The genetic basis of migraine: how much do we know?

Current Update on Categorization of Migraine Subtypes on the Basis of Genetic Variation: a Systematic Review

Migraine is a complex neurovascular disorder that is characterized by severe behavioral, sensory, visual, and/or auditory symptoms. It has been labeled as one of the ten most disabling medical illnesses in the world by the World Health Organization (Aagaard et al Sci Transl Med 6(237):237ra65, 2014). According to a recent report by the American Migraine Foundation (Shoulson et al Ann Neurol 25(3):252-9, 1989), around 148 million people in the world currently suffer from migraine. On the basis of presence of aura, migraine is classified into two major subtypes: migraine with aura (Aagaard et al Sci Transl Med 6(237):237ra65, 2014) and migraine without aura. (Aagaard K et al Sci Transl Med 6(237):237ra65, 2014) Many complex genetic mechanisms have been proposed in the pathophysiology of migraine but specific pathways associated with the different subtypes of migraine have not yet been explored. Various approaches including candidate gene association studies (CGAS) and genome-wide association studies (Fan et al Headache: J Head Face Pain 54(4):709-715, 2014). have identified the genetic markers associated with migraine and its subtypes. Several single nucleotide polymorphisms (Kaur et al Egyp J Neurol, Psychiatry Neurosurg 55(1):1-7, 2019) within genes involved in ion homeostasis, solute transport, synaptic transmission, cortical excitability, and vascular function have been associated with the disorder. Currently, the diagnosis of migraine is majorly behavioral with no focus on the genetic markers and thereby the therapeutic intervention specific to subtypes. Therefore, there is a need to explore genetic variants significantly associated with MA and MO as susceptibility markers in the diagnosis and targets for therapeutic interventions in the specific subtypes of migraine. Although the proper characterization of pathways based on different subtypes is yet to be studied, this review aims to make a first attempt to compile the information available on various genetic variants and the molecular mechanisms involved with the development of MA and MO. An attempt has also been made to suggest novel candidate genes based on their function to be explored by future research.

Prevalence and clinical features associated to bipolar disorder-migraine comorbidity: a systematic review

BACKGROUND

The prevalence and clinical features associated with bipolar disorders (BDs)-migraine comorbidity have been reported inconsistently across different studies, therefore warranting a systematic review on the matter.

METHODS

A systematic review was conducted in accordance with the PRISMA statement searching major electronic databases for documents indexed between January, 2000 and July, 2014. Eligible studies were those including quantitative data on prevalence rates and clinical features associated to BD-migraine comorbidity; case reports excluded. Three authors independently conducted searches, quality assessment of the studies and data extraction.

RESULTS

Several cross-sectional studies, and a handful of retrospective follow-up studies or non-systematic reviews assessed the prevalence and/or the clinical correlates of migraine-BD comorbidity. High prevalence rates and a significant burden of BD-migraine comorbidity were common findings, particularly in case of BD-II women (point-prevalence rates up to 77%), migraine with aura (up to 53%) and/or cyclothymic temperament (up to 45% of the cases).

LIMITATIONS

Some of the biases encountered in a few studies accounted by the present review may nonetheless have hampered the generalizability of the overall conclusions drawn herein.

CONCLUSIONS

BD-migraine comorbidity may comprise of a sub-phenotype of BDs requiring patient-tailored therapeutic interventions to achieve an optimal outcome. Specifically, additional studies including longitudinal follow-up studies are aimed in order to shed further light on the actual prevalence rates and clinical features associated to BD-migraine comorbidity, with a special emphasis towards the clinically suggestive potential connection between mixed features, bipolar depression, migraine, and increased risk for suicidality. PROSPERO registration number: CRD42014009335.

