An exploratory analysis of clinical and sociodemographic factors in CGRP-induced migraine attacks: A REFORM study.

OBJECTIVE: To investigate whether clinical and sociodemographic factors are associated with calcitonin gene-related peptide (CGRP) induced migraine attacks. METHODS: A total of 139 participants with migraine received a 20-minute intravenous infusion of CGRP (1.5 µg/min) on a single experiment day. The incidence of CGRP-induced migraine attacks was recorded using a headache diary during the 12-hour observational period post-infusion. Univariable and multivariable regression analyses were conducted to examine potential predictors' relationship with CGRP-induced migraine attacks. RESULTS: CGRP-induced migraine attacks were reported in 110 (79%) of 139 participants. Univariable analysis revealed that participants with cutaneous allodynia had higher odds of developing CGRP-induced migraine attacks, compared with those without allodynia (OR, 2.97, 95% CI, 1.28 to 7.43). The subsequent multivariable analysis confirmed this association (OR, 3.26, 95% CI, 1.32 to 8.69) and also found that participants with migraine with aura had lower odds of developing CGRP-induced migraine attacks (OR, 0.32, 95% CI, 0.12 to 0.84). CONCLUSION: Our results suggest that cutaneous allodynia and aura play a role in CGRP-induced migraine attacks, while other clinical and sociodemographic factors do not seem to have any noticeable impact. This indicates that the CGRP provocation model is robust, as the CGRP hypersensitivity remained unaffected despite differences among a heterogeneous migraine population.Trial Registration: ClinicalTrials.gov Identifier: NCT04592952.

MIA mice exhibit enteric nerve defects and are more susceptible to dextran sulfate sodium-induced colitis.

Maternal immune activation (MIA) during pregnancy impairs the development of the central nervous system as well as the peripheral nervous system. Emerging evidence indicates that individuals with MIA suffer more from gastrointestinal disorders. The present study aims to test the hypothesis that MIA-induced susceptibility to inflammatory bowel disease is due to defects in the innervation of mucosal sensory nerves. Acute dextran sulfate sodium (DSS) colitis was induced in MIA and control adult mice. Body weight loss, disease activity index and colonic histological changes were measured during colitis. The study found that MIA mice were hypersusceptible to DSS-induced colitis and that macrophage infiltration and cytokine production were elevated in the colon of MIA mice. In vitro experiments also demonstrated that colonic macrophages from MIA mice presented hyperinflammatory responses to LPS stimulation. Sensory nerve-secreted calcitonin gene-related peptide (CGRP) is an important neuropeptide in modulating enteric inflammation. Intriguingly, we found that CGRP-positive nerves were sparsely distributed in the colon of MIA mice regardless of DSS treatment. And the protein level of CGRP was significantly reduced in colon of MIA mice. However, there was no decrease in the number of CGRP-positive cell bodies in either the DRG or vagal ganglion, suggesting that innervation defects of CGRP mucosal sensory nerves exist in the colon of MIA mice. Critically, administration of recombinant CGRP to MIA mice during DSS colitis significantly reversed their hyperinflammatory pathology. Additionally, the hyperinflammatory phenotype of colonic macrophages of MIA mice could also be reversed by CGRP treatment in vitro. Collectively, these findings suggested that the sensor nerve innervation defect-induced CGRP deficiency in MIA mice participates in their increased susceptibility to colitis. Thus, sensor nerve-secreted CGRP may be a new therapeutic target for autism combined with inflammatory bowel disease.

Peripheral Nerve Denervation in Streptozotocin-Induced Diabetic Rats Is Reduced by Cilostazol.

