Prostacyclin (epoprostenol) induces headache in healthy subjects

An exploratory study evaluating the 30 medications most commonly associated with headaches in the FDA Adverse Event Reporting System

OBJECTIVE

This project seeks to identify the top 30 drugs most commonly associated with headaches in the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS), as well as their respective reporting odds ratios (RORs).

BACKGROUND

Headache secondary to medication use is a well-known entity. However, which medications are most likely to cause headaches on a global scale is unknown.

METHODS

We extracted case identifiers, adverse events, and attributed medications for entries in the FAERS database from July 1, 2018, to March 31, 2020. Entries were split into two datasets based on whether or they contained the word "headache(s)." Non-medication words were then excluded. The medications most commonly associated with headaches were then identified.

RESULTS

We extracted 2,673,081 entries, of which 86,086 contain the word "headache(s)." The 30 most frequently appearing medications were then ranked by ROR values with associated 95% confidence intervals. The three medications with the greatest association with headaches were selexipag (ROR 16.7, 95% CI 15.8-17.7), epoprostenol (ROR 11.7, 95% CI 10.8-12.7), and glecaprevir (ROR 8.7, 95% CI 8.3-9.2). Immunosuppressants, antivirals, as well as pulmonary hypertension medication classes were most commonly associated with headache.

CONCLUSION

Our study offers a potential list of the medication classes commonly associated with iatrogenic headaches.

Arterial responses to infusion of glucagon-like peptide-1 in humans: A randomized trial study

Glucagon-like-peptide-1 (GLP-1) is an incretin hormone implicated in several metabolic and neurological disorders. GLP-1 induces vasodilation and increases blood flow in the peripheral circulation. Whether GLP-1 alters cerebral hemodynamics in humans is yet to be elucidated. In a crossover, double-blind, placebo-controlled, and randomized design, 21 healthy volunteers were assigned to receive intravenous GLP-1 infusion (2.5 pmol/kg/min) or placebo over 20 min on two different days separated by at least one week. We used a noninvasive, well-validated transcranial doppler (TCD) and ultrasound dermascan to reveal the effect of GLP-1 on intra- and extracerebral arteries. The mean blood flow velocity in the middle cerebral artery (V_MCA), the diameter of the superficial temporal artery (STA) and radial artery (RA), and facial skin blood flow were measured. In addition, we documented headache and its associated symptoms during and after infusion. Twenty participants were included in the final analysis. We found no difference in the V_MCA (P = 0.227), diameter of the STA (P = 0.096) and the RA (P = 0.221) and facial blood flow (P = 0.814) after GLP-1 compared to placebo. There were no differences in HR, SAT, EtCO₂, or RF (P > 0.05) on the GLP-1 day compared to the placebo day. We found no differences in the incidence of headache after GLP-1 (n = 10) compared to placebo (n = 7) (P = 0.250). GLP-1 infusion did not affect cerebral hemodynamics and induce headache in humans. Further preclinical studies with validated methods are required to determine if intra - and extracerebral vasculature express GLP-1Rs in humans.

Changes in Plasma Lipid Levels Following Cortical Spreading Depolarization in a Transgenic Mouse Model of Familial Hemiplegic Migraine

Metabolite levels in peripheral body fluids can correlate with attack features in migraine patients, which underscores the potential of plasma metabolites as possible disease biomarkers. Migraine headache can be preceded by an aura that is caused by cortical spreading depolarization (CSD), a transient wave of neuroglial depolarization. We previously identified plasma amino acid changes after CSD in familial hemiplegic migraine type 1 (FHM1) mutant mice that exhibit increased neuronal excitability and various migraine-related features. Here, we aimed to uncover lipid metabolic pathways affected by CSD, guided by findings on the involvement of lipids in hemiplegic migraine pathophysiology. Using targeted lipidomic analysis, we studied plasma lipid metabolite levels at different time points after CSD in wild-type and FHM1 mutant mice. Following CSD, the most prominent plasma lipid change concerned a transient increase in PGD₂, which lasted longer in mutant mice. In wild-type mice only, levels of anti-inflammatory lipid mediators DPAn-3, EPA, ALA, and DHA were elevated 24 h following CSD compared to Sham-treated animals. Given the role of PGs and neuroinflammation in migraine pathophysiology, our findings underscore the potential of monitoring peripheral changes in lipids to gain insight in central brain mechanisms.

Assessment of peripheral biomarkers potentially involved in episodic and chronic migraine: a case-control study with a focus on NGF, BDNF, VEGF, and PGE2

Background

Several inflammatory and vascular molecules, and neurotrophins have been suggested to have a possible role in the development of migraine. However, pathophysiological events leading to migraine onset and transformation of episodic migraine (EM) to chronic migraine (CM) are not fully understood. Thus, we aimed to assess peripheral levels of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in EM and CM patients, and controls.

Methods

From September 2017 to June 2020, 89 subjects were enrolled in a case-control study; 23 and 36 EM and CM patients, respectively, and 30 age and sex-matched controls. Demographic data and medical history were obtained from all patients. Headache characteristics were recorded at baseline visit and ensuing 30 days for persons with migraine disease. Serum levels of NGF, BDNF, VEGF, and PGE2 were measured once for controls and EM and CM patients, and adjusted for age, sex, and body mass index.

Results

Serum levels of NGF were significantly lower in EM patients compared to controls and CM patients (P-value=0.003 and 0.042, respectively). Serum levels of BDNF were significantly lower in EM and CM patients as opposed to controls (P-value<0.001), but comparable between EM and CM patients (P-value=0.715). Peripheral blood levels of VEGF were significantly higher in EM and CM patients as opposed to controls (P-value<0.001), but not different between EM and CM patients (P-value=0.859). Serum levels of PGE2 were significantly lower in EM patients compared to controls (P-value=0.011), however similar between EM and CM patients (P-value=0.086). In migraine patients, serum levels of NGF and PGE2 positively correlated with headache frequency (NGF: ρ = 0.476 and P-value<0.001; PGE2: ρ = 0.286 and P-value=0.028), while corresponding levels of BDNF and VEGF did not correlate with headache frequency (BDNF: ρ = 0.037 and P-value=0.778; VEGF: ρ= -0.025 and P-value=0.850).

