Migraine aura: new information on underlying mechanisms

l-Citrulline ameliorates cerebral blood flow during cortical spreading depression in rats: Involvement of nitric oxide- and prostanoids-mediated pathway

l-Citrulline is a potent precursor of l-arginine, and exerts beneficial effect on cardiovascular system via nitric oxide (NO) production. Migraine is one of the most popular neurovascular disorder, and imbalance of cerebral blood flow (CBF) observed in cortical spreading depression (CSD) contributes to the mechanism of migraine aura. Here, we investigated the effect of l-citrulline on cardiovascular changes to KCl-induced CSD. in rats. Intravenous injection of l-citrulline prevented the decrease in CBF, monitored by laser Doppler flowmetry, without affecting mean arterial pressure and heart rate during CSD. Moreover, l-citrulline attenuated propagation velocity of CSD induced by KCl. The effect of l-citrulline on CBF change was prevented by l-NAME, an inhibitor of NO synthase, but not by indomethacin, an inhibitor of cyclooxygenase. On the other hand, attenuation effect of l-citrulline on CSD propagation velocity was prevented not only by l-NAME but also by indomethacin. In addition, propagation velocity of CSD was attenuated by intravenous injection of NOR3, a NO donor, which was diminished by ODQ, an inhibitor of soluble guanylyl cyclase. These results suggest that NO/cyclic GMP- and prostanoids-mediated pathway differently contribute to the effect of l-citrulline on the maintenance of CBF.

Nonpharmacological Interventions in Targeting Pain-Related Brain Plasticity

Chronic pain is a highly prevalent and debilitating condition that is frequently associated with multiple comorbid psychiatric conditions and functional, biochemical, and anatomical alterations in various brain centers. Due to its widespread and diverse manifestations, chronic pain is often resistant to classical pharmacological treatment paradigms, prompting the search for alternative treatment approaches that are safe and efficacious. The current review will focus on the following themes: attentional and cognitive interventions, the role of global environmental factors, and the effects of exercise and physical rehabilitation in both chronic pain patients and preclinical pain models. The manuscript will discuss not only the analgesic efficacy of these therapies, but also their ability to reverse pain-related brain neuroplasticity. Finally, we will discuss the potential mechanisms of action for each of the interventions.

Migraine: New Molecular Mechanisms

Migraine is an episodic headache disorder affecting more than 10% of the general population. Migraine arises from a primary brain dysfunction that leads to activation and sensitization of the trigeminovascular system. A major incompletely understood issue in the neurobiology of migraine concerns the molecular and cellular mechanisms that underlie the primary brain dysfunction and lead to activation and sensitization of the trigeminovascular system, thus generating and maintaining migraine pain. Here the author reviews recent discoveries that have advanced our understanding of these mechanisms toward a unifying pathophysiological hypothesis, in which cortical spreading depression (CSD), the phenomenon underlying migraine aura, assumes a key role. In particular, the author discusses the main recent findings in the genetics and neurobiology of familial hemiplegic migraine and the insights they provide into the molecular and cellular mechanisms that may lead to the increased susceptibility of CSD in migraineurs.

Clinical importance of the middle meningeal artery: A review of the literature

The middle meningeal artery (MMA) is a very important artery in neurosurgery. Many diseases, including dural arteriovenous fistula (DAVF), pseudoaneurysm, true aneurysm, traumatic arteriovenous fistula (AVF), moyamoya disease (MMD), recurrent chronic subdural hematoma (CSDH), migraine and meningioma, can involve the MMA. In these diseases, the lesions occur in either the MMA itself and treatment is necessary, or the MMA is used as the pathway to treat the lesions; therefore, the MMA is very important to the development and treatment of a variety of neurosurgical diseases. However, no systematic review describing the importance of MMA has been published. In this study, we used the PUBMED database to perform a review of the literature on the MMA to increase our understanding of its role in neurosurgery. After performing this review, we found that the MMA was commonly used to access DAVFs and meningiomas. Pseudoaneurysms and true aneurysms in the MMA can be effectively treated via endovascular or surgical removal. In MMD, the MMA plays a very important role in the development of collateral circulation and indirect revascularization. For recurrent CDSHs, after burr hole irrigation and drainage have failed, MMA embolization may be attempted. The MMA can also contribute to the occurrence and treatment of migraines. Because the ophthalmic artery can ectopically originate from the MMA, caution must be taken to avoid causing damage to the MMA during operations.

Novel cytogenic and neurovascular niches due to blood-brain barrier compromise in the chronic pain brain

BACKGROUND

The mechanisms by which painful injuries are linked to the multitude of pain-related comorbidities and neuroplastic changes in the brain remain poorly understood. Here we propose a model that relies on epi-neuronal communication through the vascular system to effect various brain structures. Specifically, we hypothesize that the differential vulnerability of the blood-brain barrier (BBB) in different brain regions is associated with region-specific neuroplastic and neurovascular changes that are in turn associated with particular pain-related comorbidities.