Background and Objective: Our previous study demonstrated that consistent treatment of oral cilostazol was effective in reducing levels of painful peripheral neuropathy in streptozotocin-induced type I diabetic rats. As diabetic neuropathy is characterized by hyperglycemia-induced nerve damage in the periphery, this study aims to examine the neuropathology as well as the effects of cilostazol treatments on the integrity of peripheral small nerve fibers in type I diabetic rats. Materials and Methods: A total of ninety adult male Sprague-Dawley rats were divided into the following groups: (1) naïve (control) group; (2) diabetic rats (DM) group for 8 weeks; DM rats receiving either (3) 10 mg/kg oral cilostazol (Cilo10), (4) 30 mg/kg oral cilostazol (Cilo30), or (5) 100 mg/kg oral cilostazol (Cilo100) for 6 weeks. Pain tolerance thresholds of hind paws toward thermal and mechanical stimuli were assessed. Expressions of PGP9.5, P2X3, CGRP, and TRPV-1 targeting afferent nerve fibers in hind paw skin and glial cells in the spinal dorsal horn were examined via immunohistochemistry and immunofluorescence. Results: Oral cilostazol ameliorated the symptoms of mechanical allodynia but not thermal analgesia in DM rats. Significant reductions in PGP9.5-, P2X3-, CGRP, and TRPV-1-labeled penetrating nerve fibers in the epidermal layer indicated denervation of sensory nerves in the hind paw epidermis of DM rats. Denervation significantly improved in groups that received Cilo30 and Cilo100 in a dose-dependent manner. Cilostazol administration also suppressed microglial hyperactivation and increased astrocyte expressions in spinal dorsal horns. Conclusions: Oral cilostazol ameliorated hyperglycemia-induced peripheral small nerve fiber damage in the periphery of diabetic rats and effectively mitigated diabetic neuropathic pain via a central sensitization mechanism. Our findings present cilostazol not only as an effective option for managing symptoms of neuropathy but also for deterring the development of diabetic neuropathy in the early phase of type I diabetes.

Immunohistochemical characterization of transient receptor potential vanilloid types 2 and 1 in a trinitrobenzene sulfonic acid-induced rat colitis model with visceral hypersensitivity.

Transient receptor potential vanilloid type 2 (TRPV2) and type 1 (TRPV1) are originally identified as heat-sensitive TRP channels. We compared the expression patterns of TRPV2 and TRPV1 in the rat distal colon and extrinsic primary afferent neurons, and investigated their roles in visceral hypersensitivity in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis rats. Both TRPV2 and TRPV1 expressions in the colon, dorsal root ganglion (DRG), and nodose ganglion (NG) were significantly upregulated in the TNBS-induced colitis model. TRPV2 cell bodies co-localized with the intrinsic primary afferent marker NeuN and the inhibitory motor neuronal marker nNOS in the myenteric plexus. TRPV2 expressions were further detected in the resident macrophage marker ED2 in the mucosa. In contrast, no TRPV1-expressing cell bodies were detected in the myenteric plexus. Both TRPV2- and TRPV1-positive cell bodies in the DRG and NG were double-labeled with the neuronal retrograde tracer fluorescent fluorogold. Large- and medium-sized TRPV2-positive neurons were labeled with the A-fiber marker NF200, calcitonin gene-related peptide (CGRP), and substance P (SP) in the DRG while small-sized TRPV1-positive neurons were labeled with the C-fiber markers IB4, CGRP, and SP. TRPV2- and TRPV1-positive NG neurons were labeled with NF200 and IB4. TNBS treatment increased p-ERK1/2-positive cells in TRPV2 and TRPV1 neurons but did not affect the TRPV2 and TRPV1 subpopulations in the DRG and NG. Both TRPV2 and TRPV1 antagonists significantly alleviated visceral hypersensitivity in TNBS-induced colitis model rats. These findings suggest that intrinsic/extrinsic TRPV2- and extrinsic TRPV1-neurons contribute to visceral hypersensitivity in an experimental colitis model.

Automated detection of squint as a sensitive assay of sex-dependent calcitonin gene-related peptide and amylin-induced pain in mice.

ABSTRACT: We developed an automated squint assay using both black C57BL/6J and white CD1 mice to measure the interpalpebral fissure area between the upper and lower eyelids as an objective quantification of pain. The automated software detected a squint response to the commonly used nociceptive stimulus formalin in C57BL/6J mice. After this validation, we used the automated assay to detect a dose-dependent squint response to a migraine trigger, the neuropeptide calcitonin gene-related peptide, including a response in female mice at a dose below detection by the manual grimace scale. Finally, we found that the calcitonin gene-related peptide amylin induced squinting behavior in female mice, but not males. These data demonstrate that an automated squint assay can be used as an objective, real-time, continuous-scale measure of pain that provides higher precision and real-time analysis compared with manual grimace assessments.

Amylin Analog Pramlintide Induces Migraine-like Attacks in Patients.