Conclusions

Our findings suggest that NGF, BDNF, PGE2, and VEGF may play a significant role in migraine pathogenesis and/or chronification, and therefore might bear potential value for novel targeted abortive and prophylactic migraine therapy. Further prospective cohort studies with larger sample sizes can more robustly evaluate the implications of these findings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-021-01377-6.

Headaches related to latanoprost in open-angle glaucoma

Clinical relevance: The existing notion that topical latanoprost can lead to symptoms of headaches by reporting three cases of headache symptoms that developed following instillation of latanoprost prescribed as first-line therapy for newly diagnosed primary open-angle glaucoma (POAG) is explored in this case series.Background: Prostaglandin analogues (PGAs) are often used as first-line treatment in the treatment of POAG. An uncommon and infrequently reported side effect of PGAs is headaches.Methods: A retrospective review of patient records was conducted on patients seen at the Centre for Eye Health between April 2016 and August 2017. Clinical findings, including outcomes following interventions such a punctal occlusion, as well as the proposed pharmacological mechanism underlying this phenomenon are presented and discussed.Results: Case 1 is a 62-year-old Caucasian male diagnosed with POAG and prescribed latanoprost in both eyes. At the follow-up visit, he reported waking up in with a dull throbbing headache following instillation of the eye drops the night before. Case 2 is a 58-year-old Asian male with POAG prescribed latanoprost to both eyes. Within a week, he developed symptoms of recurrent progressively worsening headaches post-instillation which persisted into the morning. Case 3 is a 75-year-old Caucasian male with POAG prescribed latanoprost for both eyes. He developed latanoprost sensitivity as well as headache symptoms associated with the eye drops which resolved followed its cessation. All patients reported initial symptoms of headaches associated with latanoprost use however the headaches were not persistent with intermittent punctal occlusion (cases 1 and 2) or intra-class drug rechallenge (case 3).Conclusion: Although there may be a yet-undiscovered link between a headache response and latanoprost, these cases call to question the pharmacological relationship between latanoprost and headache symptoms. A systemic approach to critically examine the pathophysiological link between pharmacological therapy and potential adverse effects is proposed.

Nocebo response in human models of migraine: A systematic review and meta-analysis of randomized, double-blind, placebo-controlled, two-way crossover trials in migraine without aura and healthy volunteers

BACKGROUND

Human models of migraine have been used for the past 30 years to test putative 'trigger' molecules and ascertain whether they induce migraine attacks in humans. However, nocebo effects using this model have never been systematically explored.

OBJECTIVE

To assess the nocebo response rate in randomised clinical trials conducted at the Danish Headache Center, and in which human models of migraine were used.

METHODS

In this systematic review and meta-analysis, we searched PubMed for studies of human models of migraine with a randomised, double-blind, placebo-controlled, two-way crossover design that included data on the incidence of migraine attacks or headache after infusion of placebo. A total of 943 articles were screened by title and abstract. Of these, 27 studies met the inclusion criteria (published between 1994 and 2020) and were included in the qualitative and quantitative analysis. We performed a random effects meta-analysis for the incidence of migraine attacks or delayed headache after placebo infusion.

RESULTS

Twenty-seven studies were eligible for inclusion: 12 studies reported data for adults with migraine (n = 182), whereas 16 studies reported data on healthy volunteers (n = 210). For adults with migraine, the incidence of migraine attacks after placebo was 8.1% (95% CI = 2.5-15.5%, I² = 50.8%). The incidence of delayed headache was 25.9% (95% CI = 18.5-34.1%, I² = 18.9%). For healthy volunteers, the incidence of migraine attacks after placebo was 0.5% (95% CI = 0.0-3.6%, I² = 0.0%) while the incidence of delayed headache was 10.5% (95% CI = 4.8-17.6%, I² = 45.2%).

CONCLUSION

The nocebo response in randomised, placebo-controlled two-way crossover trials with intravenous infusions of placebo in migraine is negligible. Future studies using human models of migraine can be conducted by assuming a nocebo response rate of 15.5%.

Exploration of candidate serum biomarkers potentially related to the chronic pain condition in Medication-overuse headache

Background

Medication Overuse Headache (MOH) is a prevalent and disabling disorder resulting from the overuse of analgesic drugs, triptans or other acute headache medications. In previous proteomic studies, several proteins have been found at high concentrations in the urine of MOH patients and in the serum of rats with neuropathic pain. The aim of this study was to compare the serum levels of lipocalin-type Prostaglandin D2 synthase (L-PGDS), Vitamin D-binding protein (VDBP), apolipoprotein E (APOE) and apolipoprotein A1 (APOA1) in MOH patients and healthy individuals, further exploring their relationship with cutaneous pain thresholds (CPTs) in the territories innervated by the trigeminal nerve.

Methods

Sixty-nine MOH patients and 42 age- and sex-matched healthy volunteers were enrolled in the study. Von Frey-like filaments were applied to the skin territories innervated by the trigeminal nerve, to determine the CPTs. L-PGDS, VDBP, APOE and APOA1 were quantified in the serum by Enzyme-linked Immunosorbent Assay (ELISA). Clinical and laboratory data were collected. Comparisons between MOH patients and healthy individuals were performed using independent t test or χ² test. To correlate serum proteins with CPTs, Pearson correlation coefficient or Spearman’s rank correlation coefficient were used.

Results

CPTs were lower among MOH patients. L-PGDS, VDBP and APOE had significantly different serum concentrations between groups (p < 0.01), but no correlation was found with CPTs. APOA1 serum concentrations did not differ between patients and healthy individuals.

