Platelet glycine, glutamate and aspartate in primary headache

Targeting Glutamate Neurotoxicity through Dietary Manipulation: Potential Treatment for Migraine

Glutamate, the main excitatory neurotransmitter in the central nervous system, is implicated in both the initiation of migraine as well as central sensitization, which increases the frequency of migraine attacks. Excessive levels of glutamate can lead to excitotoxicity in the nervous system which can disrupt normal neurotransmission and contribute to neuronal injury or death. Glutamate-mediated excitotoxicity also leads to neuroinflammation, oxidative stress, blood-brain barrier permeability, and cerebral vasodilation, all of which are associated with migraine pathophysiology. Experimental evidence has shown the protective effects of several nutrients against excitotoxicity. The current review focuses on the mechanisms behind glutamate's involvement in migraines as well as a discussion on how specific nutrients are able to work towards restoring glutamate homeostasis. Understanding glutamate's role in migraine is of vital importance for understanding why migraine is commonly comorbid with widespread pain conditions and for informing future research directions.

Targeting Peripheral N-Methyl-D-Aspartate Receptor (NMDAR): A Novel Strategy for the Treatment of Migraine

Backgrounds: Several acute and preventive medications were developed for the treatment of migraine. Yet, a significant proportion of patients reports an inadequate response and a lack of tolerability, emphasizing the need for new options. Glutamate is the most important excitatory neurotransmitter in the brain, and glutamate receptors including N-Methyl-D-Aspartate Receptor (NMDAR) are expressed at several levels of the trigeminovascular system, which is the anatomical and physiological substrate of migraine pain. Objective: To review preclinical and clinical studies investigating the role of the NMDAR in migraine pathophysiology. Methods: No protocol was registered for this study. References for the present review were identified from a narrative search of the PubMed database. Search terms such as glutamate, migraine, N-Methyl-D-Aspartate Receptor, and NMDAR were used. No restrictions were made in terms of the language and date of publication. Results: In animal models, administration of monosodium glutamate (MSG) activated and sensitized trigeminovascular neurons. In healthy human participants, consumption of MSG caused headaches, craniofacial sensitivity, and nausea. In in vivo models and through immunolabeling, NMDAR subunits NR1, NR2A, and NR2B were expressed in trigeminal ganglion neurons. In humans, NMDAR antagonists such as ketamine and memantine caused a significant reduction in pain intensity and monthly headache frequency. Conclusions: Accumulative evidence indicates that NMDAR is a promising new target for the treatment of migraine. Selective NMDAR antagonists without central effects are needed to investigate their therapeutic benefit in the treatment of migraine.

The NMDA receptor antagonists memantine and ketamine as anti-migraine agents

Migraine is a debilitating disorder affecting females more frequently than males. There is some evidence that drugs targeting glutamate receptors: memantine and ketamine might be beneficial in the therapy of this entity. Therefore, the purpose of this work is to present NMDA receptor antagonists, memantine and ketamine, as potential anti-migraine agents. We searched PubMed/MEDLINE, Embase, and clinical trials submitted to ClinicalTrials.gov to find publications describing eligible trials published between database inception and December 31, 2021. This comprehensive literature review summarizes data on the use of the NMDA receptor antagonists memantine and ketamine in the pharmacotherapy of migraine. Results from 20 previous and recent preclinical experiments are discussed and correlated with 19 clinical trials (including case series, open-label, and randomized placebo-controlled trials). For the purposes of this review, the authors hypothesized that the propagation of SD is a major mechanism in the pathophysiology of migraine. In several animal studies and in vitro studies, memantine and ketamine inhibited or reduced propagation of the SD. In addition, the results of clinical trials suggest that memantine or ketamine may be an effective treatment option for migraine. However, most studies on these agents lack control group. Although further clinical trials are needed, the results suggest that ketamine or memantine may be promising molecules for the treatment of severe migraine. Particular attention should be paid to people who have a treatment-resistant form of migraine with aura or have exhausted existing treatment options. For them, the drugs under discussion could represent an interesting alternative in the future.

Exploring Novel Therapeutic Targets in the Common Pathogenic Factors in Migraine and Neuropathic Pain

Migraine and neuropathic pain (NP) are both painful, disabling, chronic conditions which exhibit some symptom similarities and are thus considered to share a common etiology. The calcitonin gene-related peptide (CGRP) has gained credit as a target for migraine management; nevertheless, the efficacy and the applicability of CGRP modifiers warrant the search for more effective therapeutic targets for pain management. This scoping review focuses on human studies of common pathogenic factors in migraine and NP, with reference to available preclinical evidence to explore potential novel therapeutic targets. CGRP inhibitors and monoclonal antibodies alleviate inflammation in the meninges; targeting transient receptor potential (TRP) ion channels may help prevent the release of nociceptive substances, and modifying the endocannabinoid system may open a path toward discovery of novel analgesics. There may exist a potential target in the tryptophan-kynurenine (KYN) metabolic system, which is closely linked to glutamate-induced hyperexcitability; alleviating neuroinflammation may complement a pain-relieving armamentarium, and modifying microglial excitation, which is observed in both conditions, may be a possible approach. Those are several potential analgesic targets which deserve to be explored in search of novel analgesics; however, much evidence remains missing. This review highlights the need for more studies on CGRP modifiers for subtypes, the discovery of TRP and endocannabinoid modulators, knowledge of the status of KYN metabolites, the consensus on cytokines and sampling, and biomarkers for microglial function, in search of innovative pain management methods for migraine and NP.

