Serotonin and migraine: a reconsideration of the central theory

Understanding the Biological Relationship between Migraine and Depression

Migraine is a highly prevalent neurological disorder. Among the risk factors identified, psychiatric comorbidities, such as depression, seem to play an important role in its onset and clinical course. Patients with migraine are 2.5 times more likely to develop a depressive disorder; this risk becomes even higher in patients suffering from chronic migraine or migraine with aura. This relationship is bidirectional, since depression also predicts an earlier/worse onset of migraine, increasing the risk of migraine chronicity and, consequently, requiring a higher healthcare expenditure compared to migraine alone. All these data suggest that migraine and depression may share overlapping biological mechanisms. Herein, this review explores this topic in further detail: firstly, by introducing the common epidemiological and risk factors for this comorbidity; secondly, by focusing on providing the cumulative evidence of common biological aspects, with a particular emphasis on the serotoninergic system, neuropeptides such as calcitonin-gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP), substance P, neuropeptide Y and orexins, sexual hormones, and the immune system; lastly, by remarking on the future challenges required to elucidate the etiopathological mechanisms of migraine and depression and providing updated information regarding new key targets for the pharmacological treatment of these clinical entities.

Imaging Correlates between Headache and Breast Cancer: An [18F]FDG PET Study

This study aimed to examine brain metabolic patterns on [18F]Fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET) in breast cancer (BC), comparing patients with tension-type headache (TTH), migraine (MiG), and those without headache. Further association with BC response to neoadjuvant chemotherapy (NAC) was explored. In this prospective study, BC patients eligible for NAC performed total-body [18F]FDG PET/CT with a dedicated brain scan. A voxel-wise analysis (two-sample t-test) and a multiple regression model were used to compare brain metabolic patterns among TTH, MiG, and no-headache patients and to correlate them with clinical covariates. A single-subject analysis compared each patient's brain uptake before and after NAC with a healthy control group. Primary headache was diagnosed in 39/46 of BC patients (39% TTH and 46% MiG). TTH patients exhibited hypometabolism in specific brain regions before NAC. TTH patients with a pathological complete response (pCR) to NAC showed hypermetabolic brain regions in the anterior medial frontal cortex. The correlation between tumor uptake and brain metabolism varied before and after NAC, suggesting an inverse relationship. Additionally, the single-subject analysis revealed that hypometabolic brain regions were not present after NAC. Primary headache, especially MiG, was associated with a better response to NAC. These findings suggest complex interactions between BC, headache, and hormonal status, warranting further investigation in larger prospective cohorts.

Self-administration of Psilocybin for the Acute Treatment of Migraine: A Case Report

Background

Migraine is a common neurovascular disorder with a pathophysiology related to the serotonin (5-hydroxytryptamine; 5-HT) system. Pharmacologic modulation of 5-HT receptors has demonstrated efficacy in the acute treatment of migraines. Psilocybin, a classic psychedelic with 5-HT receptor activity, has demonstrated therapeutic potential in the management of neuropsychiatric conditions. To date, no reports have investigated the effect of psilocybin administered acutely during a migraine episode.

Case presentation

The case of a 33-year-old male patient with a history of migraines with aura, who had acute administration of oral psilocybin (in the form of the dried fruiting body of Psilocybe cubensis mushrooms) at migraine onset is presented. Headache intensity was rated hourly using the Numerical Rating Scale (NRS) and compared to three previous migraines. Profound reductions in headache intensity and emetic episodes were reported during the migraine treated acutely with oral psilocybin administration, compared to three previous migraines.

Discussion

The severe, disabling, and treatment-resistant nature of migraines warrants continued surveillance for novel pharmacologic interventions. The established congruous pathophysiology of migraine and pharmacology of psilocybin, via the 5-HT receptor system, positions psilocybin as a potential therapeutic target.

Conclusion

While this report highlights the potential role of psilocybin in the acute management of migraines, it is essential to note that it should not be considered a basis for guiding clinical practice at this point. Further research is necessary to establish the safety and efficacy of psilocybin as a treatment option for migraines.

Migraine and obesity: what is the real direction of their association?

INTRODUCTION

In recent decades, studies have addressed the issue of how migraine and obesity are related and have suggested obesity as a risk factor for migraine headache. However, the exact direction of this relationship remains under debate. In this review, the authors summarize the evidence that have suggested migraine as a risk factor for obesity and overweightness.

AREAS COVERED

This article reviews the results of the previous research published on PubMed and Scopus databases (from 2000 to 2020) concerning the association between migraine and obesity to determine the actual direction of their association. Special attention has been given to the common mechanistic pathways involved in the pathophysiology of migraine and obesity.

EXPERT OPINION

The majority of research conducted thus far has considered obesity as a risk factor for migraine. However, because of the cross-sectional design of available research, we cannot be certain of the proposed direction of this association. There is evidence supporting the hypothesis that obesity can serve as a consequence of migraine through the effects of neuropeptides, inflammatory mediators, adipokines, gut microbiota and modifications in eating behavior and lifestyle. However, the real direction of the relationship between migraine and obesity should be further investigated in large prospective studies.

Associations of migraines with suicide ideation or attempts: A meta-analysis

Objective

Whether migraine is associated with a higher risk of suicide ideation and/or attempts remains controversial. Therefore, we aimed to evaluate these potential associations in migraine patients by performing a meta-analysis of previously published data.

Methods

We searched for studies published up to 31 June 2022 that compared the risk of suicide ideation/attempt in migraineurs and non-migraineurs in PubMed, EMBASE, and Web of Science databases. Sixteen studies fulfilled the eligibility criteria. We applied Random-effects models to calculate pooled adjusted odds ratios (AORs) and 95% confidence intervals (CIs) in patients with migraine.

Results

Migraine patients were at a significantly increased risk of suicide ideation (AOR 1.33, 95% CI 1.15-1.54) and suicide attempts (AOR 1.70, 95% CI 1.42-2.03). The increase in risk may be greater in adults (>19 years) than in younger individuals.

Conclusion

The available evidence indicates a significant association of migraines with suicide ideation and attempts. Future work should confirm and extend these findings, as well as explore whether they are affected by ethnicity or geography.

The Pathophysiological Relationship Between Migraine and SARS-CoV-2 Infection: A Comprehensive Literature Review

People with migraine, and individuals with other neurological conditions, have suffered in multiple aspects during the COVID-19 pandemic. This paper will discuss the factors that impacted the neurology department. The emergence of severe acute respiratory syndrome coronavirus 2 in late 2019 has generated new challenges in healthcare systems across the globe. Similar to the fields of pulmonology and cardiology that saw an increase in research, the neurology department was in search of possible relationships between COVID-19 and other medical conditions. Research on the possible common pathophysiological mechanism between COVID-19 and migraine is currently being studied. The most recent hypothesis suggests the following: migraine is caused by an increased release of calcitonin gene-related peptide from the trigeminal ganglion, which will cause an increase in nitric oxide and IL-1β, resulting in vasodilation and inducing hyperalgesia. COVID-19 causes an increase in nod-like receptor protein 3, which causes the production of IL-1β and again induces an inflammatory response. This review article looks at the mechanisms of migraine and COVID-19, and tries to link a common pathophysiological pathway between the two. This report also serves as a gateway for further research regarding possible management that could potentially target both of these mechanisms.