PRESENTATION OF THE HYPOTHESIS

We will present our hypothesis by focusing on two main points: (A) chronic pain (CP) is associated with differential BBB compromise. (B) Circulating mediators leaking through the BBB create cytogenic and neovascular niches associated with pain-related co-morbidities.

TESTING THE HYPOTHESIS

Pre-clinically, our hypothesis can be tested by observing, in parallel, BBB compromise, (neo)vascularization, neurogenesis, and their co-localization in animal pain models using imaging, microscopy, biochemical and other tools. Furthermore, the BBB can be experimentally damaged in specific brain regions, and the consequences of those lesions studied on nociception and associated comorbidities. Recently developed imaging techniques allow the analysis of blood brain barrier integrity in patients providing a route for translation of the laboratory findings. Though perhaps more limited, post-mortem examination of brains with available pain histories constitutes a second approach to addressing this hypothesis.

IMPLICATIONS OF THE HYPOTHESIS

Understanding changes in BBB permeability in chronic pain conditions has clear implications both for understanding the pathogenesis of chronic pain and for the design of novel treatments to prevent chronic pain and its consequences. More broadly, this hypothesis may help us to understand how peripheral injuries impact the brain via mechanisms other than commonly studied efferent sensory pathways.

Familial hemiplegic migraine type-1 mutated cav2.1 calcium channels alter inhibitory and excitatory synaptic transmission in the lateral superior olive of mice

CaV2.1 Ca(2+) channels play a key role in triggering neurotransmitter release and mediating synaptic transmission. Familial hemiplegic migraine type-1 (FHM-1) is caused by missense mutations in the CACNA1A gene that encodes the α1A pore-forming subunit of CaV2.1 Ca(2+) channels. We used knock-in (KI) transgenic mice harbouring the pathogenic FHM-1 mutation R192Q to study inhibitory and excitatory neurotransmission in the principle neurons of the lateral superior olive (LSO) in the auditory brainstem. We tested if the R192Q FHM-1 mutation differentially affects excitatory and inhibitory synaptic transmission, disturbing the normal balance between excitation and inhibition in this nucleus. Whole cell patch-clamp was used to measure neurotransmitter elicited excitatory (EPSCs) and inhibitory (IPSCs) postsynaptic currents in wild-type (WT) and R192Q KI mice. Our results showed that the FHM-1 mutation in CaV2.1 channels has multiple effects. Evoked EPSC amplitudes were smaller whereas evoked and miniature IPSC amplitudes were larger in R192Q KI compared to WT mice. In addition, in R192Q KI mice, the release probability was enhanced compared to WT, at both inhibitory (0.53 ± 0.02 vs. 0.44 ± 0.01, P = 2.10(-5), Student's t-test) and excitatory synapses (0.60 ± 0.03 vs. 0.45 ± 0.02, P = 4 10(-6), Student's t-test). Vesicle pool size was diminished in R192Q KI mice compared to WT mice (68 ± 6 vs 91 ± 7, P = 0.008, inhibitory; 104 ± 13 vs 335 ± 30, P = 10(-6), excitatory, Student's t-test). R192Q KI mice present enhanced short-term plasticity. Repetitive stimulation of the afferent axons caused short-term depression (STD) of E/IPSCs that recovered significantly faster in R192Q KI mice compared to WT. This supports the hypothesis of a gain-of-function of the CaV2.1 channels in R192Q KI mice, which alters the balance of excitatory/inhibitory inputs and could also have implications in the altered cortical excitability responsible for FHM pathology.

Functions of the CB1 and CB 2 receptors in neuroprotection at the level of the blood-brain barrier

The cannabinoid (CB) receptors are the main targets of the cannabinoids, which include plant cannabinoids, endocannabinoids and synthetic cannabinoids. Over the last few years, accumulated evidence has suggested a role of the CB receptors in neuroprotection. The blood-brain barrier (BBB) is an important brain structure that is essential for neuroprotection. A link between the CB receptors and the BBB is thus likely, but this possible connection has only recently gained attention. Cannabinoids and the BBB share the same mechanisms of neuroprotection and both protect against excitotoxicity (CB1), cell death (CB1), inflammation (CB2) and oxidative stress (possibly CB independent)-all processes that also damage the BBB. Several examples of CB-mediated protection of the BBB have been found, such as inhibition of leukocyte influx and induction of amyloid beta efflux across the BBB. Moreover, the CB receptors were shown to improve BBB integrity, particularly by restoring the tightness of the tight junctions. This review demonstrated that both CB receptors are able to restore the BBB and neuroprotection, but much uncertainty about the underlying signaling cascades still exists and further investigation is needed.