Olfactory Hallucinations without Clinical Motor Activity: A Comparison of Unirhinal with Birhinal Phantosmia

Olfactory hallucinations without subsequent myoclonic activity have not been well characterized or understood. Herein we describe, in a retrospective study, two major forms of olfactory hallucinations labeled phantosmias: one, unirhinal, the other, birhinal. To describe these disorders we performed several procedures to elucidate similarities and differences between these processes. From 1272, patients evaluated for taste and smell dysfunction at The Taste and Smell Clinic, Washington, DC with clinical history, neurological and otolaryngological examinations, evaluations of taste and smell function, EEG and neuroradiological studies 40 exhibited cyclic unirhinal phantosmia (CUP) usually without hyposmia whereas 88 exhibited non-cyclic birhinal phantosmia with associated symptomology (BPAS) with hyposmia. Patients with CUP developed phantosmia spontaneously or after laughing, coughing or shouting initially with spontaneous inhibition and subsequently with Valsalva maneuvers, sleep or nasal water inhalation; they had frequent EEG changes usually ipsilateral sharp waves. Patients with BPAS developed phantosmia secondary to several clinical events usually after hyposmia onset with few EEG changes; their phantosmia could not be initiated or inhibited by any physiological maneuver. CUP is uncommonly encountered and represents a newly defined clinical syndrome. BPAS is commonly encountered, has been observed previously but has not been clearly defined. Mechanisms responsible for phantosmia in each group were related to decreased gamma-aminobutyric acid (GABA) activity in specific brain regions. Treatment which activated brain GABA inhibited phantosmia in both groups.

Endothelial Nitric Oxide Synthase and Angiotensin Converting Enzyme Gene Polymorphisms in Migraine Patients

INTRODUCTION

In this study, we investigated the association of migraine with the Variable Number of Tandem Repeats (VNTR), repeated as 27 base pair, gene polymorphism in intron 4 of the endothelial nitric oxide synthase (eNOS) and the insertion/deletion of angiotensin converting enzyme (ACE) gene polymorphisms.

METHODS

One hundred and five migraine and ninety seven healthy female control subjects were enrolled in the study. The patients were subdivided as migraine with aura and without aura, and the frequency and severity of migraine headaches were recorded. The eNOS VNTR (eNOS 4 a/b) and ACE insertion/deletion gene polymorphisms (ACE I/D) were assessed by polymerase chain reactions.

RESULT

The allele and genotype frequencies of eNOS 4 a/b gene polymorphism showed no difference between the migraine and control groups. The genotypic distribution of the ACE I/D gene polymorphism in the migraine group significantly differed from that in the control group. The DD and ID genotype increased the risk of migraine as much as 2.571 (95% CI-1.138-5.811) and 4.453 (95% CI-2.006-9.883) compared to the II genotype. The same increased risk sustained for both genotypes in the migraine with aura subgroup, but only the ID genotype remained as the risk factor in the migraine without aura subgroup (OR-3.750, 95% CI-1.493-9.420). No association of gene polymorphisms with migraine frequency and severity was observed.

CONCLUSION

Our findings support the relationship between migraine and the ACE I/D gene polymorphism. However, no association was found between migraine and the eNOS 4 a/b gene polymorphism.

Spinocerebellar ataxia type 6

The autosomal dominant spinocerebellar ataxias (SCA) are a genetically heterogeneous group of neurodegenerative disorders characterized by progressive motor incoordination, in some cases with ataxia alone and in others in association with additional progressive neurological deficits. Spinocerebellar ataxia type 6 (SCA6) is the prototype of a pure cerebellar ataxia, associated with a severe form of progressive ataxia and cerebellar dysfunction. SCA6, originally classified as such by Zhuchenko et al. (1997), is caused by a CAG repeat expansion in the CACNA1A gene which encodes the α1A subunit of the P/Q-type voltage-gated calcium channel. SCA6 is one of ten polyglutamine-encoding CAG nucleotide repeat expansion disorders comprising other neurodegenerative disorders such as Huntington's disease. The present review describes clinical, genetic, and pathological manifestations associated with this illness. Currently, there is no treatment for this neurodegenerative disease. Successful therapeutic strategies must target a valid pathological mechanism; thus, understanding the underlying mechanisms of disease is crucial to finding a proper treatment. Hence, this chapter will discuss as well the molecular mechanisms possibly associated with SCA6 pathology and their implication for the development of future treatment.