OBJECTIVE: Migraine is a prevalent and disabling neurological disease. Its genesis is poorly understood, and there remains unmet clinical need. We aimed to identify mechanisms and thus novel therapeutic targets for migraine using human models of migraine and translational models in animals, with emphasis on amylin, a close relative of calcitonin gene-related peptide (CGRP). METHODS: Thirty-six migraine without aura patients were enrolled in a randomized, double-blind, 2-way, crossover, positive-controlled clinical trial study to receive infusion of an amylin analogue pramlintide or human αCGRP on 2 different experimental days. Furthermore, translational studies in cells and mouse models, and rat, mouse and human tissue samples were conducted. RESULTS: Thirty patients (88%) developed headache after pramlintide infusion, compared to 33 (97%) after CGRP (p = 0.375). Fourteen patients (41%) developed migraine-like attacks after pramlintide infusion, compared to 19 patients (56%) after CGRP (p = 0.180). The pramlintide-induced migraine-like attacks had similar clinical characteristics to those induced by CGRP. There were differences between treatments in vascular parameters. Human receptor pharmacology studies showed that an amylin receptor likely mediates these pramlintide-provoked effects, rather than the canonical CGRP receptor. Supporting this, preclinical experiments investigating symptoms associated with migraine showed that amylin treatment, like CGRP, caused cutaneous hypersensitivity and light aversion in mice. INTERPRETATION: Our findings propose amylin receptor agonism as a novel contributor to migraine pathogenesis. Greater therapeutic gains could therefore be made for migraine patients through dual amylin and CGRP receptor antagonism, rather than selectively targeting the canonical CGRP receptor. ANN NEUROL 2021;89:1157-1171.

Hypersensitivity to calcitonin gene-related peptide in chronic migraine.

OBJECTIVE: To investigate if calcitonin gene-related peptide infusion induces migraine-like attacks in chronic migraine patients. METHODS: Fifty-eight patients with chronic migraine, either with or without headache on the experimental day, were assessed for the incidence of migraine-like attacks after an intravenous infusion with calcitonin gene-related peptide 1.5 µg/min over 20 min. The primary endpoint was the incidence of migraine-like attacks after calcitonin gene-related peptide. Exploratory endpoints were the association between the incidence of migraine-like attacks and presence of headache on the experimental day, and headache frequency in the past month. Migraine-like attack data was compared to a historic cohort of 91 episodic migraine patients without headache on the experimental day. Total tenderness score, pressure-pain threshold and supra-threshold pressure pain at baseline were investigated in relation to incidence of migraine-like attacks and presence of headache on the experimental day. RESULTS: In total, 83% of the 58 chronic migraine patients developed migraine-like attacks after calcitonin gene-related peptide infusion. Migraine-like attacks were found in 92% of chronic migraine patients with headache on the experimental day compared to 65% of chronic migraine patients without headache on the experimental day (p = 0.035). No differences were observed in total tenderness score and pressure-pain threshold between chronic migraine patients with and without headache on the experimental day. The incidence of migraine-like attacks following calcitonin gene-related peptide in chronic migraine patients without headache (65%) was equal to the historic cohort of 91 episodic migraine patients without headache (67%) on the experimental day. CONCLUSIONS: Chronic migraine patients are hypersensitive to calcitonin gene-related peptide. The potency of calcitonin gene-related peptide as a migraine inductor is increased in chronic migraine patients with ongoing headache. We suggest that calcitonin gene-related peptide, besides being a migraine trigger also acts as a modulator of nociceptive transmission in the trigeminal system.

Hypersensitivity to Calcitonin Gene-Related Peptide in Post-Traumatic Headache.

OBJECTIVE: To demonstrate that calcitonin gene-related peptide (CGRP) induces headache exacerbation with migraine-like features in patients with persistent post-traumatic headache (PTH) attributed to mild traumatic brain injury (TBI). METHODS: A randomized, double-blind, placebo-controlled, two-way crossover study was conducted. Analyses were intention-to-treat. Eligible patients were aged 18 to 65 years and had a history of persistent PTH after mild TBI for at least 12 months. Patients were randomized to receive an intravenous infusion of 1.5µg/min of CGRP or placebo (isotonic saline) over 20 minutes on two separate experimental days. A 12-hour observational period was used to evaluate the following outcomes: (1) difference in incidence of headache exacerbation with migraine-like features and (2) difference in area under the curve for headache intensity scores. RESULTS: Thirty patients (mean age = 37 years, 25 women [83%]) were randomized and completed the study. During the 12-hour observational period, 21 of 30 patients (70%) developed headache exacerbation with migraine-like features after CGRP, compared with 6 patients (20%) after placebo (p < 0.001). The baseline-corrected area under the curve for headache intensity scores was significantly larger after CGRP, compared with placebo (p < 0.001). INTERPRETATION: Patients with persistent PTH are hypersensitive to CGRP, which underscores its pathophysiological importance. Furthermore, CGRP-targeted therapies might provide a novel mechanism-based treatment option for patients with persistent PTH. ANN NEUROL 2020;88:1220-1228.