Bidirectional Association Between Fibromyalgia and Migraine Among Probands and Unaffected Non-Twin Siblings: A Nationwide Population-Based Study

OBJECTIVE

This study explored the bidirectional relationship between fibromyalgia and migraine among probands with either of the two disorders and their unaffected siblings.

BACKGROUND

Evidence suggests a bidirectional association between fibromyalgia and migraine in individuals and in twins. However, whether a bidirectional association between fibromyalgia and migraine also occurs among siblings remains unknown.

METHODS

Using the Taiwan National Health Insurance Research Database, we examined the data of 2677 probands with fibromyalgia, 2780 unaffected siblings, and 11120 matched controls to assess the risk of migraine. In contrast, 1830 probands with migraine, 1936 unaffected siblings, and 7744 matched controls to assess the risk of fibromyalgia.

RESULTS

Logistic regression analyses demonstrated that patients with fibromyalgia (odds ratio [OR]: 3.69; 95% confidence interval [CI]: 2.87-4.74) and unaffected siblings (OR: 1.51; 95% CI: 1.08-2.10) were more likely to develop migraine than the controls during the follow-up period. Moreover, patients with migraine and unaffected siblings had a 4.86-fold (95% CI: 3.86-6.09) and 1.59-fold (95% CI: 1.18-2.12) increased risk of fibromyalgia than the controls.

CONCLUSION

The bidirectional association between fibromyalgia and migraine among probands and unaffected siblings suggests a familial coaggregation of these two conditions. Additional studies are required to investigate the genetic and environmental etiologies for this coaggregation.

Citalopram Neuroendocrine Challenge Shows Altered Tryptophan and Kynurenine Metabolism in Migraine

Altered tryptophan (TRP) metabolism may have an important role in migraine susceptibility through its main metabolites, serotonin and kynurenine (KYN). Both affect pain processing and stress response by interfering with neural and brain hypersensitivity and by interacting with chemokines and cytokines that control vascular and inflammatory processes. The involvement of these pathways in migraine has been widely studied, but acute citalopram neuroendocrine challenge on TRP metabolism and cytokine profile has not been investigated yet. In our study, females with episodic migraine without aura and healthy controls were studied before and after acute citalopram or placebo in a double-blind setting. At baseline, increased TRP/large neutral amino acid (LNAA) ratio and decreased RANTES chemokine concentration were detected in migraine patients compared to controls. The challenge induced a significant increase in TRP, KYN, and TRP/LNAA in healthy controls, but not in migraine patients. Furthermore, migraine attack frequency negatively correlated with KYN/TRP ratio and positively correlated with the neuroendocrine-challenge-induced KYN concentration increase. Our results support a decreased breakdown of TRP via KYN pathway and a failure to modulate TRP–KYN pathway during citalopram-induced acute stress together with an increased vascular sensitivity in migraine. These mechanisms may provide useful drug targets for future drug development.

5-hydroxytryptamine in migraine: The puzzling role of ionotropic 5-HT3 receptor in the context of established therapeutic effect of metabotropic 5-HT1 subtypes

5-hydroxytryptamine (5-HT; serotonin) is traditionally considered as a key mediator implicated in migraine. Multiple 5-HT receptor subtypes contribute to a variety of region-specific functional effects. The raphé nuclei control nociceptive inputs by releasing 5-HT in the brainstem, whereas dural mast cells provide the humoral source of 5-HT in the meninges. Triptans (5-HT_1B/D agonists) and ditans (5-HT_1F agonists) are the best established 5-HT anti-migraine agents. However, activation of meningeal afferents via ionotropic 5-HT₃ receptors results in long-lasting excitatory drive suggesting a pro-nociceptive role for these receptors in migraine. Nevertheless, clinical data do not clearly support the applicability of currently available 5-HT₃ antagonists to migraine treatment. The reasons for this might be the presence of 5-HT₃ receptors on inhibitory interneurons dampening the excitatory drive, a lack of 5-HT₃ A-E subunit-selective antagonists and gender/age-dependent effects. This review is focusing on the controversial role of 5-HT₃ receptors in migraine pathology and related pharmacological perspectives of 5-HT ligands.

Migraine pharmacology and brain ischemia

Introduction: The aim of this review article was to analyze in details the mechanism of drugs’ effects in the treatment and prevention of a migraine attack, as well as to discuss the hypotheses of migraine pathogenesis.

Migraine attack treatment agents: The main agents for migraine attack treatment have an anti-nociceptive activity.

Agents for migraine preventive treatment: β-blocker propranolol also has anti-serotonin and analgesic activities, and most drugs used for the prophylactic treatment of migraine have a vasodilating activity.

Vascular hypothesis of migraine pathogenesis: Despite numerous studies that have expanded our understanding of migraine pathogenesis, the importance of the vascular component in the pathogenesis of this disease has not questioned yet.

Neurogenic hypotheses of cortical spreading depression: It is necessary to take into account the points of this hypothesis in the context of the pathophysiology of migraine.

Neurochemical serotonin hypotheses of migraine pathogenesis: Serotonin plays an important role in the pathogenesis of migraine.

Trigemino-vascular hypotheses of migraine pathogenesis: The trigemino-vascular hypothesis claims to solve the problem of migraine pain.

Migraine and ischemic brain damage: Migraine is a risk factor for ischemic stroke and cognitive disorders.

Search for the new anti-ischemic anti-migraine preparations: A methodology for the search for new anti-ischemic anti-serotonin drugs for the treatment of migraine is proposed.

Conclusion: Belonging of a drug to one or another pharmacological group does not always correspond to its therapeutic effect on the pathogenetic processes of migraine. Migraine with its variety of forms cannot fit only one of the proposed hypotheses on the pathogenesis of this disease.