Psychiatric comorbidity and suicide risk in patients with chronic migraine

The aim of this study was to explore the impact of mental illness among patients with migraine. We performed MedLine and PsycINFO searches from 1980 to 2008. Research has systematically documented a strong bidirectional association between migraine and psychiatric disorders. The relationship between migraine and psychopathology has often been clinically discussed rather than systematically studied. Future research should include sound methodologically-based studies focusing on the interplay of factors behind the relationship between migraine, suicide risk, and mental illness.

Endothelial nitric oxide synthase (Glu298Asp) polymorphism is an independent risk factor for migraine with aura

OBJECTIVE

The aim of the present study was to evaluate whether the functional endothelial nitric oxide synthase (eNOS) Glu298Asp polymorphism, which has been demonstrated to decrease the endothelial NOS activity, might be a risk factor for migraine.

BACKGROUND

It has widely demonstrated that nitric oxide (NO) is involved in migraine pathogenesis. Several genetic risk factors have been associated with migraine, but no study has unraveled a possible relationship between migraine and eNOS Glu298Asp. Methods.-One hundred fifty-six migraine patients and 125 healthy nonheadache volunteers entered the study. Demographic and clinical characteristics were carefully recorded, and a neurological workup was performed.

RESULTS

eNOS AspAsp homozygous patients had a 3-fold time risk for migraine with aura (MA) when compared to migraine without aura (MO) patients (OR-3.02, 95% CI-1.21 to 7.51), and more than 2-fold time increased risk when compared to control subjects (OR-2.21, 95% CI-1.00 to 5.04). In migraine patients, no difference in age at onset, mean attack's intensity, family history for any of the studied comorbidities, or the presence of comorbidities was found in eNOS AspAsp homozygous compared to eNOS GluGlu or eNOS GluAs carriers.

CONCLUSIONS

Homozygous Asp298, a common variant of the eNOS gene, is an independent risk factor for MA in this study population.

High anxiety and migraine are associated with the s allele of the 5HTTLPR gene polymorphism

The 5HTTLPR polymorphism of the serotonin transporter gene has been associated with anxiety disorders and also migraine, suggesting a common etiological background of these disorders. This association is further supported by the high comorbidity of these disorders. In our study Spielberger's State-Trait Anxiety Inventory and the 5HTTLPR genotype were investigated in a cohort of 97 psychiatrically healthy females also including 45 migraineurs. Higher state anxiety scores were significantly associated with the s allele either in the whole sample or when the group was separated into migraineurs and non-migraineurs. Migraineurs also had a significantly higher frequency of the s allele. Our results indicate that even in a healthy population the s allele is associated with a high anxiety endophenotype. The association of migraine with anxiety may be explained by the higher rate of individuals carrying the s allele among migraineurs.

Molecular basis of inherited calcium channelopathies: role of mutations in pore-forming subunits

The pore-forming alpha subunits of voltage-gated calcium channels contain the essential biophysical machinery that underlies calcium influx in response to cell depolarization. In combination with requisite auxiliary subunits, these pore subunits form calcium channel complexes that are pivotal to the physiology and pharmacology of diverse cells ranging from sperm to neurons. Not surprisingly, mutations in the pore subunits generate diverse pathologies, termed channelopathies, that range from failures in excitation-contraction coupling to night blindness. Over the last decade, major insights into the mechanisms of pathogenesis have been derived from animals showing spontaneous or induced mutations. In parallel, there has been considerable growth in our understanding of the workings of voltage-gated ion channels from a structure-function, regulation and cell biology perspective. Here we document our current understanding of the mutations underlying channelopathies involving the voltage-gated calcium channel alpha subunits in humans and other species.

Migraine with and without aura: association with depression and anxiety disorder in a population-based study. The HUNT Study

Some data indicate that migraine with aura (MA) is more strongly associated with anxiety disorder and depression than migraine without aura (MoA), but the evidence is not conclusive. In the Nord-Trøndelag Health study 1995-1997, a total of 49 205 (75% of the participants) subjects gave valid answers to both HADS (Hospital Anxiety and Depression Scale) and a validated headache questionnaire. Associations between anxiety disorder/depression and MA/MoA were evaluated by multiple logistic regression analysis. Depression (DEP) [odds ratio (OR) 1.7; 95% confidence interval (CI) 1.2, 2.6] and depression with comorbid anxiety disorder (COM) (OR 1.6; 95% CI 1.2, 2.1) were more likely in women having MA than in those with MoA. No stronger association was found for pure anxiety disorder (ANX) in MA vs. MoA (OR 0.9; 95% CI 0.7, 1.5). Among men, we found no difference in prevalence of depression and anxiety disorders between MA and MoA. This is a new finding that might have relevance for both research and clinical treatment.