Interactions of oxidative stress and neurovascular inflammation in the pathogenesis of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death in the young age group and leads to persisting neurological impairment in many of its victims. It may result in permanent functional deficits because of both primary and secondary damages. This review addresses the role of oxidative stress in TBI-mediated secondary damages by affecting the function of the vascular unit, changes in blood-brain barrier (BBB) permeability, posttraumatic edema formation, and modulation of various pathophysiological factors such as inflammatory factors and enzymes associated with trauma. Oxidative stress plays a major role in many pathophysiologic changes that occur after TBI. In fact, oxidative stress occurs when there is an impairment or inability to balance antioxidant production with reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels. ROS directly downregulate proteins of tight junctions and indirectly activate matrix metalloproteinases (MMPs) that contribute to open the BBB. Loosening of the vasculature and perivascular unit by oxidative stress-induced activation of MMPs and fluid channel aquaporins promotes vascular or cellular fluid edema, enhances leakiness of the BBB, and leads to progression of neuroinflammation. Likewise, oxidative stress activates directly the inflammatory cytokines and growth factors such as IL-1β, tumor necrosis factor-α (TNF-α), and transforming growth factor-beta (TGF-β) or indirectly by activating MMPs. In another pathway, oxidative stress-induced degradation of endothelial vascular endothelial growth factor receptor-2 (VEGFR-2) by MMPs leads to a subsequent elevation of cellular/serum VEGF level. The decrease in VEGFR-2 with a subsequent increase in VEGF-A level leads to apoptosis and neuroinflammation via the activation of caspase-1/3 and IL-1β release.

Development, maintenance and disruption of the blood-brain barrier

The interface between the blood circulation and the neural tissue features unique characteristics that are encompassed by the term 'blood-brain barrier' (BBB). The main functions of this barrier, namely maintenance of brain homeostasis, regulation of influx and efflux transport, and protection from harm, are determined by its specialized multicellular structure. Every constituent cell type makes an indispensable contribution to the BBB's integrity. But if one member of the BBB fails, and as a result the barrier breaks down, there can be dramatic consequences and neuroinflammation and neurodegeneration can occur. In this Review, we highlight recently gained mechanistic insights into the development and maintenance of the BBB. We then discuss how BBB disruption can cause or contribute to neurological disease. Finally, we examine how this knowledge can be used to explore new possibilities for BBB repair.

Diagnostics to look beyond the normal appearing brain tissue (NABT)? A neuroimaging study of patients with primary headache and NABT using magnetization transfer imaging and diffusion magnetic resonance

OBJECTIVE

Novel diagnostics can allow us to "look beyond" normal-appearing brain tissue (NABT) to unravel subtle alterations pertinent to the pathophysiology of primary headache, one of the most common complaints of patients who present to their physician across the medical specialties. Using both magnetization transfer imaging (MTI) and diffusion weighted imaging (DWI), we assessed the putative microstructural changes in patients with primary headache who display the NABT on conventional magnetic resonance imaging (conventional MRI).

METHODS

Subjects were 53 consecutive patients with primary headache disorders (40 = migraine with aura; 9 = tension headache; 4 = cluster headache) and 20 sex- and age-matched healthy volunteers. All subjects underwent evaluation with MRI, MTI, and DWI in order to measure the magnetization transfer ratio (MTR) and the apparent diffusion coefficient (ADC), respectively, in eight and six different regions of interest (ROIs).

RESULTS

Compared to healthy controls, we found a significant 4.3 % increase in the average ADC value of the occipital white matter in the full sample of patients (p = 0.035) and in patients with migraine (p = 0.046). MTR values did not differ significantly in ROIs between patients and healthy controls (p > 0.05).

CONCLUSIONS

The present study lends evidence, for the first time to the best of our knowledge, for a statistically significant microstructural change in the occipital lobes, as measured by ADC, in patients with primary headache who exhibit a NABT on MRI. Importantly, future longitudinal mechanistic clinical studies of primary headache (e.g., vis-à-vis neuroimaging biomarkers) would be well served by characterizing, via DWI, occipital white matter microstructural changes to decipher their broader biological significance.

Genetics of migraine in the age of genome-wide association studies

Genetic factors importantly contribute to migraine. However, unlike for rare monogenic forms of migraine, approaches to identify genes for common forms of migraine have been of limited success. Candidate gene association studies were often negative and positive results were often not replicated or replication failed. Further, the significance of positive results from linkage studies remains unclear owing to the inability to pinpoint the genes under the peaks that may be involved in migraine. Problems hampering these studies include limited sample sizes, methods of migraine ascertainment, and the heterogeneous clinical phenotype. Three genome-wide association studies are available now and have successfully identified four new genetic variants associated with migraine. One new variant (rs1835740) modulates glutamate homeostasis, thus integrates well with current concepts of neurotransmitter disturbances. This variant may be more specific for severe forms of migraine such as migraine with aura than migraine without aura. Another variant (rs11172113) implicates the lipoprotein receptor LRP1, which may interact with neuronal glutamate receptors, thus also providing a link to the glutamate pathway. In contrast, rs10166942 is in close proximity to TRPM8, which codes for a cold and pain sensor. For the first time this links a gene explicitly implicated in pain related pathways to migraine. The potential function of the fourth variant rs2651899 (PRDM16) in migraine is unclear. All these variants only confer a small to moderate change in risk for migraine, which concurs with migraine being a heterogeneous disorder. Ongoing large international collaborations will likely identify additional gene variants for migraine.

