Paclitaxel-coated balloons in refractory nonanastomostic airway stenosis following lung transplantation.

Airway stenosis represents the commonest airway complication following lung transplantation, affecting between 7% and 18% of patients. Existing treatment options offer limited efficacy and can cause additional patient morbidity. Paclitaxel-coated balloons (PCB) have proved effective in managing postinterventional coronary artery re-stenosis. In a first-in-man study, we evaluated similar PCBs in refractory nonanastomotic airway stenosis in 12 patients. Following a single application, luminal patency was maintained in 50% at 270 days. No significant peri-interventional or early postinterventional complications occurred. Given these encouraging initial findings, further studies appear warranted.

Assessing the impact of dabigatran and warfarin on health-related quality of life: results from an RE-LY sub-study.

BACKGROUND: Anticoagulation is recommended in patients with atrial fibrillation (AF) to prevent strokes. Vitamin K antagonists, such as warfarin, are associated with numerous practical limitations--frequent anticoagulation monitoring, lifestyle and dietary restrictions--that complicate patient management and may impact health-related quality of life (HRQoL). This study derived HRQoL estimates for AF patients receiving warfarin or dabigatran etexilate (dabigatran), a new oral anticoagulant not requiring anticoagulation monitoring, during one year of stable treatment, i.e. in the absence of outcome events, such as strokes or major bleedings. METHODS: Changes in HRQoL over time and between treatments were assessed using the EQ-5D (utility and Visual Analogue Scale (VAS) scores) at baseline, 3 and 12 months in a sub-group of 1435 patients participating in the RE-LY trial. RE-LY was a phase III study that compared the safety and efficacy of warfarin, dabigatran 150 mg bid and dabigatran 110 mg bid for stroke prevention in patients with AF. RESULTS: Utilities ranged from 0.805 (dabigatran 150 mg bid) to 0.811 (dabigatran 110 mg bid) at baseline, and did not change over the one year observation period. No differences between the dabigatran groups and warfarin were statistically significant except for the dabigatran 150 mg bid group at 3 months. Similarly, none of the within-group or between-group differences in VAS scores were statistically significant. CONCLUSIONS: Over the course of one year, all anticoagulated patients without outcome events (e.g. strokes or major bleedings) had stable HRQoL. Scores between dabigatran and warfarin were comparable, which was unexpected given the known complexities of warfarin treatment.

Economic evaluation of dabigatran etexilate for the prevention of venous thromboembolism in patients aged over 75 years or with moderate renal impairment undergoing total knee or hip replacement.

Oral dabigatran etexilate is indicated for the prevention of venous thromboembolism (VTE) in patients undergoing total knee replacement or total hip replacement. We investigated the cost-effectiveness of the 150 mg once daily (od) dose recommended for patients aged over 75 or with moderate renal impairment, from a United Kingdom National Health Service perspective. Dabigatran etexilate was compared with subcutaneous enoxaparin 40 mg od, using a decision model. Risks for VTE and bleeding were derived from subgroup analyses of the phase III trials. Dabigatran etexilate was less costly than enoxaparin; cost savings varied from pound62 to pound274 (base-case analyses) and were primarily due to differences in administration costs. Results were robust across a range of sensitivity analyses. Dabigatran etexilate 150 mg od is cost saving compared with enoxaparin 40 mg od in patients aged over 75years and in patients with moderate renal impairment, with comparable efficacy and safety.

Selective upregulation of inducible nitric oxide synthase (iNOS) by lipopolysaccharide (LPS) and cytokines in microglia: in vitro and in vivo studies.