Genetics of Migraine: An Update

Observations including the long-recognized tendency of migraine to run in families, the high concordance rates for migraine in twins reared together or apart, and the association of specific mutations with a rare migraine form are consistent with a genetic contribution to the disorder. This paper summarizes major findings to date on the genetics of migraine. Study of the heritability of migraine, particularly the common forms of migraine, is beset by several challenges including the absence of easily measurable biological markers, uncertainty about the etiologic and clinical overlap among migraine types, and the apparently complex interplay of environmental and genetic factors in determining migraine phenotype. Nevertheless, significant progress has been realized in recent years. Familial hemiplegic migraine, a rare migraine variant, appears to be transmitted by a Mendelian, autosomal dominant mode of inheritance involving mutations in at least 2 genes. These genes do not seem to be critically involved in the other forms of migraine; however, several other susceptibility loci for more common forms of migraine have been identified in recent genome-wide screens and candidate-locus studies. These and other data suggest that the genetic contribution to migraine is complex, multifactorial, and subject to significant modification by environmental factors.

The role of vascular and hormonal genes in migraine susceptibility

Migraine is a primary headache disorder that involves both genetic and environmental components. Migraine is considered to be a polygenic disorder with a number of susceptibility genes having a minor but nonetheless significant impact on susceptibility. Migraine candidate gene studies have concentrated mainly on genes involved in neurotransmitter pathways, however evidence also exists for a role for alterations in vascular and hormonal function in migraine susceptibility. We present here a mini-review of genetic studies, investigating the potential role of vascular and hormonal gene variants, and discuss how vascular and hormonal dysfunction may impact on migraine susceptibility. We propose that the potential role of vascular and hormonal genes in this disorder warrants further investigation.

Investigating the Association Between Notch3 Polymorphism and Migraine

OBJECTIVE

The aim of the present study was to evaluate whether the functional Notch3 polymorphism T6746C, which is not causative for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), might be a risk factor for migraine.

BACKGROUND

It has been recently demonstrated that migraine is characterized by subclinical brain infarctions and white matter lesions. Several genetic risk factors have been associated with migraine, but no study has unraveled a possible relationship between migraine and Notch3, which is involved in vascular damage. Mutations in Notch3 gene have been demonstrated to be pathogenetic for CADASIL, a small vessel disease of the brain characterized by migraine.

METHODS

A total of 156 migraine patients and 128 nonheadache healthy volunteers entered the study. Demographic and clinical characteristics were carefully recorded, and a neurological work-up was performed. Moreover, each subject underwent a blood sampling for Notch3 genotype determination.

RESULTS

Notch3 genotypes as well as allele frequencies did not differ in migraine patients compared to controls, even adjusting for the presence of possible confounds. No difference has been found either in migraine patients with aura or in those without aura.

CONCLUSIONS

These findings support the view that functional polymorphism T6746C in Notch3 gene is not involved in increasing the risk of migraine or migraine subtypes.

Is migraine in unipolar depressed patients a bipolar spectrum trait?

BACKGROUND

It is well known that affective disorders and migraine often coexist in the same patients, and some information is available indicating that migraine is particularly prevalent in bipolar II disorder. The aims of this study were to compare the clinical features in unipolar depressed patients with and without comorbid migraine to bipolar patients.

METHODS

Semi-structured interview of 201 patients with major affective disorders, using DSM-IV criteria for affective disorders combined with Akiskal's criteria for affective temperaments, and IHS-criteria for migraine.

RESULTS

Compared to the group of patients having unipolar depressions without comorbid migraine (n = 51) the group with unipolar depression and migraine (n = 63) had a higher number of depressive episodes (4.5 vs. 2.5, P = 0.017), significantly higher prevalences of affective temperaments (46% vs. 16%, P = 0.001), irritability (70% vs. 45%, P = 0.008), seasonal variation (22% vs. 5%, P = 0.017), agoraphobia (44% vs. 26%, P = 0.036), asthma (25% vs. 6%, P = 0.006) and migraine in family (59% vs. 29%, P = 0.002). The clinical features of unipolar depressed patients with comorbid migraine resemble the bipolar II patients (n = 51) in this sample.