Increased matrix metalloproteinase activity is associated with migraine and migraine-related metabolic dysfunctions

OBJECTIVE

Matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) are discussed to be involved in the pathophysiology of migraine. Moreover, MMPs may also be involved in migraine-related metabolic alterations like an atherogenic lipid profile and hyperinsulinemia. The aim of this study was to investigate the impact of MMPs and TIMPs on migraine with and without aura and related metabolic dysfunctions.

METHODS

MMP activity, six MMPs and three TIMPs, parameters of the insulin and lipid metabolism as well as anthropometric parameters were determined in 124 non-obese subjects.

RESULTS

We found highly significant increased MMP activity in migraine patients independent of aura symptoms, which was associated with migraine with an odds ratio of 7.57. Interestingly, none of the determined MMPs and TIMPs showed significant different serum levels between migraine patients and healthy controls. We found significant correlations between MMP activity and parameters of the insulin and lipid metabolism, like Homeostasis Model Assessment index (HOMA index), cholesterol, triglycerides, and oxidized LDL.

CONCLUSION

We show here that increased MMP activity is tightly associated with migraine and migraine-related hyperinsulinemia and atherogenic lipid alterations. Our findings represent a new pathophysiological mechanism, which may be of clinical relevance, especially in regard to therapeutic approaches using MMP inhibitors.

Headache in thrombotic thrombocytopenic purpura: two cases with pathophysiological considerations

Headache is one of the most common neurological symptoms reported by patients with thrombotic thrombocytopenic purpura (TTP). Reports of headache characteristics in patients with TTP are rare. We report 2 cases of headache in a setting of TTP and review previous reports. Headache in TTP can have features in common with both migraine and tension-type headache. Although the pathophysiology of headache in TTP is not certain, platelet aggregation and activation may play a key role.

Migraine and patent foramen ovale: state of the science

Migraine is a prominent cause of recurrent pain, affecting 12% of the population. In several case series, approximately 50% of migraineurs with aura were found to have patent foramen ovale (PFO). The pathophysiological mechanism is speculated to be passage of microemboli and vasoactive chemicals through the PFO, thereby evading pulmonary filtration and triggering migraine symptoms. This article presents the results of retrospective and prospective research studies documenting the effects of PFO closure on migraine symptoms and presents emerging theories on possible pathologic mechanisms that may partially explain the increased risk of ischemic stroke in the migraine population. Finally, evidence-based recommendations are presented for health care providers for managing patients who have migraine and PFO.

Transient swelling, acidification, and mitochondrial depolarization occurs in neurons but not astrocytes during spreading depression

Cortical spreading depression (SD) is a propagating wave of neuronal and glial depolarization that manifests in several brain disorders. However, the relative contribution of neurons and astrocytes to SD genesis has remained controversial. This is in part due to a lack of utilizing sophisticated experimental methodologies simultaneously to quantify multiple cellular parameters. To address this, we used simultaneous two-photon imaging, intrinsic optical imaging, and electrophysiological recordings to ascertain the changes in cellular processes that are fundamental to both cell types including cell volume, pH, and metabolism during SD propagation. We found that SD was correlated in neurons with robust yet transient increased volume, intracellular acidification, and mitochondrial depolarization. Our data indicated that a propagating large conductance during SD generated neuronal depolarization, which led to both calcium influx triggering metabolic changes and H(+) entry. Notably, astrocytes did not exhibit changes in cell volume, pH, or mitochondrial membrane potentials associated with SD, but they did show alterations induced by changing external [K(+)]. This suggests that astrocytes are not the primary contributor to SD propagation but are instead activated passively by extracellular potassium accumulation. These data support the hypothesis that neurons are the crucial cell type contributing to the pathophysiological responses of SD.

[What is migraine?]

Migraine is a multifactorial and heterogeneous disorder. Diagnostic criteria have been established by the International Headache Society, however these are only supportive in terms of definition. The pathophysiology involves neuronal and vascular phenomena. The former is supported by the cortical spreading depression being the aura correlate and by brainstem and hypothalamic activation during the pain phase; the latter is suggested by the association between migraine and cardiovascular disease and findings of pathological vasoreactivity and endothelial dysfunction. Triptans and calcitonin gene-related peptide receptor antagonists show only a relative migraine-specific action; up to 30% of patients are nonresponders. Despite a clear genetic component, the discovery of specific genes for common forms of migraine remains elusive. Electrophysiological studies consistently indicate a characteristic "dyshabituation" concurring with clinical features of altered sensory perception. The age- and sex-specific pattern along with the effect of external factors on the course of migraine argue in favor of the involvement of epigenetic mechanisms. Knowledge about migraine is still limited, which hampers a definition.