A role for free radicals has been proposed in infectious brain disease, where resident microglia cells upregulate the inducible nitric oxide synthase isoform (iNOS), and thus are capable of producing nitric oxide at enhanced rates. Using the constitutively expressed NADPH oxidase, microglial cells can generate superoxide, which reacts with nitric oxide to form the powerful oxidant peroxynitrite. In a mixed cell culture system of astrocytes and microglial cells, nitrite levels, used as an indicator of nitric oxide production, were elevated after the addition of lipopolysaccharide (LPS) and cytokines. Immunohistochemistry and the NADPH diaphorase technique demonstrated selective localization of the iNOS protein in microglial cells, whereas no iNOS protein or NADPH diaphorase activity was detected in astrocytes. A similar cellular distribution was observed in vivo following injection of LPS and cytokines into the rat striatum. By contrast, LPS and interferon-gamma led to translocation of NF-kappaB in microglia and in astrocytes, demonstrating that both cell types are responsive to the stimulus. Therefore, downstream control in iNOS expression is cell type-specific.

Nitrosative stress in primary glial cultures after induction of the inducible isoform of nitric oxide synthase (i-NOS).

Primary glial cultures are able to express the inducible isoform of nitric oxide synthase (i-NOS) upon stimulation by bacterial lipopolysaccharides (LPS) and gamma-interferon (gamma-IfN). Immunocytochemical studies revealed, that under our experimental conditions i-NOS is expressed exclusively by the microglial cells and not in the astrocytes. Nitric oxide (NO) formation represents an oxidative load for the microglial cells, as observed by the oxidation rate of the ROS- and peroxynitrite indicator dichloro-dihydrofluorescein (DCF-H) in these cells. However, cell viability was not affected by the nitric oxide formation, indicating some form of protection against the higher oxidative load. Upregulation of Mn-SOD in the mitochondria in the course of the induction of i-NOS and, compared to the astrocytes, higher GSH levels in the microglial cells probably explain the resistance of the cultures against nitrosative stress. Increased SOD-activities in the mitochondria could lower the superoxide concentration in this organelle and may prevent an oxidative and/or nitrosative damage via a decreased peroxynitrite formation. The higher GSH-levels in the microglial cells of unstimulated cultures represents a buffer which, under the conditions of i-NOS catalyzed NO-formation, prevents a decline of the microglial GSH-levels below that of the astrocytes.

Determination of nitric oxide metabolites by means of the Griess assay and gas chromatography-mass spectrometry in the cavernous and systemic blood of healthy males and patients with erectile dysfunction during different functional conditions of the penis.

Recent research implicated that the relaxation of cavernous arterial and trabecular smooth muscle-- the crucial event in penile erection--is initiated by the release of nitric oxide (NO) from nerve terminals within the cavernous tissue as well as from the endothelia that line the lacunar spaces and the intima of penile arteries. The present study was undertaken to determine whether plasma levels of the NO metabolites nitrate (NO3-) and nitrite (NO2-) in the systemic and cavernous blood of male subjects change during different penile conditions, and whether there is a difference in the NO3- and NO2- levels of normal males and patients with erectile dysfunction (ED). Twenty-four potent adult male volunteers and 15 patients with ED were exposed to visual and tactile erotic stimuli in order to elicit penile tumescence and, in the group of healthy volunteers, rigidity. Whole blood was aspirated from the corpus cavernosum and the cubital vein, and NO3- and NO2- levels were determined in plasma aliquots by means of the Griess reaction and a method combining gas chromatography and mass spectrometry (GC-MS). The mean systemic and cavernous plasma NO3-/NO2- level in blood samples obtained from the healthy volunteers was 25-31 microM when determined by means of the Griess reaction and 37-41 microM when measured by GC-MS. Both approaches revealed that NO3-/NO2- levels in the peripheral and cavernous blood do not change appreciably during developing erection, rigidity and detumescence. Moreover, no significant differences were found between NO3-/ NO2- plasma levels in the systemic and cavernous blood samples taken from the normal subjects and patients during penile flaccidity, tumescence and detumescence. Our results may reflect the fact that NO metabolism in the corpora cavernosa in the phases of penile tumescence and rigidity may account for only a minor fraction of local levels of NO3- and NO2-, which may also derive from exogenous sources. Moreover, the basal levels of NO metabolites in the blood flushing the lacunar spaces of the cavernous body in the state of developing erection could conceal any release of NO that may occur within the penile tissue. Thus, we conclude that the quantification of NO metabolites by means of advanced detection methods, such as GC-MS, is of no use in the workup of ED.