LIMITATIONS

Non-blind, cross-sectional assessment.

CONCLUSIONS

These results indicate that there may be important clinical differences between unipolar depressed patients with and without comorbid migraine, possibly indicating that migraine in depressed patients is a bipolar spectrum trait.

Lack of interaction between a polymorphism in the dopamine D2 receptor gene and the clinical features of migraine

The purpose of this study was to evaluate whether a particular genotype of the dopamine D2 receptor (DRD2) gene would affect the clinical features of migraine. In a group of 118 migraineurs (55 migraine with aura and 63 migraine without aura patients), we tested the association of the biallelic C/T NcoI DRD2 polymorphism with several characteristics of the disease. Genotype and allele frequencies resulted similarly distributed in migraine with aura and migraine without aura patients (chi2 = 1.58, P = 0.45 and chi2 = 0.09, P = 0.77, respectively). The different DRD2 genotypes (C/C, C/T and T/T) had no significant effects on age at onset of migraine, presence of premonitory phenomena, frequency of headache attacks, associated symptoms, psychological features and quality of life of our migraine patients. The results of our study do not support a role for the DRD2 gene in modifying the clinical features of migraine.

The estrogen receptor 1 G594A polymorphism is associated with migraine susceptibility in two independent case/control groups

Migraine is a painful and debilitating disorder with a significant genetic component. Steroid hormones, in particular estrogen, have long been considered to play a role in migraine, as variations in hormone levels are associated with migraine onset in many sufferers of the disorder. Steroid hormones mediate their activity via hormone receptors, which have a wide tissue distribution. Estrogen receptors have been localized to the brain in regions considered to be involved in migraine pathogenesis. Hence it is possible that genetic variation in the estrogen receptor gene may play a role in migraine susceptibility. This study thus examined the estrogen receptor 1 (ESRalpha) gene for a potential role in migraine pathogenesis and susceptibility. A population-based cohort of 224 migraine sufferers and 224 matched controls were genotyped for the G594A polymorphism located in exon 8 of the ESR1 gene. Statistical analysis indicated a significant difference between migraineurs and non-migraineurs in both the allele frequencies (P=0.003) and genotype distributions (P=0.008) in this sample. An independent follow-up study was then undertaken using this marker in an additional population-based cohort of 260 migraine sufferers and 260 matched controls. This resulted in a significant association between the two groups with regard to allele frequencies (P=8 x 10(-6)) and genotype distributions (P=4 x 10(-5)). Our findings support the hypothesis that genetic variation in hormone receptors, in particular the ESR1 gene, may play a role in migraine.

Comparative study of anxiety, depression, somatization, functional disability, and illness attribution in adolescents with chronic fatigue or migraine

OBJECTIVE

To compare adolescents with migraine, unexplained profound chronic fatigue of >6 months duration, and normal school controls on measures of anxiety, depression, somatization, functional disability, and illness attribution.

METHODS

Adolescents referred to Children's Hospital and Regional Medical Center for behavioral treatment of migraine (n = 179) or evaluation of chronic fatigue (n = 97) were compared with a group of healthy controls of similar age and sex from a middle school (n = 32). Subjects completed the Spielberger State-Trait Anxiety Inventory-Trait Form, the Children's Depression Inventory, the Childhood Somatization Inventory, and estimated the number of school days missed in the past 6 months because of illness. Migraine and fatigued subjects completed an illness attribution questionnaire.