Migraine headache pathophysiology

In both episodic and chronic migraine, headache is the most disabling symptom that requires medical care. The migraine headache is the most well-studied symptom of migraine pathophysiology. The trigeminal system and the central processing of sensory information transmitted by the trigeminal system are of considerable importance in the pathophysiology of migraine headache. Glutamate is the main neurotransmitter that drives activation of the ascending trigeminal and trigeminothalamic pathways. The neuropeptide, calcitonin gene-related peptide (CGRP) that is released by the trigeminal system, plays a crucial role in the neurobiology of headache. Peripheral and central sensitizations associated with trigeminal sensory processing are neurobiologic states that contribute to both the development of headache during a migraine attack and the maintenance of chronic migraine.

Are Migraine With and Without Aura Really Different Entities?

Background: Migraine research is booming with the rapidly developing neuroimaging tools. Structural and functional alterations of the migrainous brain were detected with MRI. The outcome of a research study largely depends on the working hypothesis, on the chosen measurement approach and also on the subject selection. Against all evidence from the literature that migraine subtypes are different, most of the studies handle migraine with and without aura as one disease. Methods: Publications from PubMed database were searched for terms of "migraine with aura," "migraine without aura," "interictal," "MRI," "diffusion weighted MRI," "functional MRI," "compared to," "atrophy" alone and in combination. Conclusion: Only a few imaging studies compared the two subforms of the disease, migraine with aura, and without aura, directly. Functional imaging investigations largely agree that there is an increased activity/activation of the brain in migraine with aura as compared to migraine without aura. We propose that this might be the signature of cortical hyperexcitability. However, structural investigations are not equivocal. We propose that variable contribution of parallel, competing mechanisms of maladaptive plasticity and neurodegeneration might be the reason behind the variable results.

Intracortical facilitation within the migraine motor cortex depends on the stimulation intensity. A paired-pulse TMS study

Introduction

Connectivity within the primary motor cortex can be measured using the paired-pulse transcranial magnetic stimulation (TMS) paradigm. This evaluates the effect of a first conditioning stimulus on the motor evoked potential (MEP) elicited by a second test stimulus when different interstimulus intervals are used. Aim of the present study was to provide, in patients suffering from migraine without aura (MwoA), additional information on intracortical facilitation (ICF), short intracortical inhibition (SICI), and long intracortical inhibition (LICI), using different intensities of the test stimulus (TS).

Methods

We enrolled 24 patients with episodic MwoA and 24 age- and sex-matched healthy volunteers. Both patients and controls were randomly assigned to two different experimental groups: the first group underwent evaluation of ICF, while in the second group we assessed SICI and LICI. All these measures were assessed by using three different suprathreshold intensities of the TS (110%, 130% and 150% of the resting motor threshold, RMT). Interstimulus intervals (ISIs) of 10 ms were used for testing ICF, while SICI and LICI were carried out by using 2 ms and 100 ms ISIs respectively. All migraine patients underwent the experimental protocol while in the interictal pain-free state.

Results

A main finding of the study was that an increased ICF could be seen in migraineurs as compared to the healthy subjects only by using a 110% intensity of the TS. Instead, no significant differences were observed between patients and controls as regards both measures of intracortical inhibition.

Conclusion

We show that hyperresponsivity of the glutamatergic intracortical circuits can be detected in the migraine motor cortex only by applying a low suprathreshold intensity of stimulation. Our results strengthen the notion that, to be reliable, the assessment of cortical excitability in migraine should always include evaluation of the cortical response to different stimulation intensities.

Metabolic assessment of a migraine model using relaxation-enhanced 1 H spectroscopy at ultrahigh field

PURPOSE

This study evaluates biochemical imbalances in a rat model that reflects dysfunctional pathways in migraine. The high sensitivity and spectral dispersion available to 1 H MRS at 21.1 T expands metabolic profiling in this migraine model to include lactate (Lac), taurine (Tau), aspartate, and Gly-a mixture of glycine, glutamine, and glutamate.

METHODS

Sprague-Dawley male rats were administered in situ an intraperitoneal injection of nitroglycerin (NTG) to induce the migraine analogue or saline as a control. A selective relaxation-enhanced MR spectroscopy sequence was used to target upfield metabolites from a 4-mm3 voxel for 2.5 h after injection.

RESULTS

Significant increases were evident for Lac as early as 10 min after NTG injection, peaking over 50% compared with baseline and control (normalized Lac/N-acetyl aspartate with NTG = 1.54 ± 0.65 versus with saline = 0.99 ± 0.08). Tau decreased progressively in controls over 2 h after injection, but remained elevated with NTG, peaking at 105 min after injection (normalized Tau/N-acetyl aspartate with NTG = 1.10 ± 0.18 versus with saline = 0.85 ± 0.14). Total creatine under NTG showed significant decreases with time and compared with saline; Gly demonstrated temporal increases for NTG.

CONCLUSIONS

These changes indicate an altered metabolic profile in the migraine analogue consistent with early changes in neural activity and/or vasodilation consistent with progressively enhanced neuroprotection and osmoregulation. Magn Reson Med 79:1266-1275, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Interactions between the Kynurenine and the Endocannabinoid System with Special Emphasis on Migraine

Both the kynurenine and the endocannabinoid systems are involved in several neurological disorders, such as migraine and there are increasing number of reports demonstrating that there are interactions of two systems. Although their cooperation has not yet been implicated in migraine, there are reports suggesting this possibility. Additionally, the individual role of the endocannabinoid and kynurenine system in migraine is reviewed here first, focusing on endocannabinoids, kynurenine metabolites, in particular kynurenic acid. Finally, the function of NMDA and cannabinoid receptors in the trigeminal system-which has a crucial role in the pathomechanisms of migraine-will also be discussed. The interaction of the endocannabinoid and kynurenine system has been demonstrated to be therapeutically relevant in a number of pathological conditions, such as cannabis addiction, psychosis, schizophrenia and epilepsy. Accordingly, the cross-talk of these two systems may imply potential mechanisms related to migraine, and may offer new approaches to manage the treatment of this neurological disorder.