Conclusions

L-PGDS, VDBP and APOE had abnormal serum levels in MOH patients, confirming their alteration in some conditions of chronic headache and neuropathic pain. However, they had no relationship with CPTs. The in-depth study of serum proteins represents a promising approach for a better understanding of MOH, as well as the detection of candidate biomarkers for chronic headache or the risks associated with overuse medications.

Migraine-provoking substances evoke periorbital allodynia in mice

Background

Administration of endogenous mediators or exogenous chemicals in migraine patients provoke early headaches and delayed migraine-like attacks. Although migraine provoking substances are normally vasodilators, dilation of arterial vessels does not seem to be the sole contributing factor, and the underlying mechanisms of the delayed migraine pain are mostly unknown. Sustained mechanical allodynia is a common response associated with the local administration of various proalgesic substances in experimental animals and humans. Here, we investigated the ability of a series of endogenous mediators which provoke or do not provoke migraine in patients, to cause or not cause mechanical allodynia upon their injection in the mouse periorbital area.

Methods

Mechanical allodynia was assessed with the von Frey filament assay. Stimuli were given by subcutaneous injection in the periorbital area of C57BL/6J mice; antagonists were administered by local and systemic injections.

Results

Calcitonin gene related peptide (CGRP), but not adrenomedullin and amylin, pituitary adenylyl cyclase activating peptide (PACAP), but not vasoactive intestinal polypeptide (VIP), histamine, prostaglandin E₂ (PGE₂) and prostacyclin (PGI₂), but not PGF_2α, evoked a dose-dependent periorbital mechanical allodynia. The painful responses were attenuated by systemic or local (periorbital) administration of antagonists for CGRP (CLR/RAMP1), PACAP (PAC-1), histamine H₁, PGE₂ (EP₄), and PGI₂ (IP) receptors, respectively.

Conclusions

The correspondence between substances that provoke (CGRP; PACAP, histamine, PGE₂, PGI₂), or do not provoke (VIP and PGF_2α), migraine-like attacks in patients and periorbital allodynia in mice suggests that the study of allodynia in mice may provide information on the proalgesic mechanisms of migraine-provoking agents in humans. Results underline the ability of migraine-provoking substances to initiate mechanical allodynia by acting on peripheral terminals of trigeminal afferents.

PACAP and its receptors in cranial arteries and mast cells

Background

In migraineurs pituitary adenylate cyclase activating peptide1–38 (PACAP1–38) is a potent migraine provoking substance and the accompanying long lasting flushing suggests degranulation of mast cells. Infusion of the closely related vasoactive intestinal peptide (VIP) either induces headache or flushing. This implicates the pituitary adenylate cyclase activating peptide type I receptor (PAC1) to be involved in the pathophysiology of PACAP1–38 provoked headaches. Here we review studies characterizing the effects of mainly PACAP but also of VIP on cerebral and meningeal arteries and mast cells.

Discussion

PACAP1–38, PACAP1–27 and VIP dilate cerebral and meningeal arteries from several species including man. In rat cerebral and meningeal arteries the dilation seems to be mediated preferably via vasoactive intestinal peptide receptor type 1 (VPAC1) receptors while, in human, middle meningeal artery dilation induced via vasoactive intestinal peptide receptor type 2 (VPAC2) receptors cannot be ruled out. PACAP1–38 is a strong degranulator of peritoneal and dural mast cells while PACAP1–27 and VIP only have weak effects. More detailed characterization studies suggest that mast cell degranulation is not mediated via the known receptors for PACAP1–38 but rather via a still unknown receptor coupled to phospholipase C.

Conclusion

It is suggested that PACAP1–38 might induce migraine via degranulation of dural mast cells via a yet unknown receptor.

Characterization of Prostacyclin-associated Leg Pain in Patients with Pulmonary Arterial Hypertension

RATIONALE

Prostacyclin-associated leg pain is a potentially debilitating adverse effect of prostacyclin therapy for patients with pulmonary arterial hypertension (PAH). However, to our knowledge, this entity has not been systematically studied.

OBJECTIVES

To characterize the clinical features and metabolic risk factors for prostacyclin-associated leg pain.

METHODS

At one academic medical center, we assembled and analyzed a case series of patients with PAH and prostacyclin-associated leg pain.

MEASUREMENTS AND MAIN RESULTS

Over a period of 2 years, we identified 11 patients with PAH and prostacyclin-associated leg pain who agreed to participate in this study. Subjects underwent a standardized clinical evaluation, electrodiagnostic assessment, and serologic screen for metabolic causes of peripheral neuropathy. All 11 patients were female; their mean (SD) age was 50 (±9) years; their median (interquartile range) PAH duration was 56 (20-96) months; and their prostacyclin therapy duration was a median (interquartile range) of 20 (14-36) months. All patients reported leg pain beginning soon after prostacyclin initiation and varying with dose. All described a neuropathic pain in a symmetric, distal, stocking distribution. Neurologic examination revealed a sensory, small-fiber, predominantly peripheral neuropathy in seven (78%) patients. Results of autonomic reflex testing and thermoregulatory sweat testing were abnormal in 82% and 90% of patients, respectively, suggesting small-fiber neuropathy. Serologic evaluation identified a new, previously unrecognized contributor to neuropathy in eight (73%) patients, including vitamin B₁₂ deficiency in six (55%), uncompensated hypothyroidism in three (27%), and diabetes mellitus in one (9%).

CONCLUSIONS

Chronic prostacyclin-associated leg pain is associated with a small-fiber neuropathy. Treatable metabolic contributors (vitamin B₁₂ deficiency, thyroid dysfunction, or diabetes) appear to be common possible "second hits" that may be underrecognized. We recommend screening for possible metabolic contributors in patients who have otherwise unexplained leg pain in the setting of PAH and current or anticipated prostacyclin therapy.