Cellular distribution of superoxide dismutases in the rat CNS.

Superoxide dismutase (SOD) is considered to be a major factor in protection of nervous tissue against excitotoxic and ischemic/hypoxic lesion. Controversial reports about the localization of SOD after such an insult prompted us to re-investigate immunocytochemically the localization of the enzyme in the brain and spinal cord using specific antibodies against the manganese (Mn-SOD) and copper/zinc (Cu/Zn-SOD) containing isoenzyme in combination with cell type specific markers. CNS tissue sections were analyzed by confocal laser scanning microscopy and digital photo imaging. Cu/Zn-SOD immunoreactivity was found to be located predominantly in astrocytes throughout the CNS. The staining was found in the cytoplasm, in cellular processes and, less intensive, in the nucleus sparing the nucleolus. At a lower level the enzyme was also detectable in neuronal perikarya and in structures of the neuropil. Motoneurons of the spinal cord displayed an enhanced Cu/Zn-SOD staining intensity, when compared to brain neurons. In contrast the Mn-containing isoenzyme was predominantly localized to neurons and their processes throughout the brain and the spinal cord. Confirming the mitochondrial localization of the enzyme, a granular staining pattern sparing the nucleus was observed. Mn-SOD stained mitochondria were also seen in astroglial cells but the staining intensity was, on the whole, much lower compared to neurons, and often hardly detectable. It seems reasonable to conclude that differences in the basal content of SOD-isoenzymes may contribute to different cellular susceptibilities in neurodegenerative processes that are accompanied by oxidative stress.

Induction of nitric oxide synthesis lowers intracellular glutathione in microglia of primary glial cultures.

Glutathione (GSH) is one of the most important antioxidants involved in detoxification of reactive oxygen and nitrogen species. We investigated the changes in intracellular GSH in primary glial cultures stimulated to produce inducible nitric oxide synthase and subsequently nitric oxide by bacterial lipopolysaccharide and gamma interferon treatment. Intracellular GSH content was measured by both the monochlorobimane fluorescence microscopy method and the GSH reductase recycling assay (Tietze. Anal Biochem 27:502-522, 1969.). Our results show that irrespective of the assay used the GSH content in stimulated cultures decreased to almost half that of control cultures. This decrease in GSH content was accompanied by an increase in S-nitrosoglutathione in the stimulated cultures. Analysis of the GSH related fluorescence images showed that the fluorescence intensity was lowered exclusively in microglial cells whereas that of astrocytes remained almost unchanged. The present study in conjunction with our previous investigation (Chatterjee et al. Glia 27:152-161, 1999) can be interpreted to imply that the higher GSH levels in untreated microglia are a mechanism to withstand nitric oxide synthase induced oxidative and nitrosative stress and therefore the GSH levels in microglia drop to astrocyte levels after induction.

Peroxynitrite mediated damage and lowered superoxide tolerance in primary cortical glial cultures after induction of the inducible isoform of NOS.

The effect of the induction of i-NOS in primary glial cultures was studied with respect to the protein levels of reactive oxygen species (ROS) scavenging enzymes and the cytotoxicity of nitric oxide (.NO) formation at different levels of artificially generated superoxide. Stimulation of the cultures by bacterial lipopolysaccharides and gamma-interferon resulted in an induction of i-NOS exclusively in microglial cells. Among the ROS scavenging enzymes superoxide dismutase (Cu/Zn- and Mn-isoform), glutathione peroxidase and catalase only mitochondrial Mn-SOD was found to be upregulated in the course of i-NOS induction (Western blots). Although .NO formation did not affect cell viability at physiological levels of superoxide over a time period of 4 days, it caused an oxidative load particularly in microglial cells as observed by monitoring the oxidation of dichloro-dihydrofluorescein, an indicator for the formation of peroxynitrite and ROS. Elevated levels of superoxide, generated either intracellularly by paraquat or extracellularly via xanthine oxidase and hypoxanthine, resulted dose-dependently in a larger decline of cell viability in the .NO forming cultures compared to controls (release of lactate dehydrogenase, citrate synthase, stainability by propidium iodide, and tetramethylrhodamine). NOS-inhibitors reduced the degree of cell damage to that seen for control cultures, indicating an ONOO--/.NO mediated mechanism of cell damage. Our data support the concept that i-NOS catalyzed .NO-formation leads to an ONOO--mediated increased oxidative load. At physiological levels of superoxide and within a wide range of higher superoxide levels this nitrosative stress is well balanced in cultured glial cells by protective mechanisms.