Investigation of distinct molecular pathways in migraine induction using calcitonin gene-related peptide and sildenafil.

OBJECTIVE: Migraine displays clinical heterogeneity of attack features and attack triggers. The question is whether this heterogeneity is explained by distinct intracellular signaling pathways leading to attacks with distinct clinical features. One well-known migraine-inducing pathway is mediated by cyclic adenosine monophosphate and another by cyclic guanosine monophosphate. Calcitonin gene-related peptide triggers migraine via the cyclic adenosine monophosphate pathway and sildenafil via the cyclic guanosine monophosphate pathway. To date, no studies have examined whether migraine induction mediated via the cyclic adenosine monophosphate and cyclic guanosine monophosphate pathways yields similar attacks within the same patients. METHODS: Patients were subjected to migraine induction on two separate days using calcitonin gene-related peptide (1.5 µg/min for 20 minutes) and sildenafil (100 mg) in a double-blind, randomized, double-dummy, cross-over design. Data on headache intensity, characteristics and accompanying symptoms were collected until 24 hours after drug administration. RESULTS: Thirty-four patients were enrolled and 27 completed both study days. Seventeen patients developed migraine after both study drugs (63%; 95% CI: 42-81). Eight patients developed migraine on one day only (seven after sildenafil and one after calcitonin gene-related peptide). Two patients did not develop migraine on either day. Headache laterality, nausea, photophobia and phonophobia were similar between drugs in 77%, 65%, 100%, and 94%, respectively, of the 17 patients who developed attacks on both days. CONCLUSION: A majority of patients developed migraine after both calcitonin gene-related peptide and sildenafil. This supports the hypothesis that the cyclic adenosine monophosphate and cyclic guanosine monophosphate intracellular signaling pathways in migraine induction converge in a common cellular determinator, which ultimately triggers the same attacks. Trial registration: ClinicalTrials.gov Identifier: NCT03143465.

Modulatory effects of neuropeptides on pentylenetetrazol-induced epileptic seizures and neuroinflammation in rats

SUMMARY OBJECTIVE We aimed to explore the effects of neuropeptides ghrelin, obestatin, and vasoactive intestinal peptide (VIP) on seizures and plasma concentrations of neuroinflammation biomarkers including calcitonin gene-related peptide (CGRP), substance-P (SP), and interleukin-1 beta (IL-1β) in pentylenetetrazol-induced seizures in rats. METHODS Ghrelin (80 µg/kg), obestatin (1 µg/kg), VIP (25 ng/kg) or saline were administered to rats intraperitoneally 30 min before pentylenetetrazole (PTZ, 50 mg/kg) injections. Stages of epileptic seizures were evaluated by Racine's scale, and plasma CGRP, SP, and IL-1β concentrations were measured using ELISA. RESULTS Both obestatin and VIP shortened onset-time of generalized tonic-clonic seizure, respectively, moreover VIP also shortened the onset-time of first myoclonic-jerk induced by PTZ. While PTZ increased plasma CGRP, SP and IL-1β concentrations, ghrelin reduced the increases evoked by PTZ. While VIP further increased PTZ-evoked CGRP levels, it diminished IL-1β concentrations. However, obestatin did not change CGRP, SP, and IL-1β concentrations. CONCLUSION Our results suggest that ghrelin acts as an anticonvulsant, obestatin acts as a proconvulsant, and VIP has dual action on epilepsy. Receptors of those neuropeptides may be promising targets for epilepsy treatment.