Human models of migraine - short-term pain for long-term gain

Migraine is a complex disorder characterized by recurrent episodes of headache, and is one of the most prevalent and disabling neurological disorders. A key feature of migraine is that various factors can trigger an attack, and this phenomenon provides a unique opportunity to investigate disease mechanisms by experimentally inducing migraine attacks. In this Review, we summarize the existing experimental models of migraine in humans, including those that exploit nitric oxide, histamine, neuropeptide and prostaglandin signalling. We describe the development and use of these models in the discovery of molecular pathways that are responsible for initiation of migraine attacks. Combining experimental human models with advanced imaging techniques might help to identify biomarkers of migraine, and in the ongoing search for new and better migraine treatments, human models will have a key role in the discovery of future targets for more-specific and more-effective mechanism-based antimigraine drugs.

Synthesis of both enantiomers of 1,2,3,4-tetrahydroisoquinoline derivative IPPAM-1 and enantio-dependency of its positive allosteric modulation of prostacyclin receptor

We present a practical synthesis of both enantiomers of 1,2,3,4-tetrahydroisoquinoline derivative IPPAM-1 (1), which is a positive allosteric modulator (PAM) of prostacyclin receptor (IP) and a candidate for treatment of pulmonary arterial hypertension without the side effects caused by IP agonists. Assay of cAMP production by CHO-K1 cells stably expressing human IP clearly demonstrated that the IPPAM activity resides exclusively on the R-form of 1.

A mesenteric traction syndrome affects near-infrared spectroscopy evaluated cerebral oxygenation because skin blood flow increases

During abdominal surgery manipulation of internal organs may induce a "mesenteric traction syndrome" (MTS) including a triad of flushing, hypotension, and tachycardia that lasts for about 30 min. We evaluated whether MTS affects near-infrared spectroscopy (NIRS) assessed frontal lobe oxygenation (S_cO₂) by an increase in forehead skin blood flow (SkBF). The study intended to include 10 patients who developed MTS during pancreaticoduodenectomy and 22 patients were enrolled (age 61 ± 8 years; mean ± SD). NIRS determined ScO₂, laser Doppler flowmetry determined SkBF, cardiac output (CO) was evaluated by pulse-contour analysis (Modelflow), and transcranial Doppler assessed middle cerebral artery mean flow velocity (MCA V_mean). MTS was identified by flushing within 60 min after start of surgery. MTS developed 20 min (12-24; median with range) after the start of surgery and heart rate (78 ± 16 vs. 68 ± 17 bpm; P = 0.0032), CO (6.2 ± 1.4 vs. 5.3 ± 1.1 L min^-1; P = 0.0086), SkBF (98 ± 35 vs. 80 ± 23 PU; P = 0.0271), and S_cO₂ (71 ± 6 vs. 67 ± 8%; P < 0.0001), but not MCA V_mean (32 ± 8 vs. 32 ± 7; P = 0.1881) were largest in the patients who developed MTS. In some patients undergoing abdominal surgery NIRS-determined S_cO₂ is at least temporarily affected by an increase in extra-cranial perfusion independent of cerebral blood flow as indicated by MCA V_mean. Thus, NIRS evaluation of S_cO₂ may overestimate cerebral oxygenation if patients flush during surgery.

Effect of PGD2 on middle meningeal artery and mRNA expression profile of L-PGD2 synthase and DP receptors in trigeminovascular system and other pain processing structures in rat brain

BACKGROUND

Prostaglandins (PGs), particularly prostaglandin D₂ (PGD₂), E₂ (PGE₂), and I₂ (PGI₂), are considered to play a role in migraine pain. In humans, infusion of PGD₂ causes lesser headache as compared to infusion of PGE₂ and PGI₂. Follow-up studies in rats have shown that infusion of PGE₂ and PGI₂ dilate the middle meningeal artery (MMA), and mRNA for PGE₂ and PGI₂ receptors is present in rat trigeminovascular system (TVS) and in the brain structures associated with pain. In the present study, we have characterized the dilatory effect of PGD₂ on rat MMA and studied the relative mRNA expression of PGD₂ receptors and lipocalin-type of PGD₂ synthase (L-PGDS).

METHOD

Rat closed-cranial window (CCW) model was used to study the effect of the DP₁ receptor antagonist, MK-0524, on PGD₂-induced vasodilation of middle meningeal artery. The qPCR technique was used for mRNA expression analysis.

RESULTS

PGD₂ infusion evoked a dose-dependent dilation of the rat MMA. The calculated mean pED₅₀ value was 5.23±0.10 and E_max was 103±18% (n=5). MK-0524 significantly (∼61%, p<0.05) blocked the PGD₂-induced dilation of MMA. mRNA for the DP₁, DP₂ and L-PGDS were expressed differentially in all tested tissues. DP₁ receptor mRNA was expressed maximally in trigeminal ganglion (TG) and in cervical dorsal root ganglion (DRG).

CONCLUSIONS

High expression of DP₁ mRNA in the TG and DRG suggest that PGD₂ might play a role in migraine pathophysiology. Activation of the DP₁ receptor in MMA was mainly responsible for vasodilation induced by PGD₂ infusion.

Expression of prostaglandin I2 (prostacyclin) receptor in blood of migraine patients: A potential biomarker

Background:

Migraine is the most common chronic neurological disorders that may be associated with vasodilatation. According to the role of prostaglandin I2 (prostacyclin) receptor (PTGIR) in migraine as a receptor, which acts in vasodilatation, we decided to study the changes of PTGIR expression in migraine patients in relation to a suitable control group.

Materials and Methods:

Extracted mRNA from lymphocytes of 50 cases and 50 controls was used to synthesize cDNA. Real-time polymerase chain reaction was performed, and the data were analyzed. Our results show that PTGIR mRNA expression in cases was significantly higher than the control group (P = 0.010).