Platelet Glutamate Uptake and Release in Migraine With and Without Aura

Glutamate may play an important role in the pathogenesis of migraine: glutamate release in the brain may be involved in the development of spreading depression and increased concentrations of this amino acid have been reported in plasma and platelets from migraine patients. Here we assessed platelet glutamate uptake and release in 25 patients affected by migraine with aura (MA) and 25 patients affected by migraine without aura (MoA), comparing the results with a group of 20 healthy matched controls. Both glutamate release from stimulated platelets and plasma concentrations of the amino acid were assessed by high-performance liquid chromatography, and were increased in both types of migraine, although more markedly in MA. Platelet glutamate uptake, assessed as 3H-glutamate intake, was increased in MA, while it was reduced in MoA with respect to the control group. These results support the view that MA might involve different pathophysiological mechanisms from MoA and, specifically, up-regulation of the glutamatergic metabolism. Understanding these dysfunctional pathways could lead to new, possibly more successful therapeutic approaches to the management of migraine.

Effects of a honeybee sting on the serum free amino acid profile in humans

The aim of this study was to assess the response to a honeybee venom by analyzing serum levels of 34 free amino acids. Another goal of this study was to apply complex analytic-bioinformatic-clinical strategy based on up-to-date achievements of mass spectrometry in metabolomic profiling. The amino acid profiles were determined using hybrid triple quadrupole/linear ion trap mass spectrometer coupled with a liquid chromatography instrument. Serum samples were collected from 27 beekeepers within 3 hours after they were stung and after a minimum of 6 weeks following the last sting. The differences in amino acid profiles were evaluated using MetaboAnalyst and ROCCET web portals. Chemometric tests showed statistically significant differences in the levels of L-glutamine (Gln), L-glutamic acid (Glu), L-methionine (Met) and 3-methyl-L-histidine (3MHis) between the two analyzed groups of serum samples. Gln and Glu appeared to be the most important metabolites for distinguishing the beekeepers tested shortly after a bee sting from those tested at least 6 weeks later. The role of some amino acids in the response of an organism to the honeybee sting was also discussed. This study indicated that proposed methodology may allow to identify the individuals just after the sting and those who were stung at least 6 weeks earlier. The results we obtained will contribute to better understanding of the human body response to the honeybee sting.

Activation of 5-hydroxytryptamine1B/1D/1F receptors as a mechanism of action of antimigraine drugs

INTRODUCTION

The introduction of the triptans (5-hydroxytryptamine (5-HT)1B/1D receptor agonists) was a great improvement in the acute treatment of migraine. However, shortcomings of the triptans have prompted research on novel serotonergic targets for the treatment of migraine.

AREAS COVERED

In this review the different types of antimigraine drugs acting at 5-HT receptors, their discovery and development are discussed. The first specific antimigraine drugs were the ergot alkaloids, consisting of ergotamine, dihydroergotamine and methysergide, which are agonists at 5-HT receptors, but can also bind α-adrenoceptors and dopamine receptors. In the 1990s, the triptans became available on the market. They are 5-HT1B/1D receptor agonists, showing fewer side effects due to their receptor specificity. In the last years, compounds that bind specifically to 5-HT1D, 5-HT1F and 5-HT7 receptors have been explored for their antimigraine potential. Furthermore, the serotonergic system seems to act in tight connection with the glutamatergic as well as the CGRP-ergic systems, which may open novel therapeutic avenues.

EXPERT OPINION

Although the triptans are very effective in treating migraine attacks, their shortcomings have stimulated the search for novel drugs. Currently, the focus is on 5-HT1F receptor agonists, which seem devoid of vascular side effects. Moreover, novel compounds that affect multiple transmitter and/or neuropeptide systems that are involved in migraine could be of therapeutic relevance.

Glutamate oxaloacetate transaminase: a new key in the dysregulation of glutamate in migraine patients

OBJECTIVE

Based on the capacity of the blood-resident enzyme glutamate oxaloacetate transaminase (GOT) to metabolize blood glutamate, our aim was to study the association of GOT activity with serum glutamate levels and clinical parameters in patients with migraine.

METHODS

This case-control study included 45 episodic migraine patients (IHS 2004 criteria) and 16 control subjects. We analyzed glutamate and GOT activity in peripheral blood samples obtained during interictal periods and migraine attacks ( N  = 15). Frequency, severity, and duration of attacks and time of evolution were also recorded.

RESULTS

Migraine patients showed lower GOT activity than controls (15.2 ± 2.9 vs. 18.7 ± 3.8 U/l) and higher levels of glutamate (153.7 ± 68.6 vs. 121.5 ± 59.2 μM) (all P  < 0.05). A negative correlation was found between GOT activity and glutamate levels ( R  = -0.493; P  < 0.0001) in interictal periods; however, this negative correlation was lost during attacks ( R  = -0.026; P  = 0.925). During attacks, we found a positive correlation between the time elapsed from attack onset and glutamate levels ( R  = 0.738; P  < 0.0001), but not for GOT activity ( R  = -0.075; P  = 0.809).

CONCLUSIONS

Migraine patients showed reduced GOT activity and increased levels of blood glutamate levels as compared to control subjects. Furthermore, a negative correlation was found between GOT activity and glutamate levels in interictal periods.