RESUMO OBJETIVO Nosso objetivo foi explorar os efeitos dos neuropeptídeos grelina, obestatina e peptídeo intestinal vasoativo (VIP) nas convulsões e concentrações plasmáticas de biomarcadores neuroinflamatórios, incluindo peptídeo relacionado ao gene da calcitonina (CGRP), substância-P (SP) e interleucina-1 beta (IL-1β) em convulsões induzidas por pentilenotetrazol em ratos. MÉTODOS Grelina (80 µg/kg), obestatina (1 µg/kg), VIP (25 ng/kg) ou solução salina foram administrados a ratos intraperitonealmente 30 minutos antes de injeções de pentilenotetrazol (PTZ, 50 mg/kg). Os estágios das crises epilépticas foram avaliados pela escala de Racine e as concentrações plasmáticas de CGRP, SP e IL-1β foram medidas usando Elisa. RESULTADOS Tanto a obestatina quanto o VIP encurtaram o tempo de início da crise tônico-clônica generalizada, respectivamente. Além disso, o VIP também encurtou o tempo de início do primeiro impulso mioclônico induzido por PTZ. Enquanto o PTZ aumentou as concentrações plasmáticas de CGRP, SP e IL-1β, a grelina reduziu os aumentos evocados por PTZ. Enquanto o VIP aumenta ainda mais os níveis de CGRP evocados por PTZ, diminui as concentrações de IL-1β. No entanto, a obestatina não alterou as concentrações de CGRP, SP e IL-1β. CONCLUSÃO Nossos resultados sugerem que a grelina tem anticonvulsivante, a obestatina tem proconvulsivante e o VIP tem ação dupla na epilepsia. Receptores desses neuropeptídeos podem ser alvos promissores para o tratamento da epilepsia.

The role of genetics on migraine induction triggered by CGRP and PACAP38.

Migraine has a strong genetic component and is characterized by multiphasic events including an initial premonitory phase with premonitory symptoms (PS). Calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating peptide-38 (PACAP38) are endogenous neuropeptides that can trigger migraine attacks and have in recent years gained considerable interest in the migraine field. Yet, the exact pathophysiological mechanisms underlying CGRP- and PACAP38-induced attacks are not fully clarified. Human provocation models have shown that these peptides induce attacks in only two- thirds of migraine patients. Whether this diverse migraine response after CGRP or PACAP38 may be explained by genetic factors is unknown. The present thesis includes four studies that explore different factors that may be associated with the CGRP- and PACAP38-induced migraine response. In study I and II we investigated the role of familial predisposition (family load) and number of risk conferring gene variants on migraine attacks induced by CGRP or PA-CAP38. In study III, we investigated biochemical changes of CGRP, vasoactive intestinal peptide (VIP), S100B and TNF-alpha in the blood after PACAP38. Finally in study IV, we studied whether CGRP or PACAP38 may induce PS. Study I and II demonstrated that PACAP38 and CGRP induce migraine attacks in 63% and 72% of the patients, respectively. Moreover, we showed that patients with high family load or a high number of migraine associated gene variants did not report more migraine attacks after CGRP or PACAP38 than those with no familial predisposition or few gene variants. Study III showed that PACAP38 infusion caused changes in plasma concentrations for VIP and S100B, but not CGRP and TNF-alpha, suggesting activation of parasympathetic nerve endings. Study IV showed absence of PS after CGRP and lack of statistical difference in PS between patients who reported and not reported attacks after PACAP38 suggesting peripheral mechanisms of induction. In conclusion, the present thesis suggests that genetics factors such as family load and genetic variants do not contribute to susceptibility of migraine attacks induced by CGRP or PACAP38. Additionally, our data indicate that CGRP and PACAP38 primarily have a peripheral site of action. We believe that the acquired knowledge from this thesis on how CGRP and PACAP38 might be involved in migraine pathophysiology would contribute to the development of novel and better migraine treatments in the future.

Calcitonin gene-related peptide induced migraine attacks in patients with and without familial aggregation of migraine.

Background Calcitonin gene-related peptide provokes migraine attacks in 65% of patients with migraine without aura. Whether aggregation of migraine in first-degree relatives (family load) or a high number of risk-conferring single nucleotide polymorphisms contributes to migraine susceptibility to calcitonin gene-related peptide infusion in migraine patients is unknown. We hypothesized that genetic enrichment plays a role in triggering of migraine and, therefore, migraine without aura patients with high family load would report more migraine attacks after calcitonin gene-related peptide infusion than patients with low family load. Methods We allocated 40 previously genotyped migraine without aura patients to receive intravenous infusion of 1.5 µg/min calcitonin gene-related peptide and recorded migraine attacks including headache characteristics and associated symptoms. Information of familial aggregation was obtained by telephone interview of first-degree relatives using a validated semi-structured questionnaire. Results Calcitonin gene-related peptide infusion induced a migraine-like attack in 75% (12 out of 16) of patients with high family load compared to 52% (12 out of 23) with low family load ( P = 0.150). In addition, we found that the migraine response after calcitonin gene-related peptide was not associated with specific or a high number of risk-conferring single nucleotide polymorphisms of migraine without aura. Conclusion We found no statistical association between familial aggregation of migraine and hypersensitivity to calcitonin gene-related peptide infusion in migraine without aura patients. We also demonstrated that the currently known single nucleotide polymorphisms conferring risk of migraine without aura have no additive effect on calcitonin gene-related peptide induced migraine-like attacks.