Results:

In conclusion, mRNA expression of PTGIR in the blood of people with migraines could be considered as a biomarker.

Conclusion:

In addition, repression of PTGIR gene expression by methods such as using siRNA is probably suitable for therapy of migraine patients.

Prostaglandins in migraine: update

PURPOSE OF REVIEW

This review presents recent findings on the role of prostaglandins in migraine pathophysiology.

RECENT FINDINGS

Experimental studies have shown that prostaglandins are distributed in the trigeminal-vascular system and its receptors are localized in the trigeminal ganglion and the trigeminal nucleus caudalis. Prostaglandins were found in smooth muscles of cranial arteries, and functional studies in vivo showed that prostaglandins induced dilatation of cranial vessels. Human studies showed that intravenous infusion of vasodilating prostaglandins such as prostaglandin E₂ (PGE₂), prostaglandin I₂ (PGI₂) and prostaglandin D₂ (PGD₂) induced headache and dilatation of intra-cranial and extra-cranial arteries in healthy volunteers. In contrast, infusion of non-dilating prostaglandin F₂α (PGF₂α) caused no headache or any vascular responses in cranial arteries. PGE₂ and PGI₂ triggered migraine-like attacks in migraine patients without aura, accompanied by dilatation of the intra-cerebral and extra-cerebral arteries. A novel EP4 receptor antagonist could not prevent PGE₂-induced headache in healthy volunteers.

SUMMARY

Recent in-vitro/in-vivo data demonstrated presence and action of prostaglandins within the trigeminal pain pathways. Migraine induction after intravenous administration of PGE₂ and PGI₂ suggests a specific blockade of their receptors, EP and IP respectively, as a new potential drug target for the acute treatment of migraine.

Pearls and pitfalls in human pharmacological models of migraine: 30 years' experience

In vitro studies have contributed to the characterization of receptors in cranial blood vessels and the identification of new possible anti-migraine agents. In vivo animal models enable the study of vascular responses, neurogenic inflammation, peptide release and genetic predisposition and thus have provided leads in the search for migraine mechanisms. All animal-based results must, however, be validated in human studies because so far no animal models can predict the efficacy of new therapies for migraine.

Given the nature of migraine attacks, fully reversible and treatable, the headache- or migraine-provoking property of naturally occurring signaling molecules can be tested in a human model. If such an endogenous substance can provoke migraine in human patients, then it is likely, although not certain, that blocking its effect will be effective in the treatment of acute migraine attacks.

To this end, a human in vivo model of experimental headache and migraine in humans has been developed. Human models of migraine offer unique possibilities to study mechanisms responsible for migraine and to explore the mechanisms of action of existing and future anti-migraine drugs. The human model has played an important role in translational migraine research leading to the identification of three new principally different targets in the treatment of acute migraine attacks and has been used to examine other endogenous signaling molecules as well as genetic susceptibility factors. New additions to the model, such as advanced neuroimaging, may lead to a better understanding of the complex events that constitute a migraine attack, and better and more targeted ways of intervention.

Prostaglandin E(2) induces immediate migraine-like attack in migraine patients without aura

BACKGROUND

Prostaglandin E(2) (PGE(2)) has been suggested to play an important role in the pathogenesis of migraine. In the present experiment we investigated if an intravenous infusion of PGE(2) would induce migraine-like attacks in patients with migraine.

METHODS

Twelve patients with migraine without aura were randomly allocated to receive 0.4 µg/kg/min PGE(2) (Prostin(®)E2, dinoprostone) or placebo over 25 minutes in a two-way, crossover study. Headache intensity was recorded on a verbal rating scale, middle cerebral artery blood flow velocity (V(MCA)) was measured by transcranial Doppler (TCD) and diameter of the superficial temporal artery (STA) was obtained by c-series scan (Dermascan C).

RESULTS

In total, nine migraine patients (75%) experienced migraine-like attacks after PGE(2) compared to none after placebo (p = 0.004). Seven out of 9 (58%) patients reported the migraine-like attacks during the immediate phase (0-90 min) (p = 0.016). Only two patients experienced the delayed migraine-like attacks several hours after the PGE(2) infusion stop (p = 0.500). The V(MCA) decreased during the PGE(2) infusion (p = 0.005) but there was no significant dilatation of the STA (p = 0.850).

CONCLUSION

The migraine-like attacks during, and immediately after, the PGE(2) infusion contrast with those found in previous provocation studies, in which the other pharmacological compounds triggered the delayed migraine-like attacks several hours after the infusion. We suggest that PGE(2) may be one of the important final products involved in the generation of migraine attacks.

The role of the neurovascular scalp structures in migraine

AIM

To review reports suggesting a role for neurovascular scalp structures in migraine.

MAIN DATA REPORTED

(A) Scalp periarterial nervous fibres contain all the main peptides and receptors involved in pain. (B) It is possible to interrupt or alleviate migraine pain with a prolonged compression of the main scalp arteries, which decreases blood flow through the pain-sensitized vessels and probably induces a temporary conduction block of periarterial nociceptive fibres. (C) Painful points are present on the scalp arteries of a considerable percentage of migraine sufferers. (D) It is possible to stop or alleviate pain by intervening on nociceptive periarterial fibres, as for example with the injection of lidocaine or 3-5 ml saline, and with percutaneous application of a capsaicin cream.

CONCLUSION

The data reported suggest a role for neurovascular scalp structures in at least some patients with migraine. It would be of interest to find a clinical distinction between patients according to the prevalence of an intracranial or extracranial peripheral pain mechanism. This could lead to more efficacious treatments.

Pro-inflammatory and vasoconstricting prostanoid PGF2α causes no headache in man

Background: During two decades of migraine provocation studies with naturally occurring signalling molecules, vasodilators such as prostaglandin E2, prostaglandin I2 (prostacyclin) and prostaglandin D2 were shown to be able to induce headache in man. To elucidate the role of inflammation and vasodilatation in the generation of headache, we investigated whether the pro-inflammatory and vasoconstricting prostanoid prostaglandin F2α (PGF2α) would cause headache in a human model of headache.