Pathogenesis of migraine: role of neuromodulators

The pathogenesis of migraine is still, today, a hotly debated issue. Recent biochemical studies report the occurrence in migraine of metabolic abnormalities in the synthesis of neurotransmitters and neuromodulators. These include a metabolic shift directing tyrosine metabolism toward the decarboxylation pathway, therein resulting in an unphysiological production of noradrenaline and dopamine along with increased synthesis of traces amines such as tyramine, octopamine, and synephrine. This biochemical alteration is possibly favored by impaired mitochondrial function and high levels of glutamate in the central nervous system (CNS) of migraine patients. The unbalanced levels of the neurotransmitters (dopamine and noradrenaline) and neuromodulators (eg, tyramine, octopamine, and synephrine) in the synaptic dopaminergic and noradrenergic clefts of the pain matrix pathways may activate, downstream, the trigeminal system that releases calcitonin gene-related peptide. This induces the formation of an inflammatory soup, the sensitization of first trigeminal neuron, and the migraine attack. In view of this, we propose that migraine attacks derive from a top-down dysfunctional process that initiates in the frontal lobe in a hyperexcitable and hypoenergetic brain, thereafter progressing downstream resulting in abnormally activated nuclei of the pain matrix.

Delayed development of visual motion processing in childhood migraine

Introduction: Altered visual processing has been observed in adult migraineurs. But because visual processing has not been studied in paediatric cases, it is not known whether such visual system alterations are already present in early development. We therefore used a dynamic visual task to investigate motion detection threshold in paediatric migraine.

Methods: Fourteen migraineurs and 21 controls participated in the study (age range: 8–17 years). The minimal percentage of coherently moving dot stimuli at which subjects were still able to detect coherent movement (absolute threshold) was determined using a random dot kinematogram paradigm.

Results: Motion coherence detection threshold was higher in migraineurs ( p < 0.05). This difference between groups was more pronounced at younger ages, but migraineurs seem to catch up with healthy controls over the years.

Conclusions: Children with migraine exhibit a delayed development of visual motion processing. This might be a useful supplementary biomarker in paediatric migraine.

White matter microstructural alterations in migraine: a diffusion-weighted MRI study

Migraine is a common and disabling neurological disease. The pathomechanism that underlies the disorder is not entirely understood, and reliable biomarkers are missing. In the current analysis we looked for microstructural alterations of the brain white matter in migraine patients by means of diffusion-weighted magnetic resonance imaging. The measurements were carried out with a novel approach based on fine-tuned nonlinear registration and nonparametric permutation test in an alignment-invariant tract representation (Tract-Based Spatial Statistics). We found reduced fractional anisotropy in the right frontal white matter cluster of migraine patients. In the same region we also found increased mean diffusivity and increased radial diffusivity. The probabilistic tractography showed connection of this cluster to other parts of the pain network (orbitofrontal cortex, insula, thalamus, dorsal midbrain). We speculate that these findings reflect maladaptive plastic changes or white matter disintegration.

Migraine with aura: conventional and non-conventional treatments

Migraine with aura (MwA) is a primary headache that affects up 30% of migraine patients. Although the frequency of MwA attacks is usually low and the majority of migraine sufferers do not need prophylactic treatment(s), same particular patients do. This occurs when the neurological symptoms, that characterize the auras, determine anxiety to the migraine sufferers and when the frequency of MwA attacks is or becomes high. In this study, we review the few therapeutic conventional options specifically devoted to cure MwA attacks present in the literature together with those, recent, non-conventional.

The lack of peripheral pathology in migraine headache

This article reviews the baffling problem of the pathophysiology behind a peripheral genesis of migraine pain--or more particularly the baffling problem of its absence. I examine a number of pathophysiological states and the effector mechanisms for these states and find most of them very plausible and that they are all supported by abundant evidence. However, this evidence is mostly indirect; to date the occurrence of any of the presumed pathological states has not been convincingly demonstrated. Furthermore, there is little evidence of increased trigeminal sensory traffic into the central nervous system during a migraine attack. The article also examines a number of observations and experimental programs used to bolster a theory of peripheral pathology and suggests reasons why they may in fact not bolster it. I suggest that a pathology, if one exists, may be in the brain and even that it may not be a pathology at all. Migraine headache might just happen because of random noise in an exquisitely sensitive and complex network. The article suggests an experimental program to resolve these issues.

Activation of central trigeminovascular neurons by cortical spreading depression

OBJECTIVE

Cortical spreading depression (CSD) has long been implicated in migraine attacks that begin with visual aura. Having shown that a wave of CSD can trigger long-lasting activation of meningeal nociceptors--the first-order neurons of the trigeminovascular pathway thought to underlie migraine headache--we now report that CSD can activate central trigeminovascular neurons in the spinal trigeminal nucleus (C1-2).

METHODS

Stimulation of the cortex with pinprick or KCl granule was used to induce CSD in anesthetized rats. Neuronal activity was monitored in C1-2 using single-unit recording.

RESULTS

In 25 trigeminovascular neurons activated by CSD, mean firing rate (spikes/s) increased from 3.6 ± 1.2 before CSD (baseline) to 6.1 ± 1.8 after CSD (p < 0.0001) for a period >13 minutes. Neuronal activity returned to baseline level after 30.0 ± 3.1 minutes in 14 units, and remained elevated for 66.0 ± 8.3 (22-108) minutes through the entire recording period in the other 11 units. Neuronal activation began within 0.9 ± 0.4 (0-2.5) minutes after CSD in 7 neurons located in laminae I-II, or after a latency of 25.1 ± 4.0 (7-75) minutes in 9 neurons located in laminae I-II, and 9 neurons located in laminae III-V. In 27 trigeminovascular neurons not activated by CSD, mean firing rate was 2.0 ± 0.7 at baseline and 1.8 ± 0.7 after CSD.