RESULTS

Subjects in the 3 groups were 56% to 70% female and ranged from 11 years old to 18 years old with a mean age of 14.0 +/- 2.0. Forty-six of the 97 chronically fatigued adolescents met 1994 Centers for Disease Control and Prevention (CDC) criteria for chronic fatigue syndrome (CDC-CFS), while 51 had idiopathic chronic fatigue syndrome (I-CFS) that did not meet full CDC criteria. Adolescents with migraine had significantly higher anxiety scores than those with I-CFS or controls and higher somatization scores than controls. Adolescents with CDC-CFS had significantly higher anxiety scores than those with I-CFS or controls, and higher depression and somatization scores than all other groups. There were significant differences between all groups for school days missed with CDC-CFS more than I-CFS more than migraine more than controls. Parents of adolescents with unexplained I-CFS had significantly lower attribution scores relating illness to possible psychological or stress factors than parents of adolescents with CDC-CFS or migraine.

CONCLUSIONS

Adolescents referred to an academic center for evaluation of unexplained chronic fatigue had greater rates of school absenteeism than adolescents with migraine or healthy controls. Those meeting CDC-CFS criteria had higher anxiety scores than controls and higher depression and somatization scores than migraineurs or controls. Parents of adolescents with I-CFS were less likely to endorse psychological factors as possibly contributing to their symptoms than parents of adolescents with CDC-CFS or migraine.

Absence of known familial hemiplegic migraine (FHM) mutations in the CACNA1A gene in patients with common migraine: implications for genetic testing

Mutations in the gene CACNA1A have been known to cause familial hemiplegic migraine (FHM); it has been suggested, based on indirect genetic studies, that this gene may also be involved in common forms of migraine. To obtain data from direct gene analysis to test this hypothesis, we investigated 143 patients with common migraine, irrespective of their family history, for the presence of mutations known to result in the FHM phenotype; the mutations V714A, R192Q, R583Q, T666M, V1457L, and 11811L were absent in our patient sample. Furthermore, exons 4, 16, 17, and 36 were completely screened by single-strand conformation polymorphism (SSCP), and no other, hitherto unknown, mutations were detected. Bearing in mind that, in particular, the T666M mutation contributes to a large proportion of FHM linked to chromosome 19, we conclude that common migraine is distinct from FHM in its molecular basis and, therefore, most likely also in its pathophysiology. The possibility, however, of the existence of allelic disorders, with mutations located in other regions of the CACNA1A gene, cannot be ruled out. Molecular testing, therefore, is at present not a feasible option for the diagnosis and classification of migraine.

The prevalence of migraine in patients with bipolar and unipolar affective disorders

There is a well-known association between migraine and affective disorders, but the information is sparse concerning the prevalence of migraine in subgroups of the affective disorders. The present study was undertaken to investigate the prevalence of migraine in unipolar depressive, bipolar I and bipolar II disorders. Patients with major affective disorders (n = 62), consecutively admitted to an open psychiatric ward, were examined with a semi-structured interview based on DSM-IV diagnostic criteria, combined with separate criteria for affective temperaments. Diagnosis of unipolar and bipolar I disorders followed the DSM-IV criteria, while bipolar II disorder encompassed patients with either discrete hypomanic episodes or a cyclothymic temperament. Migraine was diagnosed according to IHS-criteria. Symptoms of migraine were found to be common in these patients, both in those with unipolar depression (46% prevalence of migraine) and in those with bipolar disorders (44% prevalence). Among the bipolar patients there was, however, a striking difference between the two diagnostic subgroups, with a prevalence of 77% in the bipolar II group compared with 14% in the bipolar I group (P = 0.001). These results support the contention that bipolar I and II are biologically separate disorders and point to the possibility of using the association of bipolar II disorder with migraine to study both the pathophysiology and the genetics of this affective disorder.

Clinical characteristics of patients with major affective disorders and comorbid migraine

The present study was undertaken to examine the clinical characteristics of patients with major affective disorders and comorbid migraine. Patients (n = 102) with an index episode of either major depression or mania were interviewed with a semi-structured interview based partly on DSM-IV criteria and partly on Akiskal's criteria for affective temperaments. Compared to the patients without migraine (n = 49), the patients with comorbid migraine (n = 53) had a higher frequency of bipolar II disorder (43% vs. 10%), a lower frequency of bipolar I disorder (11% vs. 33%), an approximately equal frequency of unipolar depressive disorder (45% vs. 57%) and a higher frequency of affective temperaments (45% vs. 22%). The migraine patients also had a greater number of anxiety disorders (3.0 vs. 1.9) and a higher frequency of panic disorder and agoraphobia. Gender distribution, age, age at onset of first affective episode, number of previous episodes and symptoms during depressive episodes were similar in both groups. Based on these findings it is suggested that the presence of migraine may be used to delineate a distinct subgroup of the major affective disorders.

