has prophylactic effect in the GTN model. Here we report our experience with propranolol in this model. Nineteen subjects with migraine without aura and 16 sex- and aged-matched healthy subjects were included in a two-centre randomized double-blind cross-over study. Fourteen migraine subjects and 14 healthy subjects completed the study and results from comparison of the 28 subjects are reported. Randomly propranolol 160 mg or placebo were each given daily for 14 days to both migraine and healthy subjects. A 20-min intravenous infusion of GTN 0.25 microg/kg per min was administered on a study day at the end of both pretreatment periods. Headache was registered for 12 h after GTN infusions. Its intensity was scored on a numerical verbal rating scale from 0 to 10. Fulfilment of International Headache Society (HIS) criteria was recorded for 24 h. Radial and superficial temporal artery diameters and blood velocity of both middle cerebral arteries were measured. All migraine subjects developed headache after GTN. No reduction of overall peak headache was found after propranolol (median 5, range 0-7) compared with placebo (median 5, range 0-10) (P = 0.441). Eight of the 14 completing migraine subject developed IHS 1.1 migraine after GTN, two subjects on both days, three subjects only after placebo, and three subjects only after propranolol. No reduction of GTN-induced migraine was found after propranolol compared with placebo (5 vs. 5, P = 1.000). All healthy subjects developed headache after GTN. No reduction of overall peak headache was found after propranolol (median 2, range 1-5) compared with placebo (median 1, range 1-7) (P = 0.315). Two subjects fulfilled IHS criteria 1.1 for migraine without aura after propranolol but not after placebo. The fulfilment was short lasting and did not require rescue medication. Headache after GTN was more pronounced in migraine subjects than in healthy subjects both with (P = 0.003) and without pretreatment with propranolol (P = 0.017). We found that 2 weeks of propranolol constricted the radial artery in healthy subjects but not in migraine subjects. GTN-induced vasodilatation abolished this difference. Mean maximum blood flow velocity in the middle cerebral artery was higher in healthy subjects than in migraine patients (P = 0.003-0.033) and unaffected by propranolol. We observed no effect of propranolol on GTN-induced headache and migraine. This could indicate that GTN induces migraine at a deeper level of the pathophysiological cascade of migraine than the prophylactic effect of propranolol. Propranolol does not constrict cerebral arteries, which therefore cannot be part of its mechanism of action in migraine.

A double-blind study of SB-220453 (Tonerbasat) in the glyceryltrinitrate (GTN) model of migraine.

The need for experimental migraine models increases as therapeutic options widen. In the present study, we investigated SB-220453 for efficacy in the glyceryltrinitrate (GTN) human experimental migraine model. SB-220453 is a novel benzopyran compound, which in animal models inhibits neurogenic inflammation, blocks propagation of spreading depression and inhibits trigeminal nerve ganglion stimulation-induced carotid vasodilatation. We included 15 patients with migraine without aura in a randomized double-blind crossover study. SB-220453 40 mg or placebo was followed by a 20-min GTN infusion. Headache, scored 0-10, was registered for 12 h, and fulfillment of International Headache Society (IHS) criteria was recorded until 24 h. Four subjects had a hypotensive episode after SB-220453 plus GTN but none after GTN alone. The reaction was unexpected, since animal models and previous human studies had shown no vascular or sympaticolytic activity with SB-220453. The study was terminated prematurely due to this interaction. GTN was consistent in producing headache and migraine that resembled the patients' usual spontaneous migraine. Nine patients had GTN on both study days. Peak headache score showed a trend towards reduction after SB-220453 compared with placebo (median 4 vs. 7, P = 0.15). However, no reduction was seen in the number of subjects experiencing delayed headache (8 vs. 8), number of subjects reporting migraine (6 vs. 8), migraine attacks fulfilling IHS criteria 1.1 or 1.7 (6 vs. 7) or IHS 1.1 alone (4 vs. 5). SB-220453 had no significant pre-emptive anti-migraine activity compared with placebo in this human model of migraine. Interaction between SB-220453 and GTN was discovered. This is important for the future development of the compound and underlines the usefulness of experimental migraine models.

The prophylactic effect of valproate on glyceryltrinitrate induced migraine.

In this study the human glyceryltrinitrate (GTN) model of migraine was for the first time used to test the effect of a prophylactic drug. We chose to test valproate due to its well documented effect as a migraine prophylactic drug. Efficacy of this compound would support the usefulness of the model in prophylactic antimigraine drug development. Twelve patients with migraine without aura were included in a randomized double blind crossover study. Valproate 1000 mg or placebo was given daily, each for a minimum of 13 days. On the last treatment day of each arm a 20 min intravenous infusion of GTN (0.25 microg/kg/min) was given. Headache was registered for 12 h after the infusion and headache intensity was scored on a scale from 0 to 10. Fulfillment of IHS criteria was recorded for 24 h. The middle cerebral arteries were evaluated by transcranial Doppler and the diameter of the superficial temporal and radial arteries were measured with high frequency ultrasound. GTN evoked migraine fulfilling IHS criteria 1.1 in 6 patients after placebo and in 2 patients after valproate (P = 0.125). Including additionally 3 patients on placebo and 1 patient on valproate who felt they had suffered a migraine attack, but who had as associated symptoms only photophobia or phonophobia, a significant reduction in the number of patients with induced migraine after valproate was seen (P = 0.031). Median peak headache intensity was 1 (range 0-9) after valproate compared to 4.5 (range 0-8) after placebo (P = 0.120). Pretreatment with valproate as compared to placebo reduced the velocity in both middle cerebral arteries after GTN (left P = 0.021, right P = 0.031). No effect of valproate was seen in the diameter of the superficial temporal artery (P = 0.781) or the radial artery (P = 0.367) before or after GTN. The study indicates that a prophylactic effect of valproate may be demonstrated using the GTN human migraine model. Although, all headache parameters were reduced after valproate compared to placebo, only one parameter was statistically significantly reduced probably because of the small number of patients. The size of the effect was similar to that of valproate in clinical trials. The GTN model may therefore be a valid tool for testing new prophylactic antimigraine drugs.

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 microg/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.