Premonitory and nonheadache symptoms induced by CGRP and PACAP38 in patients with migraine.

Migraine attacks are often preceded by premonitory symptoms (PS) that may be triggered pharmacologically. We investigated the incidence of PS after administration of calcitonin gene-related peptide (CGRP) or pituitary adenylate cyclase-activating peptide-38 (PACAP38) in patients with migraine without aura (MO) who reported and did not report migraine-like attacks induced by these pharmacological triggers. In addition, we investigated the association between PS and familial predisposition for migraine. In our study, MO patients received continuous intravenous infusion of α-CGRP (n = 40) and PACAP38 (n = 32) for 20 minutes. Premonitory and nonheadache symptoms were recorded by a self-administered questionnaire. Information on familial predisposition was obtained by telephone interview of first-degree relatives using a validated semistructured questionnaire. Twenty-five of 40 patients (63%) developed a migraine-like attack after CGRP infusion and 23 of 32 patients (72%) developed an attack after PACAP38 infusion. Only 2 patients (9%) with a CGRP-induced migraine-like attack reported PS, whereas 11 patients (48%) reported PS after PACAP38. Patients who developed a migraine-like attack did not report more PS than did patients with no attack after CGRP (P = 0.519) or PACAP38 (P = 0.103). Additionally, we found no difference in PS between patients with familial predisposition of migraine (75%) and patients with no family predisposition (56%) (P = 0.101). In conclusion, CGRP did not induce PS, whereas PACAP38 induced PS in 48% of patients. However, CGRP and PACAP38 did not induce more PS in patients who developed an attack compared with those who did not develop an attack.

CGRP antagonist infused into the bed nucleus of the stria terminalis impairs the acquisition and expression of context but not discretely cued fear.

Calcitonin gene-related peptide (CGRP) infusions into the bed nucleus of the stria terminalis (BNST) evoke increases in startle amplitude and increases in anxiety-like behavior in the plus maze. Conversely, intra-BNST infusions of the CGRP antagonist CGRP8₋37 block unconditioned startle increases produced by fox odor. Here we evaluate the contribution of CGRP signaling in the BNST to the development and expression of learned fear. Rats received five pairings of a 3.7-sec light and footshock and were tested for fear-potentiated startle one or more days later. Neither pre-training (Experiment 1) nor pre-test (Experiment 2) infusions of the CGRP antagonist CGRP8₋37 (800 ng/BNST) disrupted fear-potentiated startle to the 3.7-sec visual cue. However, in both experiments, CGRP8₋37 infusions disrupted baseline startle increases that occurred when rats were tested in the same context as that in which they previously received footshock (Experiment 3). Intra-BNST CGRP8₋37 infusions did not disrupt shock-evoked corticosterone release (Experiment 4). These data confirm previous findings implicating BNST CGRP receptors in fear and anxiety. They extend those results by showing an important contribution to learned fear and, specifically, to fear evoked by a shock-associated context rather than a discrete cue. This pattern is consistent with previous models of BNST function that have posited a preferential role in sustained anxiety as opposed to phasic fear responses. More generally, the results add to a growing body of evidence indicating behaviorally, possibly clinically, relevant modulation of BNST function by neuroactive peptides.

Effects of glyceryl trinitrate and calcitonin gene-related peptide on BOLD signal and arterial diameter: methodological studies by fMRI and MRA.