Prophylactic drugs and cytokine and leptin levels in children with migraine

The study objective was to evaluate levels of the cytokines tumor necrosis factor alpha, interleukin-1beta, and interleukin-6 and of leptin, and then to determine the relationship between these levels and clinical responses in children with migraine after prophylactic therapy with one of four drugs. In all, 77 children who needed prophylactic drugs were treated with cyproheptadine, amitriptyline, propranolol, or flunarizine. Serum levels of the cytokines and leptin were measured before and 4 months after the treatment. Results were compared by drug for headache frequency, severity, and duration, the PedMIDAS score, and levels of each cytokine and of leptin. Each of the four drugs not only decreased the frequency and duration but also the severity of headache, and the PedMIDAS score. None of the drugs was found to be superior to others in terms of reduction in cytokine levels (P > 0.05). Both cyproheptadine and flunarizine (but not amitriptyline and propranolol) caused an increase in leptin levels (P < 0.05). These data suggest that cytokine levels are related to clinical responses, and might help in objective evaluation of clinical response in migraine. To our knowledge, the present study is the first trial to compare the effects of prophylactic drugs, cytokine levels, and leptin levels in children with migraine.

Migraine: an endemic disease inside the blood–brain barrier

Migraine is a complex neurological disorder that in recent years has received more and more attention. Knowledge regarding this primary headache has increased substantially, both with respect to its pathogenesis and how to effectively treat its symptoms. Over the years, the proposed location of the onset of migraine has moved from the periphery of the nervous system toward deeper parts of the brain. Migraine can be viewed as an inherited failure of trigeminal sensory processing with abnormal neuronal excitability in the trigeminal nucleus caudalis, which, in turn, causes central sensitization and amplification of the pain. Increased activation of the trigeminal nerve during a migraine attack causes release of the calcitonin gene-related peptide (CGRP) inside and outside the BBB. Within the CNS, CGRP promotes trigeminal sensory input and facilitates central sensitization. The future introduction of CGRP antagonists in clinical practice could represent significant progress for acute migraine therapy.

Spreading depression in the brainstem of the adult rat: electrophysiological parameters and influences on regional brainstem blood flow

Cortical spreading depression is a pathophysiological excitation wave that occurs during pathophysiological brain conditions such as ischemic brain infarction, migraine aura, and others. Judged from experiments in rodents, the brainstem is thought to be comparatively resistant to the generation of spreading depression. However, because spreading depression can be elicited in the brainstem of rat pups after superfusing the brainstem with solutions enhancing excitability, we reinvestigated spreading depression in the brainstem of the adult rat. Based on theoretical predictions indicating a major role of extracellular potassium in susceptibility to spreading depression, we used conditioning solutions in which chloride ions were replaced by acetate and tetraethylammonium chloride and a small amount of KCl were added. Under these conditions, spreading depression was reproducibly elicited in the brainstem either by topical application of KCl crystals to the brainstem surface or by local microinjection of KCl into the brainstem. The direct current shifts so elicited were accompanied by typical elevation of extracellular potassium ions, propagated in the brainstem, and were prevented by MK-801, an N-methyl D-aspartate blocker. During spreading depression, the regional blood flow in the brainstem was transiently increased. In addition, systemic arterial blood pressure, but not the heart rate, was transiently enhanced. In the nonconditioned brainstem, KCl stimulation neither elicited spreading depression nor induced changes in regional blood flow and blood pressure. These data show that proper conditioning renders the brainstem susceptible to spreading depression, and that spreading depression at this site elicits changes in local circulation and systemic blood pressure.

Neuron-glial interactions in blood-brain barrier formation

The blood brain barrier (BBB) evolved to preserve the microenvironment of the highly excitable neuronal cells to allow for action potential generation and propagation. Intricate molecular interactions between two main cell types, the neurons and the glial cells, form the underlying basis of the critical functioning of the nervous system across species. In invertebrates, interactions between neurons and glial cells are central in establishing a functional BBB. However, in vertebrates, the BBB formation and function is coordinated by interactions between neurons, glial cells, and endothelial cells. Here we review the neuron-glial interaction-based blood barriers in invertebrates and vertebrates and provide an evolutionary perspective as to how a glial-barrier system in invertebrates evolved into an endothelial barrier system. We also summarize the clinical relevance of the BBB as this protective barrier becomes disadvantageous in the pharmacological treatment of various neurological disorders.

The minicolumnopathy of autism: A link between migraine and gastrointestinal symptoms

Gastrointestinal symptoms are common medical problems among autistic patients. A leaky gut and viruses have been proposed as possible culprits but evidence for these etiological agents remains elusive. In this article, we put forward an alternate etiology: abdominal migraines. Recent postmortem studies in autism indicate the presence of a minicolumnopathy and its relationship to both serotonergic abnormalities and a hyperexcitable cortex. These features of phenomenology are also observed in miganeurs. A putative relationship between autism and migraine is further suggested by similarities in clinical histories and laboratory evidence. Some commonalities include the presence of neuroinflammation, sensory overstimulation (e.g., flickering of fluorescent lights), "food allergies", benefits from similar diets, and the role of nitric oxide. Abdominal migraine therefore stands as a falsifiable hypothesis with added importance accrued to potential therapeutic interventions.