Graphical abstract:

Determining 5HT7R's Involvement in Modifying the Antihyperalgesic Effects of Electroacupuncture on Rats With Recurrent Migraine

Electroacupuncture (EA) is widely used in clinical practice to relieve migraine pain. 5-HT₇ receptor (5-HT₇R) has been reported to play an excitatory role in neuronal systems and regulate hyperalgesic pain and neurogenic inflammation. 5-HT₇R could influence phosphorylation of protein kinase A (PKA)- or extracellular signal-regulated kinase_{1 / 2} (ERK_{1 / 2})-mediated signaling pathways, which mediate sensitization of nociceptive neurons via interacting with cyclic adenosine monophosphate (cAMP). In this study, we evaluated the role of 5-HT₇R in the antihyperalgesic effects of EA and the underlying mechanism through regulation of PKA and ERK_{1 / 2} in trigeminal ganglion (TG) and trigeminal nucleus caudalis (TNC). Hyperalgesia was induced in rats with dural injection of inflammatory soup (IS) to cause meningeal neurogenic inflammatory pain. Electroacupuncture was applied for 15 min every other day before IS injection. Von Frey filaments, tail-flick, hot-plate, and cold-plated tests were used to evaluate the mechanical and thermal hyperalgesia. Neuronal hyperexcitability in TNC was studied by an electrophysiological technique. The 5-HT₇R antagonist (SB269970) or 5-HT₇R agonist (AS19) was administered intrathecally before each IS application at 2-day intervals during the 7-day injection protocol. The changes in 5-HT₇R and 5-HT₇R-associated signaling pathway were examined by real-time polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) analyses. When compared with IS group, mechanical and thermal pain thresholds of the IS + EA group were significantly increased. Furthermore, EA prevented the enhancement of both spontaneous activity and evoked responses of second-order trigeminovascular neurons in TNC. Remarkable decreases in 5-HT₇R mRNA expression and protein levels were detected in the IS + EA group. More importantly, 5-HT₇R agonist AS19 impaired the antihyperalgesic effects of EA on p-PKA and p-ERK_{1 / 2}. Injecting 5-HT₇R antagonist SB-269970 into the intrathecal space of IS rats mimicked the effects of EA antihyperalgesia and inhibited p-PKA and p-ERK_{1 / 2}. Our findings indicate that 5-HT₇R mediates the antihyperalgesic effects of EA on IS-induced migraine pain by regulating PKA and ERK_{1 / 2} in TG and TNC.

Does serotonin deficiency lead to anosmia, ageusia, dysfunctional chemesthesis and increased severity of illness in COVID-19?

Different mechanisms forwarded to understand anosmia and ageusia in coronavirus patients are not adequate to explain reversible anosmia and ageusia, which are resolved quickly. In addition, the reason behind the impaired chemesthetic sensations in some coronavirus patients remains unknown. In the present paper it is proposed that SARS-CoV-2 patients suffer from depletion of tryptophan, as ACE2, a key element in the process of absorption of tryptophan from the food, is significantly reduced in the patients as coronavirus uses ACE2 as the receptor to enter the host cells. The tryptophan depletion leads to a deficit of serotonin (5-HT) in SARS-COV-2 patients because tryptophan is the precursor in the synthesis of 5-HT. Such 5-HT deficiency can explain anosmia, ageusia and dysfunctional chemesthesis in COVID-19, given the fact that 5-HT is an important neuromodulator in the olfactory neurons, taste receptor cells and transient receptor potential channels (TRP channels) involved in chemesthesis. In addition, 5-HT deficiency worsens silent hypoxemia and depresses hypoxic pulmonary vasoconstriction leading to increased severity of the disease. Also, the levels of anti-inflammatory melatonin (synthesized from 5-HT) and nicotinamide adenine dinucleotide (NAD⁺, produced from niacin whose precursor is the tryptophan) might decrease in coronavirus patients resulting in the aggravation of the disease. Interestingly, selective serotonin reuptake inhibitors (SSRIs) may not be of much help in correcting the 5-HT deficiency in COVID-19 patients, as their efficacy goes down significantly when there is depletion of tryptophan in the system. Hence, tryptophan supplementation may herald a radical change in the treatment of COVID-19 and accordingly, clinical trials (therapeutic / prophylactic) should be conducted on coronavirus patients to find out how tryptophan supplementation (oral or parenteral, the latter in severe cases where there is hardly any absorption of tryptophan from the food) helps in curing, relieving or preventing the olfactory, gustatory and chemesthetic dysfunctions and in lessening the severity of the disease.

Headaches in Adults in Primary Care: Evaluation, Diagnosis, and Treatment

Headaches are common in primary care. The diagnosis is made by a careful history and physical examination. Imaging is generally not warranted. Several general principles underlie the acute treatment of headache: early initiation of therapy and adequate dosing at first dose. Careful attention to avoiding too frequent administration of acute therapy is important to avoid medication overuse headaches. Opioids should always be avoided. Preventive treatment is indicated for frequent headaches. Successful treatment entails low-dose medication with careful titration and monitoring of headache frequency. Behavioral strategies are important and should be part of any comprehensive headache management plan.

Impacts of migraine on the prevalence and clinical presentation of depression: A population-based study

BACKGROUND

A close association has been reported between depression and migraine. However, information concerning the impacts of migraine on the clinical presentation and prevalence of depression in a population-based study is currently limited.

METHODS

Data from the Korean Headache-Sleep Study, a nationwide survey about headache and sleep for adults aged 19-69 years were used. Depression was defined when Patient Health Questionnaire-9 score ≥ 10.

RESULTS

Of 2,695 participants who included in this study, 116 (4.3%), 143 (5.3%), and 1130 (41.9%) had depression, migraine, and non-migraine headache, respectively. Migraine (24/116 [20.5%] vs. 119/2579 [4.7%], p < 0.001) and non-migraine headache (67/116 [58.1%] vs. 1063/2579 [41.3%], p < 0.001) was more prevalent in the group of participants with depression than among participants without depression. Among participants with depression, there was no statistically differences in total Patient Health Questionnaire-9 (PHQ-9) scores among migraine, non-migraine headache, and non-headache groups (median with interquartile range, 12.0 [10.2-18.0] vs. 13.0 [11.0-16.0] vs. 12.0 [10.0-15.2], p = 0.514). Among subcomponent scores of PHQ-9, all subcomponent scores did not significantly differ by headache status except feeling tired or having little energy scores (non-migraine headache 2.0 [2.0-3.0] vs. non-headache 2.0 [1.0-2.0], p = 0.010).

LIMITATIONS

Diagnosis of depression based on PHQ-9 questionnaire and small sample size in subgroup analyses.

CONCLUSIONS

Participants with depression exhibit an increased risk of migraine and non-migraine headache compared with participants without depression. Among participants with depression, the severity of depression did not significantly differ on the basis of headache status.

Is There an Association Between Migraine and Major Depressive Disorder? A Narrative Review

Various studies on the association of migraine with depression are published. The comorbidity may upgrade health conditions up to a critical degree. Besides, the duration of symptoms and treatment may be prolonged. Moreover, these conditions can force substantial financial and social hardships on patients and their families. In this literature review, we intend to examine the evidence obtained on the possible associations between migraine and major depressive disorder (MDD). This review is focused on aminergic neurons. One of the variables associated with patients who experience both of these two diseases might have a history of assault. In migraine and MDD patients, genetic evidence, such as single nucleotide polymorphisms (SNP), was found to be one of the associations. Another theory concluded that actual headache diagnosed in patients who received no treatment manifests a history of anxiety, and later, the patients display severe somatic symptoms. In conclusion, there is a robust molecular genetic background, explaining the relationship between migraines and MDD. This correlated data renders a combination of both diagnoses as single separate entities. However, further studies are encouraged to point out the issue of treatment strategies.