Over the last decades MRI has proved to be very useful in the field of drug development and drug discovery. Pharmacological MRI (phMRI) explores the interaction between brain physiology, neuronal activity and drugs. The BOLD signal is an indirect method to investigate brain activity by way of measuring task related hemodynamic changes. Pharmacological substances that induce hemodynamic changes can therefore potentially alter the BOLD signal and in turn falsely can be interpreted as changes in neuronal activity. It is therefore important to characterize possible effects of a pharmacological substance on the BOLD response per se before that substance can be used in an fMRI experimental setup in order to avoid false positive or false negative results. Furthermore MRI and MRA is useful in determining the vascular site-of-action of vasoactive substances. Four substances; acetazolamide, GTN, CGRP and sumatriptan has been examined in double-blind placebo controlled crossover studies. The present thesis includes three papers with the aim to determine the site-of-action and to explore the effects of the pharmacological agents on the BOLD signal. Study I showed that acetazolamide depressed the BOLD signal by increasing CBF. GTN is known to increase CBV but had surprisingly no effect on the BOLD signal. This is probably because the GTN induces CBV increase is limited to the large arteries whereas the hemodynamic changes associated with the BOLD signal are anatomically located in the capillaries and venoules. Study II and III showed that systemic administration of CGRP induces immediate headache and dilates the MMA but contrarily to previous belief does not dilate the MCA. Nor does CGRP increase brain activity per se. Sumatriptan ameliorates headache, contracts MMA and marginally contrasts MCA without altering brain activity. In conclusion we found that acetazolamide depresses the BOLD signal while GTN does not alter the BOLD signal. While systemic administration of CGRP or sumatriptan has no direct effects on brain activity in healthy volunteers. Instead it seems that both migraine provoking peptide CGRP and anti-migraine drug sumatriptan exert their actions outside of the BBB. This thesis shows that phMRI is a powerful tool in understanding mechanisms and site-of-action of pharmacological compounds. phMRI could be a useful addition to the existing methods for development of future drugs.

Calcitonin gene-related peptide does not cause migraine attacks in patients with familial hemiplegic migraine.

BACKGROUND: Calcitonin gene-related peptide (CGRP) is a key molecule in migraine pathogenesis. Intravenous CGRP triggers migraine-like attacks in patients with migraine with aura and without aura. In contrast, patients with familial hemiplegic migraine (FHM) with known mutations did not report more migraine-like attacks compared to controls. Whether CGRP triggers migraine-like attacks in FHM patients without known mutations is unknown. OBJECTIVE: In the present study we therefore examined the migraine-inducing effect of CGRP in FHM patients without known mutations and healthy controls. METHODS AND DESIGN: Eleven patients suffering from FHM without known mutations and 11 controls received an intravenous infusion of 1.5 µg/minute CGRP over 20 minutes. The study design was a balanced and controlled provocation study. Headache and other migraine symptoms were scored for 1 hour and self-recorded hourly thereafter until 13-hour postinfusion. RESULTS: We found no difference in the incidence of migraine-like attacks between the 2 groups, with 9% (1 of 11) of patients and 0% (0 of 10) of controls reporting migraine-like headache (P = 1.00). CGRP infusion did not induce aura symptoms in any of the participants. There was no difference in the incidence of CGRP-induced delayed headaches between the groups (P = .18). CONCLUSION: In contrast to patients suffering from migraine with aura and without aura, CGRP infusion did not induce more migraine-like attacks in FHM patients without known mutations compared to controls. It seems that the majority of FHM patients with and without known mutation display no sensitivity to CGRP signaling compared to common types of migraine.

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.

Dilation by CGRP of middle meningeal artery and reversal by sumatriptan in normal volunteers.

BACKGROUND: Calcitonin gene-related peptide (CGRP) plays a fundamental role in the pathophysiology of neurovascular headaches. CGRP infusion causes headache and dilation of cranial vessels. However, it is unknown to what extent CGRP-induced vasodilation contributes to immediate head pain and whether the migraine-specific abortive drug sumatriptan, a 5-hydroxytryptamine 1B/1D agonist, inhibits CGRP-induced immediate vasodilation and headache. METHODS: We performed a double-blind, randomized, placebo-controlled, crossover study in 18 healthy volunteers. We recorded circumference changes of the middle meningeal artery (MMA) and middle cerebral artery (MCA) using magnetic resonance angiography before and after infusion (20 minutes) of 1.5 µg/min human αCGRP or placebo (isotonic saline) as well as after a 6-mg sumatriptan subcutaneous injection. RESULTS: Compared with placebo, CGRP caused significant dilation of MMA (p = 0.006) and no dilation of MCA (p = 0.69). Sumatriptan caused a marked contraction of MMA (15%-25.2%) and marginal contraction of MCA (3.9% to 5.3%). Explorative analysis revealed that sumatriptan had a more selective action on MMA compared with MCA on the CGRP day (p < 0.0001) and on the placebo day (p = 0.007). CONCLUSION: These data suggest that exogenous CGRP dilates extracranial vessels and not intracranial, and that sumatriptan exerts part of its antinociceptive action by constricting MMA and not MCA. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that IV GCRP causes dilation of the MMA but not the MCA in healthy volunteers, and that sumatriptan reverses the dilation of the MMA caused by CGRP.