Measurements of common iliac arterial blood flow in anurans using Doppler ultrasound

Color Doppler ultrasonography was used to determine time-average mean velocity and cross-sectional area of the common iliac artery in bullfrogs (Rana catesbeiana) and marine toads (Bufo marinus). Volumetric blood flow and weight-adjusted blood flow measurements were calculated from this data. Volumetric flow rates of frogs (31.8 ml/min) and toads (23.6 ml/min) did not differ statistically. However, when flow rates were adjusted for body mass, toads displayed a significantly greater flow rate of 238.1 ml/min/kg compared to 114.4 ml/min/kg for frogs.

Oxidative stress activates protein tyrosine kinase and matrix metalloproteinases leading to blood-brain barrier dysfunction

The blood-brain barrier (BBB) formed by brain microvascular endothelial cells (BMVEC) regulates the passage of molecules and leukocytes in and out of the brain. Oxidative stress is a major underlying cause of neurodegenerative and neuroinflammatory disorders and BBB injury associated with them. Using human BMVEC grown on porous membranes covered with basement membrane (BM) matrix (BBB models), we demonstrated that reactive oxygen species (ROS) augmented permeability and monocyte migration across BBB. ROS activated matrix metalloproteinases (MMP-1, -2, and -9) and decreased tissue inhibitors of MMPs (TIMP-1 and -2) in a protein tyrosine kinase (PTK)-dependent manner. Increase in MMPs and PTK activities paralleled degradation of BM protein and enhanced tyrosine phosphorylation of tight junction (TJ) protein. These effects and enhanced permeability/monocyte migration were prevented by inhibitors of MMPs, PTKs, or antioxidant suggesting that oxidative stress caused BBB injury via degradation of BM protein by activated MMPs and by PTK-mediated TJ protein phosphorylation. These findings point to new therapeutic interventions ameliorating BBB dysfunction in neurological disorders such as stroke or neuroinflammation.

Differential activation of extracellular signal-regulated kinase 1 and a related complex in neuronal nuclei

The extracellular signal-regulated kinases 1 and 2 (ERKs 1/2) are known to participate in regulating transcription in response to moderate depolarization, such as synaptic stimulation, but how the same active enzyme can differentially regulate distinct transcriptional programs induced with abnormal depolarization (high potassium) is unknown. We hypothesized that ERK1 or 2 accomplishes this differential nuclear response through close association with other proteins in stable complexes. In support of this hypothesis, we have found that immunoreactivity for an apparent high molecular weight complex containing phospho-ERK1 increased in response to synaptic stimulation, but decreased in response to high potassium; p-ERK immunoreactivity at 44/42 kDa increased in both cases. Evidence supporting the conclusion that the band of interest contained ERK1 in a complex, as opposed to it being an unrelated protein crossreacting with antibodies against p-ERK, is that ERK1 (p44 MAPK) and 14-3-3 protein were electroeluted from the 160-kDa band cut from a gel. We also found the nuclear complexes to be exceptionally durable, suggesting a role for the crosslinking enzyme, transglutaminase, in its stabilization. In addition, we found other components of the ERK pathway, including MEK, ERK2, p90RSK, and Elk-1, migrating at higher-than-expected weights in brain nuclei. These results describe a novel stable complex of ERK1 in neuronal nuclei that responds differentially to synaptic and depolarizing stimulation, and thus may be capable of mediating gene transcription in a way distinct from the monomeric protein.

The mycotoxins citrinin and gliotoxin differentially affect production of the pro-inflammatory cytokines tumour necrosis factor-alpha and interleukin-6, and the anti-inflammatory cytokine interleukin-10

BACKGROUND

Microbial growth is considered one of the major causes of indoor air problems. Moulds have been associated with asthma, allergy and a wide range of diffuse indoor air-related symptoms. However, mechanisms of the adverse health effects are not well understood.

OBJECTIVE

We hypothesized that the mycotoxins citrinin and gliotoxin could cause an imbalance between the secretion of the pro-inflammatory cytokines TNF-alpha and IL-6 and the anti-inflammatory cytokine IL-10.

METHODS

We investigated the influence of citrinin and gliotoxin on the human monocytic cell line Mono-Mac-6 (MM6) with and without lipopolysaccharide -stimulation. The levels of IL-10, IL-6 and TNF-alpha were analysed in cell culture supernatants by ELISA. Cell viability and cell apoptosis were measured by flow cytometry.

RESULTS

The strongest inhibition of cytokine secretion was found for IL-10. IL-6 levels were found to decrease in a dose-dependent manner along with reduced cell viability. TNF-alpha levels increased with low gliotoxin exposure (less than 100 ng/mL), but decreased significantly at 375 ng/mL and higher along with increased cell apoptosis and reduced cell viability. TNF-alpha levels were not reduced by citrinin exposure.