INTERPRETATION

We propose that CSD constitutes a nociceptive stimulus capable of activating peripheral and central trigeminovascular neurons that underlie the headache of migraine with aura.

14th International Headache Congress: clinical highlights

The 14th International Headache Congress was held in Philadelphia in September 2009. During the Congress, many important basic, translational, and patient-oriented research studies were presented. In this and an accompanying manuscript, the work that has been deemed to be among the most innovative and significant is summarized. This manuscript discusses the best clinical research, while the accompanying manuscript summarizes the top basic science research. Here, we provide background and summarize Congress presentations on novel agents for migraine treatment, botulinum toxin therapy for chronic migraine, new methods for administration of headache medications, and nerve stimulation for the treatment of medically refractory headaches.

Pathogenesis of migraine: from neurotransmitters to neuromodulators and beyond

Here, in this review, we present our hypothesis of the migraine pathogenesis. We believe that migraine attacks derive from a top-down dysfunctional process that initiates in a hyperexcitable and hypoenergetic brain in the frontal lobe and downstream in abnormally activated nuclei of the pain matrix. This hypothesis derived from the results of the biochemical studies, mainly generated from our laboratory, on the possible metabolic shifts of tyrosine toward an activation of decarboxylase enzyme activity with an increased synthesis of traces amines, i.e. tyr, oct and syn, and an unphysiological synthesis of noradrenalin and dopamine. This metabolic shift is possibly favored by the reduced mitochondrial energy and high levels of glutamate in CNS of migraine patients. The unbalanced levels of neurotransmitters (DA and NE) and neuromodulators (tyr, oct and syn) in the synaptic dopaminergic and noradrenergic clefts of the pain matrix may activate, downstream, the trigeminal system that releases calcitonin gene-related G peptide. This induces the formation of an inflammatory soup, the sensitization of first trigeminal neuron and the migraine attack.

Activation of meningeal nociceptors by cortical spreading depression: implications for migraine with aura

Attacks of migraine with aura represent a phenomenon in which abnormal neuronal activity in the cortex produces sensory disturbances (aura) some 20-40 min before the onset of headache. The purpose of this study was to determine whether cortical spreading depression (CSD)--an event believed to underlie visual aura--can give rise to activation of nociceptors that innervate the meninges--an event believed to set off migraine headache. CSD was induced in anesthetized male rats by stimulation of the visual cortex with electrical pulses, pin prick, or KCl; single-unit activity of meningeal nociceptors was monitored in vivo in the rat before and after CSD. Regardless of the method of cortical stimulation, induction of CSD was recorded in 64 trials. In 31 of those trials, CSD induced a twofold increase in meningeal nociceptor firing rate that persisted for 37.0 +/- 4.6 min in trials in which activity returned to baseline, or >68 min in trials in which activity remained heightened at the time recording was interrupted. In two-thirds of the trials, onset of long-lasting neuronal activation began approximately 14 min after the wave of CSD. The findings demonstrates for the first time that induction of CSD by focal stimulation of the rat visual cortex can lead to long-lasting activation of nociceptors that innervate the meninges. We suggest that migraine with aura is initiated by waves of CSD that lead up to delayed activation of the trigeminovascular pathway.

Excitatory neurotransmitters in brain regions in interictal migraine patients

OBJECTIVE

To examine biochemical differences in the anterior cingulate cortex (ACC) and insula during the interictal phase of migraine patients. We hypothesized that there may be differences in levels of excitatory amino acid neurotransmitters and/or their derivatives in migraine group based on their increased sensitivity to pain.

METHODS

2D J-resolved proton magnetic resonance spectroscopy (1H-MRS) data were acquired at 4.0 Tesla (T) from the ACC and insula in 10 migraine patients (7 women, 3 men, age 43 +/- 11 years) and 8 age gender matched controls (7 women, 3 men, age 41 +/- 9 years).

RESULTS

Standard statistical analyses including analysis of variance (ANOVA) showed no significant metabolite differences between the two subject cohorts in the ACC nor the insula. However, linear discriminant analysis (LDA) introduced a clear separation between subject cohorts based on N-acetyl aspartylglutamate (NAAG) and glutamine (Gln) in the ACC and insula.

CONCLUSION

These results are consistent with glutamatergic abnormalities in the ACC and insula in migraine patients during their interictal period compared to healthy controls. An alteration in excitatory amino acid neurotransmitters and their derivatives may be a contributing factor for migraineurs for a decrease in sensitivity for migraine or a consequence of the chronic migraine state. Such findings, if extrapolated to other regions of the brain would offer new opportunities to modulate central system as interictal or preemptive medications in these patients.