Methods: Twelve healthy volunteers were randomly allocated to receive 3.5 µg/kg/min PGF2α or placebo over 20 min in a two-way crossover study. We recorded headache intensity on a verbal rating scale, middle cerebral artery blood flow velocity (VMCA) and the diameters of the superficial temporal artery (STA) and radial artery (RA).

Results: We found no difference in the area under the curve (AUC) for immediate headache (0–90 min) between PGF2α and placebo ( p = 0.144). The McNemar's test showed no difference in the incidence of immediate and delayed headache between verum and placebo ( p = 0.500 and p = 1.000, respectively). There was no difference in VMCA ( p = 0.776) and in the diameter of the STA ( p = 0.460) or RA ( p = 0.780) between PGF2α and placebo.

Conclusion: The present study shows that PGF2α, unlike vasodilating prostaglandins, does not provoke headache. We suggest that the vasodilating abilities of prostaglandins are important for the induction of experimental headache in healthy volunteers.

Pharmacological and expression profile of the prostaglandin I(2) receptor in the rat craniovascular system

Activation of the trigeminal nerve terminals around cerebral and meningeal arteries is thought to be an important patho-mechanism in migraine. Vasodilatation of the cranial arteries may also play a role in increasing nociception. Prostaglandin I(2) (PGI(2)) is capable of inducing a headache in healthy volunteers, a response that is likely to be mediated by the prostaglandin I(2) receptor (IP). This study investigates the functional and molecular characteristics of the IP receptor in the rat craniovascular system. In the closed cranial window model, iloprost, an IP receptor agonist, dilated the rat middle meningeal artery (MMA) (E(max)=170%±16%; pED(50)=6.5±0.2) but not the rat cerebral artery (CA) in vivo. The specific antagonist of the IP receptor, CAY10441, significantly blocked the iloprost-induced response dose-dependently, with the highest dose attenuating iloprost (1μgkg(-1)) induced dilatations by 70% (p<0.05). CAY10441 did not have any effect on the prostaglandin E(2)-induced vasodilatory response, thus suggesting no interaction with EP(2) and EP(4) receptors. IP receptor mRNA transcripts and protein were present in meningeal as well as in cerebral rat vasculature, and localized the IP receptor protein to the smooth vasculature of the cranial arteries (MMA, MCA and basilar artery). Together, these results demonstrate that the IP receptor mediates the dilatory effect of PGI(2) in the cranial vasculature in rats. Antagonism of this receptor might be of therapeutic relevance in acute migraine treatment.

Emerging migraine treatments and drug targets

Migraine has a 1-year prevalence of 10% and high socioeconomic costs. Despite recent drug developments, there is a huge unmet need for better pharmacotherapy. In this review we discuss promising anti-migraine strategies such as calcitonin gene-related peptide (CGRP) receptor antagonists and 5-hydroxytrypamine (5-HT)(1F) receptor agonists, which are in late-stage development. Nitric oxide antagonists are also in development. New forms of administration of sumatriptan might improve efficacy and reduce side effects. Botulinum toxin A has recently been approved for the prophylaxis of chronic migraine. Tonabersat, a cortical spreading depression inhibitor, has shown efficacy in the prophylaxis of migraine with aura. Several new drug targets such as nitric oxide synthase, the 5-HT(1D) receptor, the prostanoid receptors EP(2) and EP(4), and the pituitary adenylate cyclase receptor PAC1 await development. The greatest need is for new prophylactic drugs, and it seems likely that such compounds will be developed in the coming decade.

Lack of correlation between vasodilatation and pharmacologically induced immediate headache in healthy subjects

BACKGROUND

The causal relationship between experimental headache and vasodilatation has not been fully clarified. In the present study, we combined headache and vascular data from eight experimental studies and conducted detailed statistical analyses. Given that substances used in all these experiments were vasodilators we examined a possible correlation between headache scores and increases in arterial diameter.

METHODS

We identified nine studies and retrieved raw data in 89 healthy subjects (46 females, 43 males), mean age 27 years (range 18-59 years). The following variables were collected: maximal median headache intensity scores on a verbal rating scale (VRS) during immediate headache (0-120 minutes); the mean velocity of blood flow in the middle cerebral artery (V(meanMCA)); and the diameter of the frontal branch of the superficial temporal artery (STA) during the maximal median headache intensity.

RESULTS

The scatter plots show no relationship between maximal headache score and the relative changes in V(meanMCA) and diameter of the STA. The main analyses of covariance showed a significant effect only of heart rate on headache (p = .014). The interaction tests were insignificant for all variables.

CONCLUSIONS

The major outcome is a finding of no linear relationship between experimental immediate headache and dilatation of the MCA or STA.

Headache and cardiovascular disease: old symptoms, new proposals

Evidence of a link between headache symptoms and cardiovascular disease has rapidly grown in recent years and it is of utmost importance for the cardiologist and neurologist to be aware of this intimate connection. A brief overview of different cardiovascular diseases (namely hypertension, stroke, coronary heart disease, patent foramen ovale, atrial septal defects, atrial septal aneurisms, mitral valve prolapse, and aortic and carotid disease) that may be related to headache is presented in this article. Proposed pathophysiological mechanisms for this association and landmark studies are reviewed and discussed.

What have we learnt from triggering migraine?

PURPOSE OF REVIEW

This review presents what we have learnt from triggering migraine.