CONCLUSION

We observed a cytokine imbalance with a more pronounced reduction of IL-10 concentrations compared with those of TNF-alpha and IL-6. We suggest that low exposure doses of citrinin and gliotoxin (corresponding to less than 100 ng/mL gliotoxin and less than 10 mug/mL citrinin) may inhibit IL-10 and lead to increased risk of an inflammatory response with relative overproduction of TNF-alpha and IL-6. The findings and their clinical implications must be verified by human studies. However, we speculate that the observed biological effects may be of importance as they may partly explain the occurrence of diffuse general indoor air-related symptoms as well as the worsening of asthmatic inflammatory reactions experienced in mouldy environments.

Migraine: a review and future directions for treatment

Migraine is a chronic, neurological disorder generally manifesting itself in attacks with severe headache, nausea and an increased reactivity to sensory stimuli. A low migraine threshold is set by genetic factors, although the phenotype also modulates the manifestations. The 1-year prevalence is approximately 13% and is higher among women. Patients usually experience neuropsychological dysfunction, and sometimes also reversible focal neurological symptoms. The trajectories of the characteristic symptoms of acute migraine usually follow a similar time course, indicating a reciprocal underlying mechanism. A central nervous system hyperexcitability has been demonstrated in neurophysiological studies. The dibilitating effects of migraine are not confined to the attacks per se. Many individuals do not recover completely between the attacks and most report a negative impact on the most important life domains, and an interest in testing other treatments. Young persons have a higher frequency of attacks. Acute treatment should routinely be initiated with an analgesic plus a prokinetic anti-emetic. Triptans must not be provided early during the attack to ensure their efficacy. The natural course of attacks is commonly only temporarily altered by acute treatment. Non-pharmacological treatment and drugs may be equally viable in prophylaxis for migraine. In more complicated cases, conjoint therapy should be considered. New strategies to improve adherence with existing therapeutic regimens might yield greater benefits than will new pharmacological agents.

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.

After-effects of transcranial direct current stimulation (tDCS) on cortical spreading depression

Abnormal cortical excitability influences susceptibility to cortical spreading depression (CSD) in migraine. Because transcranial direct current stimulation (tDCS) is capable of inducing lasting changes of cortical excitability, we investigated the after-effects of tDCS on the propagation velocity of CSD in the rat. Twenty-five anesthetised rats received either anodal, cathodal or sham tDCS. The stimulation was applied for 20 min at a current strength of 200 microA after the recording of three baseline CSD measurements. Starting 5 min after tDCS, a further three CSDs were elicited and CSD velocity recorded at intervals of 20 min. tDCS and CSD recording was performed under anaesthesia with chloralose and urethane. As compared to the baseline velocity of 3.14 mm/min, anodal tDCS induced a significant increase of propagation velocity during the first post-tDCS recording (3.49 mm/min). In contrast to anodal tDCS, neither cathodal tDCS nor sham tDCS, which consisted of an initial ramped DC stimulation lasting only 20 s, showed a significant effect on CSD propagation velocity. As anodal tDCS is known to induce a lasting increase of cortical excitability in the clinical setting, our results support the notion that CSD propagation velocity reflects cortical excitability. Since cortical excitability and susceptibility to CSD is elevated in migraine patients, anodal tDCS - by increasing cortical excitability - might increase the probability of migraine attack in these patients, even beyond the end of its application.

Orofacial Pain--Part II: Assessment and management of vascular, neurovascular, idiopathic, secondary, and psychogenic causes

Chronic orofacial pain is a common health complaint faced by health practitioners today and constitutes a challenging diagnostic problem that often requires a multidisciplinary approach to diagnosis and treatment. The previous article by the same authors in this issue discussed the major clinical characteristics and the treatment of various musculoskeletal and neuropathic orofacial pain conditions. This second article presents aspects of vascular, neurovascular, and idiopathic orofacial pain, as well as orofacial pain due to various local, distant, or systemic diseases and psychogenic orofacial pain. The emphasis in this article is on the general differential diagnosis and various therapeutic regimens of each of these conditions. An accurate diagnosis is the key to successful treatment of chronic orofacial pain. Given that for many of the entities discussed in this article no curative treatment is available, current standards of management are emphasized. A comprehensive reference section has been included for those who wish to gain further information on a particular entity.

Transient global amnesia in a patient with high and persistent levels of antiphospholipid antibodies

Cerebrovascular disease is one of the most common symptoms associated with anticardiolipin antibodies (ACA) and lupus anticoagulant (LA), usually in the form of ischemic stroke. However, many other neurologic disorders have been described in patients with antiphospholipid syndrome or ACA. So far, the precise relation between the presence of antibodies and the development of the disease in many of these cases remain unknown. Transient global amnesia (TGA) is an infrequent neurologic disturbance whose precise pathophysiology is not known. It is characterized by a sudden inability to acquire new information, usually lasting no more than 12 h, and it is not accompanied by any other focal neurological signs or symptoms. We report a patient with TGA with persistent and high levels of ACA and LA and suggest that in patients with TGA, investigation of the possible presence of ACA and/or LA may be warranted because a higher prevalence of TGA in the patients with antiphospholipidic syndrome with respect to the general population may lead to further insights into pathogenesis of neurologic disease associated with antiphospholipidic antibodies.