Effective prophylactic treatments of migraine lower plasma glutamate levels

The role of glutamate in migraine treatment has not been much studied, even if this amino acid seems to be crucial in the pathogenesis of migraine. Our aim was to determine if there were differences in the plasma levels of glutamate between migraine patients and control subjects and if plasma levels of glutamate in migraine patients modified after 8 weeks of prophylactic treatment. We studied 24 patients with diagnosis of migraine without aura according to International Classification of Headache Disorders, 2nd edn criteria, and 24 age- and sex-matched healthy subjects, as controls. In migraineurs the level of glutamate was measured before and after 8 weeks of prophylactic treatment (topiramate 50 mg/day, five patients; amitriptyline 20 mg/day, seven patients; flunarizine 5 mg/day, seven patients; propranolol 80 mg/day, five patients). Venous blood samples were taken in the morning, after overnight fasting, and at least 3 days after the last migraine day. Glutamate levels were measured by means of a fluorimetric detector high-pressure liquid chromatographic method. Plasma levels of glutamate were significantly higher in migraine patients-either before (61.79 +/- 18.75 micromol/l) or after prophylactic treatment (17.64 +/- 5.08 micromol/l)-than in controls (9.36 +/- 2.1 micromol/l) (P < 0.05, anova followed by Newman-Keuls' test). After prophylactic treatment, with headache frequency reduced, plasma glutamate levels were significantly lower in the same patient with respect to the prior baseline level (P < 0.0001, Student's t-test for paired data), without any differences depending on the kind of prophylactic drug. Effective prophylactic treatments reducing high glutamate plasma levels found in migraine patients could act on the underlying mechanism that contributes to cause migraine. Plasma glutamate level monitoring in migraine patients might serve as a biomarker of response to treatments and as an objective measure of disease status.

Glutamate Levels in Cerebrospinal Fluid and Triptans Overuse in Chronic Migraine

OBJECTIVE

Chronic migraine (CM) is a common disorder, affecting 2% to 3% of the general population. Glutamate is implicated in cortical spreading depression, trigeminovascular activation, central sensitization, and may be linked to migraine chronification. Triptans brought a novel option for the acute migraine treatment. As the development of central sensitization impacts upon the effectiveness of triptan therapy, we hypothesized that glutamate might be related to triptan response mechanisms.

METHODS

We studied 19 patients diagnosed with CM according to the International Headache Society (2004) criteria. Patients were divided in those overusing analgesics (NSAIDs); those without overuse, and those overusing triptans.

RESULTS

Cerebrospinal fluid (CSF) glutamate levels were similar in patients overusing acute medications (0.335 +/- 0.225 micromol) compared to those without overuse (0.354 +/- 0.141 micromol), P= NS). In contrast, patients overusing triptans had CSF glutamate levels significantly lower than that observed in nonoverusers (0.175 +/- 0.057 vs 0.354 +/- 0.141 micromol, P= 0.015), and significantly higher than controls (0.175 +/- 0.057 vs 0.109 +/- 0.066 micromol, P= 0.039). In triptan overusers, CSF glutamate levels, although lower, were not significantly different from patients overusing other types of analgesics.

CONCLUSIONS

Our study showed lower glutamate levels in CSF of CM patients overusing triptans. Glutamate may be implicated in triptan response mechanisms, triptans may work in part by reducing extracellular glutamate levels in the brain.

Free amino acid and dipeptide changes in the body fluids from Alzheimer's disease subjects

Our aim was to determine changes in free amino acid (FAA) and dipeptide (DP) concentrations in probable Alzheimer's disease (pAD) subjects compared with control (CT) subjects using liquid chromatography and electrospray ionization tandem mass spectrometry (LCMS2). We recruited gender- and age-matched study participants based on neurological and neuropsychological assessments. We measured FAAs and DPs in cerebrospinal fluid (CSF), plasma and urine using LCMS2 with selected reaction monitoring (SRM). Imidazole-containing FAAs (histidine, methyl-histidine), catecholamines (L-DOPA and dopamine), citrulline, ornithine, glycine and antioxidant DPs (carnosine and anserine) accounted for the major changes between CT and pAD. Carnosine levels were significantly lower in pAD (328.4 +/- 91.31 nmol/dl) than in CT plasma (654.23 +/- 100.61 nmol/dl). In contrast, L-DOPA levels were higher in pAD (1400.84 +/- 253.68) than CT (513.10 +/- 121.61 nmol/dl) plasma. These data underscore the importance of FAA and DP metabolism in the pathogenesis of AD. Since our data show changes in antioxidants, neurotransmitters and their precursors, or FAA associated with urea metabolism in pAD compared with CT, we propose that manipulation of these metabolic pathways may be important in preventing AD progression.

Correlation between plasma levels of glutamate, alanine and serine with severity of depression

The goal of this study was to evaluate the utility of using plasma levels of amino acids as an indicator of the severity of depression. The samples were collected from 23 depressed patients receiving antidepressant medication, and were compared to 31 healthy subjects. The plasma levels of amino acids were determined using HPLC with fluorometric detection. The severity of depression was evaluated using the Hamilton Depression Rating Scale (HAM-D) scores. Plasma levels of glutamate, glutamine, glycine and taurine were significantly increased in the depressed patients compared to the controls. Statistical analysis indicated a positive correlation between glutamate and alanine levels and HAM-D scores and a negative correlation of L-serine with HAM-D scores. The results indicate that plasma level of glutamate, alanine and L-serine could reflect the severity of depression rather than glutamine, glycine and taurine.

Human platelets express the synaptic markers VGLUT1 and 2 and release glutamate following aggregation

Vesicular glutamate transporters (VGLUTs) are involved in storing glutamate for secretion at the level of glutamatergic axon terminals, and for this reason they have been extensively used as markers to identify glutamate-releasing cells. Platelets have been considered as a suitable model for studying glutamatergic dysfunction because they perform glutamate uptake and express both external transporters, and NMDA-like receptors. Here, we show that platelets express the pre-synaptic markers VGLUT1 and VGLUT2 and release glutamate following aggregation, implying a possible contributory role in the pathophysiology of stroke, migraine, and other excitotoxic disorders.