Calcitonin gene-related peptide triggers migraine-like attacks in patients with migraine with aura.

INTRODUCTION: Calcitonin gene-related peptide (CGRP) is a key molecule in migraine pathogenesis. Intravenous CGRP infusion triggers delayed migraine-like attacks in patients with migraine without aura (MO). In contrast to patients with MO, in prior studies patients with familial hemiplegic migraine (FHM) did not report more migraine-like attacks compared to controls. Whether CGRP triggers migraine in patients with typical (non-hemiplegic) migraine with aura is (MA) unknown. In the present study we examined the migraine inducing effect of CGRP infusion in patients suffering from MA and healthy controls. METHODS: Fourteen patients suffering exclusively from migraine with typical aura (MA) and 11 healthy volunteers received a continuous intravenous infusion of 1.5 µg/min CGRP over 20 minutes. Headache and other migraine symptoms were scored every 10 minutes for one hour and self recorded hourly thereafter and until 13 hours post-infusion. RESULTS: CGRP infusion induced significantly more delayed headaches in MA patients (12 out of 14) than in controls (2 out of 11) (p = 0.001). Furthermore, significantly more MA patients (57%; 8 out of 14) fulfilled criteria for an experimentally induced migraine attack after CGRP than controls (0%; 0 out of 11) (P = 0.003). Four patients (28%) reported aura symptoms after CGRP infusion. CONCLUSION: CGRP triggered migraine-like attacks without aura in patients suffering exclusively from MA. It also triggered a typical aura in 28% of the patients. These data indicate similar neurobiological pathways responsible for triggering migraine headache in MA and MO patients, and suggest differences between MA/MO and FHM.

Efficacy and tolerability of MK-0974 (telcagepant), a new oral antagonist of calcitonin gene-related peptide receptor, compared with zolmitriptan for acute migraine: a randomised, placebo-controlled, parallel-treatment trial.

BACKGROUND: Calcitonin gene-related peptide (CGRP) probably has a role in migraine pathophysiology, and antagonism of its receptors might provide treatment without the vasoconstrictor effects of triptans. We aimed to assess the clinical profile of MK-0974 (telcagepant), an orally bioavailable antagonist of CGRP receptor. METHODS: In a randomised, parallel-treatment, placebo-controlled, double-blind, trial at 81 sites in the Europe and the USA, adults with migraine diagnosed by International Headache Society criteria treated moderate or severe attacks with either oral telcagepant 150 mg or 300 mg, zolmitriptan 5 mg, or placebo. The five co-primary endpoints were pain freedom, pain relief, or absence of photophobia, phonophobia, or nausea at 2 h after treatment. Analysis was by the full analysis set and multiplicity was controlled for with a step-down closed-testing procedure. This trial is registered with ClinicalTrials.gov, number NCT00442936. FINDINGS: 1380 patients were randomly assigned to receive telcagepant 150 mg (n=333) or 300 mg (354), zolmitriptan (345), or placebo (348). Telcagepant 300 mg was more effective than placebo for pain freedom (95 [27%] of 353 patients vs 33 [10%] of 343 [p<0.0001]), pain relief (194 [55%] of 353 vs 95 [28%] of 343 [p<0.0001]), and absences of phonophobia (204 [58%] of 353 vs 126 [37%] of 342 [p<0.0001]), photophobia (180 [51%] of 353 vs 99 [29%] of 342 [p<0.0001]), and nausea (229 [65%] of 352 vs 189 [55%] of 342 [p=0.0061]). Efficacy of telcagepant 300 mg and zolmitriptan 5 mg were much the same, and both were more effective than telcagepant 150 mg. Adverse events were recorded for 31% taking telcagepant 150 mg, 37% taking telcagepant 300 mg, 51% taking zolmitriptan 5 mg, and 32% taking placebo. INTERPRETATION: Telcagepant 300 mg is effective as an acute treatment for migraine with efficacy comparable to that of zolmitriptan 5 mg, but with fewer associated adverse effects. FUNDING: Merck Research Laboratories.