Denaturing high-performance liquid chromatography: A review

Denaturing high-performance liquid chromatography (DHPLC) compares two or more chromosomes as a mixture of denatured and reannealed PCR amplicons, revealing the presence of a mutation by the differential retention of homo- and heteroduplex DNA on reversed-phase chromatography supports under partial denaturation. Temperature determines sensitivity, and its optimum can be predicted by computation. Single-nucleotide substitutions, deletions, and insertions have been detected successfully by on-line UV or fluorescence monitoring within 2-3 minutes in unpurified amplicons as large as 1.5 Kb. Sensitivity and specificity of DHPLC consistently exceed 96%. These features and its low cost make DHPLC one of the most powerful tools for the re-sequencing of the human and other genomes. Aside from its application to the mutational analysis of candidate genes, DHPLC has proven instrumental in elucidating human evolution and in the mapping of genes. Employing completely denaturing conditions, the utility of DHPLC has been extended to the genotyping of known polymorphisms by utilizing the ability of poly(styrene-divinylbenzene) to resolve single-stranded DNA molecules of identical size that differ in a single base. Under completely denaturing conditions, it is thus possible to resolve all possible base substitutions with the single exception of C-->G transversions. Improvements in throughput became feasible with the recent introduction of monolithic poly(styrene-divinylbenzene) capillaries that lend themselves to the fabrication of arrays connected to a multi-color laser induced fluorescence scanner or a mass spectrometer.

NiCl2 and amiloride induce spreading depression in guinea pig hippocampal slices

Spreading depressions (SD) occur in association with ischaemia, epilepsy and migraine. Intracellular calcium oscillations have been suggested to be involved in the generation and propagation of SD. The present study was performed to study the mechanism of conditioning guinea pig hippocampal slices by the T-type calcium channel blockers NiCl2 and amiloride. SD-like fluctuations of DC potential were recorded by inserting microelectrodes into the CA1 and CA3 regions. The SD occurrence was significantly greater with 10 micromol/l NiCl2 as well as with 25 and 50 micromol/l amiloride than with other concentrations of these substances. The concentration response curve was inversely U-shaped with the maximum repetition rates of SDs being achieved at 10 micromol/l NiCl2 as well as at 25 and 50 micromol/l amiloride. SD occurrence could be completely blocked by the NMDA antagonist APV (10 micromol/l) in all cases. These data demonstrate that modulation of the Ca2+ dynamics conditioned guinea pig hippocampal slices and increased their susceptibility to generate SD.

Olfactory and trigeminal event-related potentials in migraine

BACKGROUND

Trigeminal/neuronal hyperexcitability and spreading depression activating the trigemino-vascular system are discussed in migraine-pathophysiology. This study investigated trigeminal and olfactory event-related potentials in migraineurs.

METHODS

Nasal chemosensitivity was assessed in 19 female migraineurs with or without aura > 72 h before or after an attack and in 19 healthy females employing event-related cortical potentials (ERPs) after specific trigeminal stimulation of nasal nociceptors with short pulses of CO2, and specific olfactory stimulation with H2S. Odour thresholds and odour identification performance were also tested.

RESULTS

Migraineurs exhibited greater responses to trigeminal stimulation, indicated by significantly larger ERP amplitudes N1. In contrast, olfactory ERP amplitudes P1N1 were significantly smaller in migraineurs. A leave-one-out classification procedure on the basis of these two parameters assigned 76.3% cases correctly. The olfactory ERP amplitude discriminated better between groups than trigeminal ERPs (71.1 vs. 68.4% correct classification).

CONCLUSIONS

Our data suggest trigeminal hyperexcitability in migraineurs. A general increase of nasal chemosensitivity is not supported because of smaller olfactory ERP amplitudes in migraineurs. Olfactory ERPs discriminate better than trigeminal ERPs between migraineurs and controls, emphasizing the significance of the olfactory system in migraine.