Ultra-rapid brain uptake of subcutaneous sumatriptan in the rat: Implication for cluster headache treatment

BACKGROUND

In spite of the substantial therapeutic efficacy of triptans, their site of action is still debated. Subcutaneous sumatriptan is the most efficacious symptomatic treatment for cluster headache (CH) patients, showing therapeutic onset within a few minutes after injection even in migraine patients. However, whether subcutaneous sumatriptan is able to reach the CNS within this short time frame is currently unknown.

METHODS

Here, by means of liquid chromatography/mass spectrometry, we investigated peripheral and brain distribution of subcutaneous sumatriptan soon after injection in rats at a dose equivalent to that used in patients. Tissue sumatriptan contents were compared to those of oxazepam, a prototypical lipophilic, neuroactive drug.

RESULTS

We report that sumatriptan accumulated within brain regions of relevance to migraine and CH pathogenesis such as the hypothalamus and the brainstem as soon as 1 and 5 minutes after injection. Notably, sumatriptan brain distribution was faster than that of oxazepam, reaching concentrations exceeding its reported binding affinity for 5HT1_B/D receptors, and in the range of those able to inhibit neurotransmitter release in vivo.

CONCLUSION

Our findings indicate that sumatriptan distributes within the CNS soon after injection, and are in line with prompt pain relief by parenteral sumatriptan in CH patients.

Increased activation of the pregenual anterior cingulate cortex to citalopram challenge in migraine: an fMRI study

Background

The anterior cingulate cortex (ACC) is a key structure of the pain processing network. Several structural and functional alterations of this brain area have been found in migraine. In addition, altered serotonergic neurotransmission has been repeatedly implicated in the pathophysiology of migraine, although the exact mechanism is not known. Thus, our aim was to investigate the relationship between acute increase of brain serotonin (5-HT) level and the activation changes of the ACC using pharmacological challenge MRI (phMRI) in migraine patients and healthy controls.

Methods

Twenty-seven pain-free healthy controls and six migraine without aura patients participated in the study. All participant attended to two phMRI sessions during which intravenous citalopram, a selective serotonin reuptake inhibitor (SSRI), or placebo (normal saline) was administered. We used region of interest analysis of ACC to compere the citalopram evoked activation changes of this area between patients and healthy participants.

Results

Significant difference in ACC activation was found between control and patient groups in the right pregenual ACC (pgACC) during and after citalopram infusion compared to placebo. The extracted time-series showed that pgACC activation increased in migraine patients compared to controls, especially in the first 8–10 min of citalopram infusion.

Conclusions

Our results demonstrate that a small increase in 5-HT levels can lead to increased phMRI signal in the pregenual part of the ACC that is involved in processing emotional aspects of pain. This increased sensitivity of the pgACC to increased 5-HT in migraine may contribute to recurring headache attacks and increased stress-sensitivity in migraine.

An attention bias test to assess anxiety states in laying hens

Fear is a response to a known threat, anxiety is a response to a perceived threat. Both of these affective states can be detrimental to animal welfare in modern housing environments. In comparison to the well-validated tests for assessing fear in laying hens, tests for measuring anxiety are less developed. Perception of a threat can result in an attention bias that may indicate anxious affective states in individual hens following playback of an alarm call. In Experiment 1, an attention bias test was applied to hens that differed in their range access to show that hens that never ranged were more vigilant (stretching of the neck and looking around: P < 0.001) and slower to feed following the second alarm call playback (P = 0.01) compared with hens that ranged daily. All hens showed a reduction in comb temperature following the first alarm call (P < 0.001). In Experiment 2, an open field test was used to determine an effective dose of 2 mg/kg for the anxiogenic drug meta-Chlorophenylpiperazine (m-CPP) in adult laying hens. Hens dosed with 2 mg/kg showed reduced locomotion compared with a saline solution (P < 0.05). In Experiment 3, 2 mg/kg m-CPP or saline was administered to adult hens previously habituated to the open field arena to pharmacologically validate an attention bias test as a measure of anxiety. Hens dosed with m-CPP were slower to feed (P = 0.02) and faster to vocalize following a second alarm call playback (P = 0.03) but these hens did not exhibit the same vigilance behavior as documented in Experiment 1. The m-CPP hens also spent more time stepping and vocalizing (both P < 0.001) than the saline hens. An attention bias test could be used to assess anxiety. However, behavioral responses of hens may vary depending on their age or test environment familiarity, thus further refinement of the test is required. In these tests, 2 mg/kg of m-CPP resulted in motionless behavior when the environment was novel, but more movement and vocalizing when the environment was familiar. The extreme behavioral phenotypes exhibited by individually-tested birds may both be indicators of negative states.

Relating excitatory and inhibitory neurochemicals to visual perception: A magnetic resonance study of occipital cortex between migraine events

Certain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

The association between dietary tryptophan intake and migraine

Migraineurs have been identified to have chronically decreased serotonin levels while its concentrations markedly increase during ictal periods. Regarding the importance of adequate tryptophan intake in regulating serotonin homeostasis and subsequent effect on migraine attacks, we designed the current study. The migraine group (n = 514, diagnosed according to the ICHDIII criteria) was recruited from a tertiary headache clinic. The controls consisted of 582 sex-matched healthy volunteers who were randomly selected from general population. After collecting demographic and anthropometric data, a validated 168-item semi-quantitative food frequency questionnaire (FFQ) was used for dietary intake assessments. Multiple regression models were applied to explore the relationship between migraine and tryptophan intake. The mean (SD) of the age of participants in the controls and migraine group was 44.85 (13.84) and 36.20 (9.78) years, respectively. The multiple regression models were adjusted for age (year), sex, body mass index (BMI) (kg/m²), total daily energy intake (kcal/day), dietary intakes of total carbohydrates (g/day), animal-based protein (g/day), plant-based protein (g/day), total fat (g/day), saturated fat (g/day), and cholesterol (mg/day). It was shown that there is a negative association between tryptophan intake and migraine risk ((OR in the 3rd quartile = 0.46; 95% CI = 0.25-0.85) (OR in the 4th quartile = 0.40; 95% CI = 0.16-0.98) compared with the first quartile; P for trend = 0.045). Therefore, our results showed that subjects who had a median intake of 0.84-1.06 g of tryptophan per day had reduced odds of developing migraine by approximately 54-60%, relative to those consumed ≤ 0.56 g/day.

Alkaloids from the rhizomes of Ligusticum striatum exert antimigraine effects through regulating 5-HT1B receptor and c-Jun

ETHNOPHARMACOLOGICAL RELEVANCE

Migraine is a prevalent, complex, painful, and disabling neurovascular disorder that places an enormous social and economic burden on patients. Rhizome Chuanxiong (RCX), the dried rhizomes of Ligusticum striatum DC., has been widely used in the clinic for the treatment of migraine for centuries in China. Total alkaloids (TAs) are considered to be important effective ingredients of L. striatum, especially for cardiovascular and cerebrovascular diseases. However, there has been no study published, to date, reporting the antimigraine effects of TAs from RCX (RCXTAs).