Indomethacin, alone and combined with prochlorperazine and caffeine, but not sumatriptan, abolishes peripheral and central sensitization in in vivo models of migraine

Recently it has been proposed that the throbbing pain of migraine is mediated by sensitization of peripheral trigeminovascular neurons, and that cutaneous allodynia of migraine is mediated by sensitization of central trigeminovascular neurons, and, moreover, that the triptans are less effective in aborting a migraine attack if the central sensitization is already established. The combination of indomethacin, prochlorperazine, and caffeine (IndoProCaf) is a drug of well-established use in the acute treatment of migraine. The aim of this study was to investigate whether the 3 active principles of IndoProCaf, alone and combined, compared to sumatriptan, were able to abolish the peripheral sensitization induced by kainic acid and the central sensitization induced by N-methyl-D-aspartate (NMDA) in in vivo models of hyperalgesia. The study showed that indomethacin or IndoProCaf is able to abolish both the kainic acid-induced and the NMDA-induced hyperalgesia. If administered at different times, IndoProCaf was always effective in reversing the kainic acid-induced hyperalgesia. Sumatriptan was not able to reverse either the kainic acid-induced or the NMDA-induced hyperalgesia. The efficacy of indomethacin, alone and combined with prochlorperazine and caffeine, in abolishing peripheral and central sensitization in in vivo models of hyperalgesia is a further explanation of the clinical efficacy of IndoProCaf in the treatment of migraine.

PERSPECTIVE

This study suggests that, although triptans were shown to be able to abort migraine attacks only if given before the establishment of cutaneous allodynia and central sensitization, IndoProCaf should be able to abort migraine attacks independently from the time of administration, because it is able to abolish an already established peripheral and central sensitization.

Cerebrospinal fluid glutamate levels in chronic migraine

Both preclinical and clinical data link glutamate to the migraine pathophisiology. Altered plasma, platelets and cerebrospinal (CSF) glutamate levels have been reported in migraine patients. Chronic migraine is comorbid with several conditions. It has been recently shown chronic migraine comorbidity with fibromyalgia. The objective of this study was to study cerebrospinal fluid glutamate levels in chronic migraine patients with and without fibromyalgia. We studied 20 chronic migraine patients, with and without fibromyalgia, compared to age-sex matched controls. CSF glutamate levels were measured by HPLC. CSF glutamate demonstrated significantly higher levels in patients with fibromyalgia compared to those without fibromyalgia. Patients overall had higher CSF glutamate levels than controls. Mean pain score correlated with glutamate levels in chronic migraine patients. Tender points, the hallmark of fibromyalgia, can be considered as pressure allodynia, and is probably mediated by central sensitization, with increase in CSF glutamate levels. We postulate chronic migraine patients with fibromyalgia, in addition to have more disabling headaches, suffer from a more severe central sensitization process. This subtype of patients may respond to medications modulating glutamate receptors. Headache intensity correlate with glutamate levels in chronic migraine patients.

Role of Magnesium, Coenzyme Q10, Riboflavin, and Vitamin B12 in Migraine Prophylaxis

Migraine is a neurovascular syndrome characterized by recurrent headache associated with other symptoms, eventually preceded by aura. This chapter reviews the involvement of some mineral, coenzyme, and vitamin defects in the pathogenesis of migraine headaches and focuses on their potential therapeutic use in the preventive treatment for migraine. The therapeutic potential of magnesium, coenzyme Q(10), riboflavin, and vitamin B(12) can be cautiously inferred from some published open clinical trials; it should, however, be considered that double-blind randomized larger studies are needed to correctly estimate the impact of the placebo effect in these promising therapies.

The link between glutamate and migraine

Migraine pain-relay centers, including the trigeminal ganglion, trigeminal nucleus caudalis, and thalamus, contain glutamate-positive neurons, and glutamate activates the trigeminal nucleus caudalis. Glutamate is implicated in cortical spreading depression, trigeminovascular activation, and central sensitization. Glutamate receptor-subtype antagonists are effective in preclinical models of migraine, and in the clinic. These preclinical and clinical observations argue for a strong link between migraine and the glutamatergic system, a link that is important to further characterize in an effort to better understand migraine mechanisms and deliver effective therapies.

The electrophysiology of migraine

Migraine is currently regarded as a neurovascular disorder of trigeminal sensory processing, generated centrally, probably at the level of the brainstem. In the past, electrophysiological techniques have drawn no definite conclusions on either interictal or ictal changes in migraineurs compared with controls, largely because of methodological differences. Recently, two findings have been shown consistently: an interictal increasing lack of habituation of evoked potentials with a normalization at the start of the attack and strong intensity dependence of auditory evoked potentials. These findings substantiate migraine sufferers as having an abnormal trait interictally, with the attack characterized by a change in the state of central processing. Exploitation of these differences may be a useful tool to study the mechanism of action of drugs used for the treatment of migraine.

Visual Spatial Attention in Migraine Sufferers in Postictal and Interictal Phases: An Event-Related Potential Study

Migraineurs with and without aura (MWAs and MWOAs) as well as controls were measured twice with an interval of 7 days. The first session of recordings and tests for migraineurs was held about 7 hours after a migraine attack. We hypothesized that electrophysiological changes in the posterior cerebral cortex related to visual spatial attention are influenced by the level of arousal in migraineurs with aura, and that this varies over the course of time. ERPs related to the active visual attention task manifested significant differences between controls and both types of migraine sufferers for the N200, suggesting a common pathophysiological mechanism for migraineurs. Furthermore, migraineurs without aura (MWOAs) showed a significant enhancement for the N200 at the second session, indicating the relevance of time of measurement within migraine studies. Finally, migraineurs with aura (MWAs) showed significantly enhanced P240 and P300 components at central and parietal cortical sites compared to MWOAs and controls, which seemed to be maintained over both sessions and could be indicative of increased noradrenergic activity in MWAs.