RECENT FINDINGS

Experimental studies have shown that glyceryl trinitrate (GTN), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase activating polypeptide-38 (PACAP38) and prostaglandin I2 (PGI2) induce migraine-like attacks in migraine suffers indistinguishable from their spontaneous attacks. These studies point to two key pathways to play an important role in migraine pathophysiology: cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP). At present, no valid experimental model exists to reproduce aura episodes in migraine with aura patients. Familiar hemiplegic migraine patients seem to be less sensitive to GTN and CGRP provocation compared with common types of migraine. Advances in recent imaging studies suggest neuronal mechanisms to be behind migraine attacks. The experimental headache models have resulted in development and an ongoing search of new migraine targets.

SUMMARY

Human models of migraine offer unique possibilities to study mechanisms responsible for different migraine subtypes and to explore the mechanisms of action of existing and future antimigraine drugs. Adding advanced imaging techniques to the models may lead to a better understanding of the complex events that constitutes a migraine attack and thereby more targeted ways of intervention.

Discrepancy between strong cephalic arterial dilatation and mild headache caused by prostaglandin D2 (PGD2)

Introduction: Prostaglandins (PGs) are involved in nociception and mast cell degranulation. Prostaglandin D2 (PGD2) is a vasodilatator released during mast cell degranulation. The headache-eliciting effect of PGD2 has not been studied in man.

Subjects and methods: Twelve healthy volunteers were randomly allocated to receive intravenous infusion of 384 ng/kg/min PGD2 over 25 min in a placebo-controlled, double-blind cross-over study. We recorded headache intensity and associated symptoms, velocity in the middle cerebral artery (VMCA) and diameter of the superficial temporal artery (STA) and radial artery (RA) using ultrasonography.

Results: In the period 0–14 h, 11 subjects reported headache on PGD2 compared to one subject on placebo ( P = 0.002). During the in-hospital phase (0–120 min), the area under the headache curve was larger on PGD2 compared to placebo ( P < 0.05). Median peak headache, 1 (0–1), occurred 10 min after start of PGD2 infusion. There was no difference in incidence of headache in the post-hospital phase between PGD2 ( n = 3) and placebo ( n = 1). There was a decrease in VMCA ( P < 0.001), increase in STA ( P < 0.001) and RA ( P < 0.006) diameter during PGD2 infusion compared to placebo. Peak decrease in VMCA was 28.3% after 10 min and peak increase in STA was 55.7% after 20 min on the PGD2 day. Conclusions: The present study shows that PGD2 is a very strong vasodilator of MCA, STA and RA, but causes only mild headache.

Cutaneous nociception and neurogenic inflammation evoked by PACAP38 and VIP

Pituitary adenylate cyclase-activating peptide-38 (PACAP38) and vasoactive intestinal peptide (VIP) belong to the same secretin–glucagon superfamily and are present in nerve fibers in dura and skin. Using a model of acute cutaneous pain we explored differences in pain perception and vasomotor responses between PACAP38 and VIP in 16 healthy volunteers in a double-blind, placebo-controlled, crossover study. All participants received intradermal injections of 200 pmol PACAP38, 200 pmol VIP and placebo into the volar forearm. Measurements included pain intensity on a visual analog scale (VAS), blood flow by laser Doppler flowmetry, visual flare and wheal. Pain intensities after PACAP38 and VIP were mild and limited to a short time of about 100 s after injection. The area under the VAS-time curve was larger following PACAP38 (P = 0.004) and VIP (P = 0.01) compared to placebo. We found no statistical difference in pain perception between PACAP38 and VIP. Skin blood flow increase, flare and wheal were larger after both PACAP38 (P = 0.011) and VIP (P = 0.001) compared to placebo. VIP induced a considerably larger increase in skin blood flow, flare and wheal than PACAP38 (P = 0.002). In conclusion, we found that peripheral nociceptive cutaneous responses elicited by PACAP38 and VIP are similar in healthy volunteers. This suggests that acute pain and vasomotor responses following intradermal injections of PACAP38 and VIP are primarily mediated by VPAC receptors.

Presence and vascular pharmacology of KATP channel subtypes in rat central and peripheral tissues

K(ATP) channel openers are vasodilators and induce headache in normal subjects. We previously identified the Kir6.1/SUR2B K(ATP) channel subtype in major cerebral and dural arteries of rat, pig and man. We hypothesized that craniovascular Kir6.1/SUR2B K(ATP) channels mediate the headache-inducing effects of K(ATP) channel openers and that a Kir6.1/SUR2B specific blocker might be effective in the treatment of primary headaches such as migraine. Since K(ATP) channels are ubiquitous, we characterized the K(ATP) channel subtypes in major rat cranial and peripheral arteries and organs in order to understand the possible adverse effects of a Kir6.1/SUR2B blocker. We studied the mRNA expression of K(ATP) channel subunits in rat femoral, mesenteric, renal, coronary, basilar, middle cerebral and middle meningeal arteries and in tissue from rat heart, brain, liver, colon, lung, kidney and pancreas. We also studied the effects and potencies of a panel of synthetic K(ATP) channel openers and their potential inhibition by the Kir6.1 subunit-specific K(ATP) channel blocker PNU-37883A in segments of the arteries mounted in a wire myograph. Our studies suggest that Kir6.1/SUR2B forms the major functional K(ATP) channel complex in rat cranial and peripheral arteries. The mRNA transcripts of SUR1 and Kir6.2 subunits were predominantly found in brain, pancreas and heart, while SUR2A mRNA was merely detected within the heart. K(ATP) channel blockers highly specific for the SUR2B subunit may have no adverse CNS and cardiac effects and will not affect insulin release in the pancreas. However, a SUR2B blocker may not discriminate between cranial and peripheral arteries.