AIM OF THE STUDY

The present study was designed to evaluate the antimigraine effects of RCXTAs and explore the underlying mechanisms in an experimental migraine rat model.

MATERIALS AND METHODS

RCXTAs were prepared in accordance with our previous optimized preparation process. A nitroglycerin-induced migraine model in rats and a reserpine-induced migraine model in mice were established to investigate the effects of RCXTAs on monoamine neurotransmitters in brain tissue, including 5-hydroxytryptamine (5-HT) and its metabolite (5-HIAA). Migraine rats or mice were divided into six groups as follows: control; model; zolmitriptan (1.67 mg/kg); and low-, medium-, and high-dose RCXTAs (12.5, 25, and 50 mg/kg, respectively). The levels of 5-HT and 5-HIAA in the brains of rats and mice were determined by using the enzyme-linked immunosorbent assay method. Pathological changes in the brains of migraine rats were examined by immunohistochemistry. The protein expression of 5-HT_1B receptor, c-Fos, and c-Jun in the periaqueductal gray (PAG) of migraine rats was measured by Western blot.

RESULTS

After preventive administration of RCXTAs to the nitroglycerin-induced migraine rats, the levels of 5-HT and 5-HIAA in the brain tissue were generally upregulated in all three RCXTA dose groups, a finding that was similar to that observed in the control group. Additionally, the 5-HT and 5-HIAA levels were significantly increased in the medium- and high-dose RCXTA groups when compared with the model group (p < 0.01). Therapeutical administration of RCXTAs to reserpine-induced migraine mice also inhibited the reduction of 5-HT and 5-HIAA in the brain (p < 0.01). Both immunohistochemistry and Western blot tests showed that RCXTAs pretreatment has significantly upregulated 5-HT_1B receptor expression and downregulated c-Jun expression in the nitroglycerin-induced migraine rats.

CONCLUSIONS

RCXTAs exerted significant preventive and therapeutic effects on migraine via increasing the levels of 5-HT and 5-HIAA. Upregulation of the expression of monoamine neurotransmitter 5-HT_1B receptor and downregulation of the expression of c-Jun were the possible mechanisms.

Lifestyle - A Common Denominator for the Onset and Management of Migraine Headache: Complementing Traditional Approaches with Scientific Evidence

Background:

Ayurveda and Yoga have gained popularity in the management of various chronic health problems associated with pain including migraine headache. It is evident from both scientific as well as traditional literature that stress, diet, sleep, and exposure to extreme climatic conditions act as triggering factors for the onset of migraine. Hence, it is essential to focus on lifestyle including diet as important factors for prevention and as adjuvant factors in the management of migraine headache.

Aim:

The aim was to propose a new perspective to the understanding of migraine headache keeping in view the role of lifestyle including diet.

Methods:

Classical Ayurveda texts and traditional Yoga scriptures were used to compile information on the role of lifestyle including diet in the onset and management of migraine headache. This was complemented by PubMed-based review of scientific literature.

Outcome:

Ayurveda texts provide an extensive information about the basic understanding, causes, precipitating factors, and management of migraine headache, while Yoga texts refer to the concept of mental stress (adhi) leading to physical health problems (vyadhi). It is evident from the literature that diet, sleep, exposure to extreme climatic conditions, and mental stress play an important role in the onset and management of migraine headache.

Conclusion:

Lifestyle appears to be the common factor for both onset and management of migraine headache.

The Burden of Migraine in Adults with Atrial Septal Defect: A Nationwide Cohort Study

We aimed to investigate migraine diagnoses in a hospital setting, use of prescription migraine medicine and levels of serotonin in patients with atrial septal defect. Using Danish national registries to identify all patients born before 1994 diagnosed with atrial septal defect between 1959 and 2013, thus including 2277 patients and a gender and age matched comparison cohort of 22756. Plasma serotonin was measured in 136 patients with a small, unclosed, atrial septal defects and 18 controls. Patients with atrial septal defect had an increased risk of receiving a migraine diagnosis (HR 3.4 (95% CI: 2.6–4.6)) and receiving migraine medicine (HR 1.8 (95% CI: 1.2–2.5)). Ten years after closure, 93% of those using migraine medicine pre-closure, were still receiving this. The risk of having very high plasma serotonin levels was increased in patients with atrial septal defect compared with the control group, but there was no difference in the median values between the two groups. Migraine and use of migraine medicine were increased in atrial septal defect patients. The use of medicine was not diminished by closure of the defect. Plasma serotonin was severely elevated in 18% of the patients with atrial septal defect.

Bidirectional association between migraine and fibromyalgia: retrospective cohort analyses of two populations

OBJECTIVE

Fibromyalgia (FM) and migraine are common pain disorders that tend to coexist. This study determined whether these two conditions exhibited any mutual influences.

SETTING

Cohort study.

PARTICIPANTS

A retrospective, longitudinal cohort study was conducted using data obtained from a nationwide healthcare database. This study had two arms. Arm 1 comprised 33 216 patients with FM and arm 2 consisted of 7420 patients with migraine; all of these patients were diagnosed between 2000 and 2010. Using the aforementioned database, control subjects who had neither FM nor migraine and were matched with the FM and migraine patients by sex, age and index date of diagnosis were recruited. Each control cohort was four times the size of the corresponding study cohort. Follow-up for the control and study cohorts was conducted until the end of 2011.

RESULTS

The incidence rates of FM and migraine were calculated in arms 1 and 2, respectively. The overall incidence of migraine was greater in the FM cohort than in the corresponding control cohort (4.39 vs 2.07 per 1000 person-years (PY)); crude HR=2.12, 95% CI=1.96 to 2.30; adjusted HR (aHR)=1.89, 95% CI=1.75 to 2.05). After adjustment for sex, age and comorbidities, the overall incidence of FM in the migraine cohort was 1.57 times greater than that in the corresponding control cohort (7.01 vs 4.49 per 1000 PY; aHR=1.52, 95% CI=1.39 to 1.65).

CONCLUSIONS

The present study revealed a bidirectional link between FM and migraine.

Association of Suicide Risk With Headache Frequency Among Migraine Patients With and Without Aura

Background: Migraines with aura have been associated with suicide in adolescents and young adults, but the association between suicide and migraine frequency has not been determined. This study investigated suicidal ideation and suicide attempts among patients with varying frequencies of migraines, with and without auras.