Aminergic tone correlates of migraine and tension-type headache: a study using the tridimensional personality questionnaire

BACKGROUND

Aminergic neurotransmitter activity has been studied in many neuropsychiatric diseases by means of a self-administered questionnaire proposed by Cloninger. Given that central aminergic modulation plays a major role in the pathophysiology of primary headaches, we investigated the personality dimensions related to aminergic neurotransmitter activity in patients with migraine and tension-type headache.

METHODS

From a consecutive series of 230 patients, we selected those presenting with migraine and tension-type headache according to the International Headache Society criteria. All patients were assessed by means of the Cloninger 100-item self-report Tridimensional Personality Questionnaire and a depression scale. The four dimensions of personality are novelty seeking (dopaminergic), harm avoidance (serotonergic), reward dependence (noradrenergic), and persistence (glutaminergic).

RESULTS

One hundred twenty-one patients presenting with migraine and 42 with tension-type headache were recruited. The results indicate significantly higher harm avoidance scores (P<.001) in both patients with migraine and those with tension-type headache than in controls. Furthermore, patients with migraine had a significantly low score in the novelty seeking dimension (P<.001). When we compared only the two groups of patients with headache, we found that the persistence dimension alone was significantly higher in patients with migraine than in those with tension-type headache (P<.05). No differences were observed either in the overall scores of the other personality dimensions or in the depression scale scores.

CONCLUSIONS

The Tridimensional Personality Questionnaire results support a role of the serotonergic system in both migraine and tension-type headache pathophysiology. A dysfunction of dopaminergic and glutaminergic tone seems to be a specific feature of migraine.

Plasma and platelet amino acid concentrations in patients affected by major depression and under fluvoxamine treatment

Plasma and platelet levels of 18 amino acids were measured in 29 outpatients (mean age +/- SD 47.41 +/- 10.85 years; 14 F, 15 M) affected by major depression (DSM IV) and in 28 healthy volunteers (mean age 42.46 +/- 14.19 years; 12 F, 16 M). Plasma and platelet levels of amino acids tended to be higher in depressed patients than in healthy controls. In particular, glutamate, taurine and lysine plasma levels and aspartate, serine and lysine platelet levels were significantly higher. Tryptophan/large neutral amino acids ratio (trp/LNAAs) was significantly lower in depressed patients. Fluvoxamine treatment did not influence plasma and platelet levels of amino acids or trp/LNAAs ratio.

Auditory evoked potentials in the assessment of central nervous system effects of antimigraine drugs

Because the "intensity dependence" of cortical auditory evoked potentials (IDAP) is under serotonergic control, it can be used to assess central antimigraine effects of 5HT1B/1D agonists. We measured IDAP before and 2 h after naratriptan (5 mg, n = 19) and zolmitriptan (5 mg, n = 19) in healthy volunteers. IDAP was expressed as the amplitude-stimulus intensity function ("ASF slope"). Naratriptan tended to increase ASF slope (mean difference 0.23 +/- 0.62 microV/10 dB, p = 0.06) while zolmitriptan (0.08 +/- 0.95 microV/10 dB, p = 0.35) did not. We assessed the suitability of IDAP for measuring central antimigraine drug effects using repeatability data (see companion paper). We calculated the trade-off between the size of the expected drug effects (ASF slope difference) and the necessary sample size. Because of poor repeatability 36 to 80 subjects are required to detect ASF slope changes in the 0.25-0.5 microV/10 dB range. These data can be used to design trials using IDAP.

Epidemiology and pathogenesis of posttraumatic headache

This article presents an overview of the epidemiology and pathophysiology of posttraumatic headache. It reviews definitions of mild head injury (MHI), mild traumatic brain injury (MTBI), and concussion, and discusses the confusion that often occurs with these terms. Headache types and their pathophysiology are examined in detail. Just as the exact pathophysiology is unknown for migraine and other types of headache, the exact pathophysiology of headache after trauma is also still unknown in many cases. Possible connections between head or neck injuries and headache are reviewed, as well as hypothesized neurochemical changes that may occur in both migraine and traumatic brain injury (TBI). Psychological and legal factors are also considered.

Effectiveness of lamotrigine in the prophylaxis of migraine with aura: an open pilot study

We report a small open pilot study to evaluate the efficacy of lamotrigine (100 mg/day) in the prevention of migraine with aura attacks. We studied 24 patients affected by migraine with aura with a high frequency of attacks. Following a 1-month run-in period, the patients took lamotrigine for 3 months. Mean attack number per month was reduced from 6.1 +/- 4.1 during the run-in period to 0.7 +/- 1.3 at the 3rd month of treatment (p < 0.0001). In 13 out of 21 patients who completed the study, the attacks were completely abolished at the 3rd month of treatment, while only one patient was completely unresponsive to the drug. Lamotrigine seems worthy of a controlled trial as prophylaxis of a migraine with aura.

Plasma levels of neuroexcitatory amino acids in patients with migraine or tension headache

Plasma amino acids were analysed in patients with migraine with (9) and without (80) aura, in patients with tension headache (14) and in controls (62). The neuroexcitatory amino acids glutamic acid, glutamine, glycine, cysteic acid and homocysteic acid were elevated in migraine patients while total thiols (cysteine/cystine) were reduced. Patients with tension headache had values which were similar to those of controls. Tryptophan was elevated in migraine patients without aura only. Studies on two patients showed that the raised resting excitatory amino acid levels became still further elevated during a migraine attack. These results show that high concentrations of neurotransmitter amino acids occur normally in migraine patients and suggest that this profile may be a contributory factor in migraine attacks. Tension headache, however, has different biochemical parameters.