Neuron-astrocyte interactions: partnership for normal function and disease in the central nervous system

Interactions between neurons and astrocytes are critical for signaling, energy metabolism, extracellular ion homeostasis, volume regulation, and neuroprotection in the central nervous system. Astrocytes face the synapses, send end-foot processes that enwrap the brain capillaries, and form an extensive network interconnected by gap junctions. Astrocytes express several membrane proteins and enzymes that are critical for uptake of glutamate at the synapses, ammonia detoxification, buffering of extracellular K+, and volume regulation. They also participate in detection, propagation, and modulation of excitatory synaptic signals, provide metabolic support to the active neurons, and contribute to functional hyperemia in the active brain tissue. Disturbances of these neuron-astrocyte interactions are likely to play an important role in neurologic disorders including cerebral ischemia, neurodegeneration, migraine, cerebral edema, and hepatic encephalopathy.

Visual disturbances and migraine

There is a close relationship between headache and the visual system. Visual symptoms are prominent features of clinical syndromes such as migraine, cluster headache, and the trigeminal autonomic cephalgias. There are also strong links between headache and the visual system on the basis of genetics, molecular biology, neurophysiology, and neuroimaging. Studies of these links are leading to the development of novel therapies for a variety of headache syndromes. This review is designed to summarize the most recent literature on headache and the visual system. A particular emphasis is placed on publications of interest to clinicians.

Late-phase long-term potentiation: getting to the nucleus

New mRNA must be transcribed in order to consolidate changes in synaptic strength. But how are events at the synapse communicated to the nucleus? Some research has shown that proteins can move from activated synapses to the nucleus. However, other work has shown that action potentials can directly inform the nucleus about cellular activation. Here we contend that action potential-induced signalling to the nucleus best meets the requirements of the consolidation of synapse-specific plasticity, which include both timing and stoichiometric constraints.

The blood-brain barrier/neurovascular unit in health and disease

The blood-brain barrier (BBB) is the regulated interface between the peripheral circulation and the central nervous system (CNS). Although originally observed by Paul Ehrlich in 1885, the nature of the BBB was debated well into the 20th century. The anatomical substrate of the BBB is the cerebral microvascular endothelium, which, together with astrocytes, pericytes, neurons, and the extracellular matrix, constitute a "neurovascular unit" that is essential for the health and function of the CNS. Tight junctions (TJ) between endothelial cells of the BBB restrict paracellular diffusion of water-soluble substances from blood to brain. The TJ is an intricate complex of transmembrane (junctional adhesion molecule-1, occludin, and claudins) and cytoplasmic (zonula occludens-1 and -2, cingulin, AF-6, and 7H6) proteins linked to the actin cytoskeleton. The expression and subcellular localization of TJ proteins are modulated by several intrinsic signaling pathways, including those involving calcium, phosphorylation, and G-proteins. Disruption of BBB TJ by disease or drugs can lead to impaired BBB function and thus compromise the CNS. Therefore, understanding how BBB TJ might be affected by various factors holds significant promise for the prevention and treatment of neurological diseases.

Topiramate monotherapy in epilepsy and migraineprevention

OBJECTIVES

The purposes of this review were to assess the efficacy of topiramate as monotherapy for epilepsy and migraine prevention, describe how it should be used, and give clinical advice on how to manage the practical aspects of dosing, titration, and possible adverse events in these 2 indications.

METHODS

We searched the PubMed and BIOSIS databases using the key words topiramate, epilepsy, and migraine from the year 1987 onward, and subsequently focused the search on larger controlled trial studies of topiramate as monotherapy.

RESULTS

Studies have evaluated the use of topiramate as monotherapy in the treatment of partial-onset and generalized seizures and in the prevention of migraine. In a randomized study, 75% of epilepsy patients treated with 400 mg/d topiramate remained seizure free at 1 year. Patients in the same study treated with a lower dose of topiramate (50 mg/d) also experienced notable seizure reductions, with 59% of patients free of seizures at 1 year. A comparison trial of topiramate (100 or 200 mg/d), valproate, and carbamazepine found that topiramate was associated with a similar time to first posttreatment seizure as the other 2 agents (P = NS). Trials of topiramate monotherapy in migraine prevention found that 100 mg/d was associated with a > or =50% reduction in monthly migraine frequency in 49% to 54% of patients. The migraine prevention trials typically used a starting dose of 25 mg/d, with weekly increases of 25 mg and an initial monotherapy target dose of 100 mg/d. The most common adverse events associated with topiramate are paresthesia, weight loss, and other centrally mediated symptoms, many of which may be ameliorated by proper titration and dosing and by good communication between physician and patient.

CONCLUSIONS

Data from controlled trials suggest that 100 mg/d topiramate as monotherapy is effective in the treatment of partial-onset and generalized seizures and in the prevention of migraine.