Methods: This cross-sectional study analyzed 528 patients aged between 20 and 60 years from a headache outpatient clinic in Taiwan. All patients completed a set of questionnaires, including a demographic questionnaire, the Migraine Disability Assessment questionnaire, the Hospital Anxiety and Depression Scale, the Beck Depression Inventory, and the Pittsburgh Sleep Quality Index. Suicide risk was evaluated by self-reported lifetime suicidal ideation and attempts. Patients were divided into low-frequency (1–4 days/month), moderate-frequency (5–8 days/month), high-frequency (9–14 days/month), and chronic (≥15 days/month) migraine groups. The association between migraine frequency and suicidality was investigated using multivariable linear regression and logistic regression.

Results: The rates of suicidal ideation and suicide attempts were the highest for chronic migraine with aura (ideation: 47.2%; attempts: 13.9%) and lowest in migraine-free controls (2.8%). Migraine frequency was an independent risk factor for suicidal ideation and attempts in patients with aura (both P_trend < 0.001), but not in patients without auras. Migraine aura and depression were associated with higher risks of suicidal ideation and suicide attempts in patients with migraine.

Conclusion: High migraine frequency has a correlation with high suicide risk in patients who experience an aura, but not in other patients with migraine.

Neurophysiological correlates of clinical improvement after greater occipital nerve (GON) block in chronic migraine: relevance for chronic migraine pathophysiology

BACKGROUND

Therapeutic management of Chronic Migraine (CM), often associated with Medication Overuse Headache (MOH), is chiefly empirical, as no biomarker predicting or correlating with clinical efficacy is available to address therapeutic choices. The present study searched for neurophysiological correlates of Greater Occipital Nerve Block (GON-B) effects in CM.

METHODS

We recruited 17 CM women, of whom 12 with MOH, and 19 healthy volunteers (HV). Patients had no preventive treatment since at least 3 months. After a 30-day baseline, they received a bilateral betamethasone-lidocaine GON-B of which the therapeutic effect was assessed 1 month later. Habituation of visual evoked potentials (VEP) and intensity dependence of auditory evoked potentials (IDAP) were recorded before and 1 week after the GON-B.

RESULTS

At baseline, CM patients had a VEP habituation not different from HV, but a steeper IDAP value than HV (p = 0.01), suggestive of a lower serotonergic tone. GON-B significantly reduced the number of total headache days per month (- 34.9%; p = 0.003). Eight out 17CM patients reversed to episodic migraine and medication overuse resolved in 11 out of 12 patients. One week after the GON-B VEP habituation became lacking respect to baseline (p = 0.01) and to that of HV (p = 0.02) like in episodic migraine, while the IDAP slope significantly flattened (p < 0.0001). GON-B-induced reduction in headache days positively correlated with IDAP slope decrease (rho = 0.51, p = 0.03).

CONCLUSIONS

GON-B may be effective in the treatment of CM, with or without MOH. The pre-treatment IDAP increase is compatible with a weak central serotonergic tone, which is strengthened after GON-B, suggesting that serotonergic mechanisms may play a role in CM and its reversion to episodic migraine. Since the degree of post-treatment IDAP decrease is correlated with clinical improvement, IDAP might be potentially useful as an early predictor of GON-B efficacy.

Diagnosing and Managing Carcinoid Heart Disease in Patients With Neuroendocrine Tumors: An Expert Statement

Carcinoid heart disease is a frequent occurrence in patients with carcinoid syndrome and is responsible for substantial morbidity and mortality. The pathophysiology of carcinoid heart disease is poorly understood; however, chronic exposure to excessive circulating serotonin is considered one of the most important contributing factors. Despite recognition, international consensus guidelines specifically addressing the diagnosis and management of carcinoid heart disease are lacking. Furthermore, there is considerable variation in multiple aspects of screening and management of the disease. The aim of these guidelines was to provide succinct, practical advice on the diagnosis and management of carcinoid heart disease as well as its surveillance. Recommendations and proposed algorithms for the investigation, screening, and management have been developed based on an evidence-based review of the published data and on the expert opinion of a multidisciplinary consensus panel consisting of neuroendocrine tumor experts, including oncologists, gastroenterologists, and endocrinologists, in conjunction with cardiologists and cardiothoracic surgeons.

Serotonergic mechanisms of trigeminal meningeal nociception: Implications for migraine pain

Serotonergic mechanisms play a central role in migraine pathology. However, the region-specific effects of serotonin (5-HT) mediated via multiple types of receptors in the nociceptive system are poorly understood. Using extracellular and patch-clamp recordings, we studied the action of 5-HT on the excitability of peripheral and central terminals of trigeminal afferents. 5-HT evoked long-lasting TTX-sensitive firing in the peripheral terminals of meningeal afferents, the origin site of migraine pain. Cluster analysis revealed that in majority of nociceptive fibers 5-HT induced either transient or persistent spiking activity with prevailing delta and theta rhythms. The 5-HT3-receptor antagonist MDL-72222 or 5-HT1B/D-receptor antagonist GR127935 largely reduced, but their combination completely prevented the excitatory pro-nociceptive action of 5-HT. The 5-HT3 agonist mCPBG activated spikes in MDL-72222-dependent manner but the 5HT-1 receptor agonist sumatriptan did not affect the nociceptive firing. 5-HT also triggered peripheral CGRP release in meninges, which was blocked by MDL-72222.5-HT evoked fast membrane currents and Ca²⁺ transients in a fraction of trigeminal neurons. Immunohistochemistry showed expression of 5-HT3A receptors in fibers innervating meninges. Endogenous release of 5-HT from degranulated mast cells increased nociceptive firing. Low pH but not histamine strongly activated firing. 5-HT reduced monosynaptic inputs from trigeminal Aδ- and C-afferents to the upper cervical lamina I neurons and this effect was blocked by MDL-72222. Consistent with central inhibitory effect, 5-HT reduced CGRP release in the brainstem slices. In conclusion, 5-HT evokes powerful pro-nociceptive peripheral and anti-nociceptive central effects in trigeminal system transmitting migraine pain.

Serotonergic mechanisms in the migraine brain - a systematic review

Background Migraine is one of the most common and disabling of all medical conditions, affecting 16% of the general population, causing huge socioeconomic costs globally. Current available treatment options are inadequate. Serotonin is a key molecule in the neurobiology of migraine, but the exact role of brain serotonergic mechanisms remains a matter of controversy. Methods We systematically searched PubMed for studies investigating the serotonergic system in the migraine brain by either molecular neuroimaging or electrophysiological methods. Results The literature search resulted in 59 papers, of which 13 were eligible for review. The reviewed papers collectively support the notion that migraine patients have alterations in serotonergic neurotransmission. Most likely, migraine patients have a low cerebral serotonin level between attacks, which elevates during a migraine attack. Conclusion This review suggests that novel methods of investigating the serotonergic system in the migraine brain are warranted. Uncovering the serotonergic mechanisms in migraine pathophysiology could prove useful for the development of future migraine drugs.