Compression of superficial temporal arteries by a handmade device: a simple way to block or attenuate migraine attacks in children and adolescents

Because a prolonged compression of the major scalp arteries blocks migraine attacks in a substantial number of patients, we studied the effect of the use of a simple handmade device in blocking an incoming headache attack in children and adolescents. Thirty-seven consecutive ambulatory patients were instructed to apply, at the onset of each migraine attack, a handmade device firmly compressing both temporal arteries. Thirteen patients interrupted treatment because of intolerance of the local pain provoked by compression of the device. Of the remaining 24 patients, 17 reported benefit from using the device and 7 no effect. In these 17 patients, the percentage of attacks aborted or attenuated by early use of the device was 90.5% in the first month and 95.7% in the second month; the consumption of antipain drugs dropped from the mean 4.4 +/- 2.6 in the pre-device month to 1.3 +/- 1.6 in the first and 0.6 +/- 0.9 in the second month.

Carbachol induces headache, but not migraine-like attacks, in patients with migraine without aura

Carbachol induces headache in healthy subjects, but the migraine eliciting effect of carbachol has not previously been studied. We hypothesized that the cholinomimetic agonist carbachol would induce headache and migraine-like attacks in migraineurs. Carbachol (3 µg/kg) or placebo was randomly infused into 18 patients with migraine without aura in a double-blind crossover study. Headache was scored on a verbal rating scale from 0 to 10. Velocity in the middle cerebral artery (VMCA) and diameter of the superficial temporal artery (STA) were recorded. Fifteen patients experienced headache after carbachol compared with eight after placebo ( P = 0.039). There was no difference in incidence of migraine-like attacks after carbachol ( n = 8) compared with placebo ( n = 6) ( P = 0.687). Carbachol caused a decrease in VMCA ( P = 0.044), but no change in STA ( P = 0.089) compared with placebo. The study demonstrated that carbachol provocation is not a good model for experimental migraine.

Prostaglandin I2 (epoprostenol) triggers migraine-like attacks in migraineurs

Prostacyclin [prostaglandin I2 (PGI2)] activates and sensitizes meningeal sensory afferents. In healthy subjects PGI2 triggers headache in healthy subjects. However, the migraine-eliciting effect of PGI2 has not been systematically studied in patients with migraine. We hypothesized that intravenous infusion of the stable prostacyclin analogue epoprostenol would trigger migraine-like attacks in migraineurs. We infused 10 ng kg−1 min−1 PGI2 or placebo over 25 min in 12 migraineurs without aura in a controlled, double-blind, cross-over study and recorded headache intensity and associated symptons, velocity in the middle cerebral artery (VMCA) and diameter in the superficial temporal artery. In the period 0–14 h, 12 subjects reported headache on PGI2 day compared with three subjects on placebo day ( P = 0.004), and six subjects fulfilled the criteria for an experimentally induced migraine-like attack compared with two subjects on placebo ( P = 0.219). During infusion and post-infusion phases the AUC under the headache curve on PGI2 was significantly larger than on placebo ( P < 0.05). There was a significant VMCA decrease ( P = 0.015) and superficial temporal artery diameter increase ( P < 0.001) on PGI2 compared with placebo. In conclusion, PGI2 may trigger a migraine-like attack in migraine sufferers. We suggest sensitization of perivascular nociceptors and arterial dilation as the mode of action of PGI2-induced headache and migraine-like attacks.

Localization of COX-1 and COX-2 in the intracranial dura mater of the rat

Primary headaches such as migraine can be aborted by systemic administration of non-steroidal anti-inflammatory drugs (NSAIDs), potentially through the non-selective inhibition of cyclooxygenase (COX) activity in the intracranial meninges. In this study we have used single and double labeling immunohistochemistry to examine the distribution of the COX-1 and COX-2 isoforms in the intracranial dura mater of the rat and identify cell types that express them. COX-1 immunoreactivity was found in medium and small dural blood vessels and was co-expressed with the endothelial cell markers vimentin and the endothelial isoform of nitric oxide synthase (ecNOS). COX-1 was also found to be present in most dural mast cells. COX-2 was mainly expressed in ED2-positive resident dural macrophages. Constitutive COX-2 expression was also found in some axonal profiles, many of which were co-labeled with the nociceptor peptide marker CGRP. The findings suggest that NSAIDs may abort headache, at least in part, by inhibiting either neuronal or non-neuronal COX activity in the dura mater.

Prostaglandin E2 (PGE2) Induces Headache in Healthy Subjects

The role of prostanoids in nociception is well established. The headache-eliciting effects of prostaglandin E2 (PGE2) and its possible mechanisms have previously not been systematically studied in man. We hypothesized that infusion of PGE2 might induce headache and vasodilation of cranial vessels. PGE2 (0.40 μg kg−1 min−1) or saline was infused for 25 min into 11 healthy subjects in a cross-over, double-blind study. Headache intensity was scored on a verbal rating scale from 0 to 10. In addition, we recorded mean flow in the middle cerebral artery (VMCA) by transcranial Doppler and diameter of the superficial temporal artery (STA) by high-resolution ultrasonography. All 11 subjects reported headache on the PGE2 day and no subjects reported headache on the placebo day ( P = 0.001). During the immediate phase (0–30 min) ( P = 0.005) and the postinfusion phase (30–90 min) ( P = 0.005), the area under the curve for headache score was significantly larger on the PGE2 day compared with the placebo day. PGE2 caused dilatation of the STA (23.5%; 95% CI 14.0, 37.8) and the MCA (8.3%; 95% CI 4.0, 12.6). We suggest that PGE2 induces headache by activation and sensitization of cranial perivascular sensory afferents.

Migraine: where and how does the pain originate?

Migraine is a complex neurological disease with a genetic background. Headache is the most prominent and clinically important symptom of migraine but its origin is still enigmatic. Numerous clinical, histochemical, electrophysiological, molecular and genetical approaches form a puzzle of findings that slowly takes shape. The generation of primary headaches like migraine pain seems to be the consequence of multiple pathophysiological changes in meningeal tissues, the trigeminal ganglion, trigeminal brainstem nuclei and descending inhibitory systems, based on specific characteristics of the trigeminovascular system. This contribution reviews the current discussion of where and how the migraine pain may originate and outlines the experimental work to answer these questions.