Rizatriptan overuse promotes hyperalgesia induced by dural inflammatory stimulation in rats by modulation of the serotonin system

Clinical and preclinical studies have implicated serotonin (5-HT) and the 5-HT2A receptor (5-HT2AR) in the pathogenesis of medication-overuse headache (MOH). However, with no appropriate animal model to study this phenomenon it is difficult to differentiate the effects of chronic exposure to analgesics from the consequences of frequent headache attacks during the development of MOH. Therefore, this study used a novel animal model of MOH established by a combination of the overuse of rizatriptan (RIZ) and stimulation with dural inflammatory soup (IS) to investigate whether 5-HT and 5-HT2AR are involved in central plasticity and hyperalgesia. Similar to an IS infusion, IS-RIZ treatment induced nociception-related behaviours in Sprague-Dawley rats and increased Fos expression in the cortex and trigeminal pathway, whereas the RIZ injection alone did not. In addition, overuse of RIZ, administration of an IS stimulus, and a combination of these treatments, decreased the periorbital withdrawal threshold, with IS-RIZ treatment having the most significant effects. Both chronic RIZ exposure and recurring nociception decreased 5-HT expression, whereas IS-RIZ treatment led to decreased expression of 5-HT and upregulation of 5-HT2AR, which was positively correlated with Fos activation. These findings suggest that overuse of RIZ does not directly induce pain via the activation of nociceptive pathways but may increase hyperalgesia by influencing the pain modulation system. Furthermore, decreased 5-HT levels and upregulation of 5-HT2AR may play important roles in this system. Taken together, these findings indicate that medication overuse and frequent headache attacks can promote the neural plasticity associated with MOH.

Associations Between Sleep Quality and Migraine Frequency: A Cross-Sectional Case-Control Study

Migraine has been associated with sleep disturbances. Relationship between sleep quality and migraine frequency is yet to be determined. The present study aimed to investigate sleep disturbances among low-frequency, moderate-frequency, high-frequency, and chronic migraineurs, with and without auras, with well-controlled confounding variables.This cross-sectional controlled study included 357 subjects from an outpatient headache clinic in Taiwan. Standardized questionnaires were utilized to collect demographic, migraine, sleep, depression, anxiety, and restless leg syndrome characteristics in all participants. According to frequency of migraine attacks, patients were divided into 4 groups: with 1 to 4 migraine days per month, 5 to 8 migraine days in a month, 9 to 14 migraine days in a month, and >14 migraine days per month. The Pittsburgh Sleep Quality Index (PSQI) and subgroup items were used to evaluate sleep quality. The association between migraine frequency and sleep quality was investigated using multivariable linear regression and logistic regression.The PSQI total score was highest in patients with high frequent migraine (10.0 ± 3.4) and lowest in controls (7.0 ± 3.4) with a significant trend analysis (P for trend = 0.006). Migraine frequency had an independent effect on the items "Cannot get to sleep within 30 minutes" (P < 0.001), "Wake up in the middle of the night or early morning" (P < 0.001), "Bad dreams" (P = 0.001), "Pain" (P = 0.004), and "Quality of sleep" (P < 0.001). The result showed the effect of migraine frequency in both the aura-present (P for trend = 0.008) and the aura-absent subgroups (P for trend = 0.011).High migraine frequency correlates with poor sleep quality and a higher prevalence of poor sleepers. These associations occur in migraine with aura and without aura.

Utilisation of prescription and over-the-counter triptans: a cross-sectional study in Stockholm, Sweden

PURPOSE

Triptans are widely used in acute migraine, and in some countries, they are also available over-the-counter (OTC). In Sweden, sales have increased for both prescription and OTC triptans. This study aimed to describe current prescribing and utilisation patterns of prescription and OTC triptans in Stockholm, Sweden.

METHODS

Register data from 4759 patients dispensed triptans in 2014 were used to study documented diagnosis of migraine, concomitant acute and preventive treatment for migraine, and contraindications. Survey data from 49 patients purchasing OTC triptans in three pharmacies were used to capture physician-diagnosed migraine, concomitant acute and preventive treatment for migraine, a behaviour of combining or alternating between prescription and OTC triptans, and pharmacy counselling rates.

RESULTS

Among the prescription triptan users, 52 % had a recorded diagnosis of migraine, 48 % had no other acute treatment, preventive treatment was rare (12 %) and contraindications were found in 2 % of the patients. Among the OTC triptan users, the majority (63 %) had been diagnosed by a physician and had a history of prescription triptan use, but combining or alternating between OTC and prescription triptans was rare. Concomitant acute treatment was reported in 53 % and preventive treatment was rare (4 %), despite high self-reported migraine frequencies. Some off-label use was detected, despite moderate to high counselling rates.

CONCLUSION

Triptans are prescribed with attention to safety but with poor recording of migraine diagnosis. OTC triptan users generally have a history of prescription triptan use. Preventive treatment rates are low in both groups. Strategies to discern patients who need other treatment options should be considered.

A review on the management of migraine in the Avicenna's Canon of Medicine

Migraine is a common type of headache which has a deep history dating back thousands of years. Avicenna (980-1032), a Persian scholar, made a great contribution to neurology including headache and migraine. The aim of this study is to consider Avicenna's description about migraine (Shaghighe in Persian language) including definition, etiology and intervention. Also, his definition and treatment approaches were considered based on current concepts and findings. Although Avicenna believed in humoral theory and divided migraine into two categories, hot and cold, and suggested special treatments for them as well as general considerations, most of his definitions and explained pathologies are supported by current concepts of medicine. He believed that the migraine can result from bone of skull and also intra-parenchymal; or from skull underneath membrane (dura-mater); or reaching substances from the painful side or from outer vein and arteries (extra cranial); or from brain and meninges (pia-mater). Furthermore, current findings show most medicinal plants mentioned by Avicenna for the treatment of migraine can have potentially significant effects such as remedies which stop central and peripheral sensitization [anti-neuroinflammatory agents, decreasing nitric oxide level, cyclooxygenase (COX)-2 inhibitors], as well as serotonergics, neuroprotective agents and analgesics.

Modulation of auditory brainstem responses by serotonin and specific serotonin receptors

The neuromodulator serotonin is found throughout the auditory system from the cochlea to the cortex. Although effects of serotonin have been reported at the level of single neurons in many brainstem nuclei, how these effects correspond to more integrated measures of auditory processing has not been well-explored. In the present study, we aimed to characterize the effects of serotonin on far-field auditory brainstem responses (ABR) across a wide range of stimulus frequencies and intensities. Using a mouse model, we investigated the consequences of systemic serotonin depletion, as well as the selective stimulation and suppression of the 5-HT1 and 5-HT2 receptors, on ABR latency and amplitude. Stimuli included tone pips spanning four octaves presented over a forty dB range. Depletion of serotonin reduced the ABR latencies in Wave II and later waves, suggesting that serotonergic effects occur as early as the cochlear nucleus. Further, agonists and antagonists of specific serotonergic receptors had different profiles of effects on ABR latencies and amplitudes across waves and frequencies, suggestive of distinct effects of these agents on auditory processing. Finally, most serotonergic effects were more pronounced at lower ABR frequencies, suggesting larger or more directional modulation of low-frequency processing. This is the first study to describe the effects of serotonin on ABR responses across a wide range of stimulus frequencies and amplitudes, and it presents an important step in understanding how serotonergic modulation of auditory brainstem processing may contribute to modulation of auditory perception.

Association Between Polymorphisms of DRD2, COMT, DBH, and MAO-A Genes and Migraine Susceptibility: A Meta-Analysis

Some epidemiological studies have investigated the relationship between genetic polymorphisms of DRD2, COMT, DBH, and MAO-A and migraine susceptibility, but the results are still inconsistent. Thus, our aim was to further assess the association through a meta-analysis.We examined 5 single nucleotide polymorphisms (SNPs) in 4 genes, including DRD2 rs1799732 and rs6275, DBH rs7239728, MAI-A-VNTR, and COMT rs4680, and performed a meta-analysis of 11 published case-control studies including 3138 cases and 4126 controls. Odd ratios (ORs) with 95% confidence intervals (95% CIs) were used to evaluate the association between the 5 genetic polymorphisms and migraine susceptibility.There was no significant relationship between migraine susceptibility and 4 genetic polymorphisms of DRD2 rs1799732 and rs6275, DBH rs7239728, and MAO-A-VNTR. Nevertheless, decreased risk of migraine was observed to be in association with COMT rs4680 polymorphism in overall analysis (AA vs. GG + GA: OR = 0.76, 95% CI = 0.60-0.97, PHet > 0.642, I = 0), and in Caucasian group after subgroup analysis (AA vs. GG + GA: OR = 0.75, 95% CI = 0.58-0.96, PHet > 0.433, I = 0).Studied polymorphisms of DRD2, DBH, and MAO-A genes may not be associated with migraine susceptibility. However, COMT rs4680 polymorphism may decrease the risk of migraine, especially in Caucasians. The failure to evaluate environmental influence and provide adjusted effect size estimates highlights the need for additional studies in a large number to take these factors into consideration, thus better elucidating the role of the genes tested in migraine.

ASICs as therapeutic targets for migraine

Migraine is the most common neurological disorder and one of the most common chronic pain conditions. Despite its prevalence, the pathophysiology leading to migraine is poorly understood and the identification of new therapeutic targets has been slow. Several processes are currently thought to contribute to migraine including altered activity in the hypothalamus, cortical-spreading depression (CSD), and afferent sensory input from the cranial meninges. Decreased extracellular pH and subsequent activation of acid-sensing ion channels (ASICs) may contribute to each of these processes and may thus play a role in migraine pathophysiology. Although few studies have directly examined a role of ASICs in migraine, studies directly examining a connection have generated promising results including efficacy of ASIC blockers in both preclinical migraine models and in human migraine patients. The purpose of this review is to discuss the pathophysiology thought to contribute to migraine and findings that implicate decreased pH and/or ASICs in these events, as well as propose issues to be resolved in future studies of ASICs and migraine. This article is part of the Special Issue entitled 'Acid-Sensing Ion Channels in the Nervous System'.

Abnormal inhibition-excitation imbalance in migraine

Background

People with migraine show increased surround suppression of perceived contrast, a perceptual analogue of centre-surround antagonistic interactions in visual cortex. A proposed mechanism is that cortical ‘hyperexcitability’ or ‘hyperresponsivity’, a prominent theory in the migraine literature, drives abnormal excitatory-inhibitory balance to give increased local inhibition. The purpose of this cross-sectional study was to determine whether cortical hyperresponsivity and excitatory-inhibitory imbalance manifests in the visual cortical response of migraine sufferers.

Methods

Interictal steady-state visual evoked potentials (VEPs) in response to 0 to 97% contrast were recorded in 30 migraine participants (15 without aura, 15 with aura) and 21 non-headache controls. Monotonicity indices were calculated to determine response saturation or supersaturation. Contrast gain was modelled with a modified saturating hyperbolic function to allow for variation in excitation and inhibition.

Results

A greater proportion of migraine participants (43%) than controls (14%) exhibited significant VEP supersaturation at high contrast, based on monotonicity index (chi-square, p = 0.028). Supersaturation was also evident by the trend for greater suppressive exponent values in migraine compared to control individuals (Mann-Whitney rank sum, p = 0.075).

Conclusions

Supersaturation in migraine is consistent with excess excitation (hyperresponsivity) driving increased network inhibition and provides support for excitatory-inhibitory imbalance as a pathophysiological disturbance in migraine.

Serotonin, 5HT1 agonists, and migraine: new data, but old questions still not answered

PURPOSE OF REVIEW

The serotonergic system has long been linked to migraine but recent studies highlight how much is still unclear about this link. And recent data add to the uncertainty of where/how triptans act and why they are headache specific.

RECENT FINDINGS

Markers of 5HT levels in the brains of migraine patients show no changes between attacks. Several recent meta-analyses show the most convincing data on genetic differences in the serotonergic system for 5HT transporters. Findings of additional triptan actions on peripheral trigeminovascular neurons and in the hypothalamus add more fuel to the debate on where these drugs act. A growing list of studies show efficacy of multiple triptans and other 5HT1b/1d agonists in preclinical models of nonheadache pain arguing for reevaluation of whether these drugs have efficacy in other pain states. Despite these issues, serotonergic drugs continue to be the gold standard for abortive agents with new members on the horizon (5HT1f agonists).

SUMMARY

Given the clear efficacy of serotonergic drugs for migraine, continued study on the role of the endogenous 5HT system may lead to more novel therapies. And with the list of studies demonstrating efficacy triptans in models of nonheadache, clinical studies should address whether these drugs work for other types of pain.

Psychiatric comorbidity of chronic daily headache: focus on traumatic experiences in childhood, post-traumatic stress disorder and suicidality

The fifth edition of the Diagnostic and Statistic Manual (DSM-5) reclassified some mental disorders recently. Post-traumatic stress disorder (PTSD) is in a new section termed "trauma- and stressor-related disorder". Community-based studies have shown that PTSD is associated with a notably high suicidal risk. In addition to previous findings of comorbidity between chronic daily headache (CDH) and both depressive disorders and anxiety disorders, recent data suggest that frequency of childhood maltreatment, PTSD, and suicidality are also increased in CDH. CDH patients with migraine aura are especially at risk of suicidal ideation. Research suggests that migraine attack, aura, frequency, and chronicity may all be related to serotonergic dysfunction. Vulnerability to PTSD and suicidality are also linked to brain serotonin function, including polymorphisms in the serotonin transporter gene (5-HTTLPR). In the present review, we focus on recent advances in knowledge of traumatic experiences in childhood, PTSD, and suicidality in relation to migraine and CDH. We hypothesize that vulnerability to PTSD is associated with migraine attack, migraine aura, and CDH. We further postulate that these associations may explain some of the elevated suicidal risks among patients with migraine, migraine aura, and/or CDH. Field studies are required to support these hypotheses.