Glutathione levels in primary glial cultures: monochlorobimane provides evidence of cell type-specific distribution.

Because glutathione (GSH) levels in glia play an important role in cellular defense against oxidative and nitrosative stress, the present study was designed to study GSH levels in the primary glial cell cultures. Here we used fluorescence microscopy and spectroscopy with monochlorobimane for measurement of intracellular glutathione content. Monochlorobimane showed high specificity for GSH with very little binding to protein sulphydryls as ascertained from the low fluorescence intensity of the protein fraction of the cells as well as from the low fluorescence of the GSH-depleted cells. The formation of the monochlorobimane-glutathione conjugate was observed to be enzymatically catalyzed as seen from its higher rate of formation in the presence of cell homogenate. A monochlorobimane concentration of 60 microM was used for conjugation of cellular GSH; at higher mBCl concentrations there was no appreciable increase in fluorescence. Therefore, cultures were treated with 60 microM mBCl for an incubation time of 20 min (beyond this time, export of the bimane-glutathione adduct was significantly large) and examined by fluorescence microscopy. This adduct could be fixed with a mixture of paraformaldehyde and glutaraldehyde, and excellent fixation was observed with 4% paraformaldehyde and 0.2% glutaraldehyde. Analysis of the fluorescence images revealed differences in fluorescence intensity between astro- and microglial cells, which were identified by glial fibrilliary acidic protein and OX42 staining, respectively. Microglial cells isolated from primary glial cultures were found to have higher GSH content than astrocytes. Biochemical determination of GSH levels in microglia isolated from primary glial cultures corroborated this fact. From our findings it seems that owing to the greater intracellular concentration of reactive oxygen and nitrogen species to which microglia are subjected, especially under conditions of inflammation, this cell type is fortified with higher GSH levels as a means to combat oxidative and nitrosative stress.

Comparison of protein oxidation and aldehyde formation during oxidative stress in isolated mitochondria.

Oxidative stress is known to cause oxidative protein modification and the generation of reactive aldehydes derived from lipid peroxidation. Extent and kinetics of both processes were investigated during oxidative damage of isolated rat liver mitochondria treated with iron/ascorbate. The monofunctional aldehydes 4-hydroxynonenal (4-HNE), n-hexanal, n-pentanal, n-nonanal, n-heptanal, 2-octenal, 4-hydroxydecenal as well as thiobarbituric acid reactive substances (TBARS) were detected. The kinetics of aldehyde generation showed a lag-phase preceding an exponential increase. In contrast, oxidative protein modification, assessed as 2,4-dinitrophenylhydrazine (DNPH) reactive protein-bound carbonyls, continuously increased without detectable lag-phase. Western blot analysis confirmed these findings but did not allow the identification of individual proteins preferentially oxidized. Protein modification by 4-HNE, determined by immunoblotting, was in parallel to the formation of this aldehyde determined by HPLC. These results suggest that protein oxidation occurs during the time of functional decline of mitochondria, i.e. in the lag-phase of lipid peroxidation. This protein modification seems not to be caused by 4-HNE.

Enhanced cellular glutathione peroxidase immunoreactivity in activated astrocytes and in microglia during excitotoxin induced neurodegeneration.

The cellular distribution pattern of cellular glutathione peroxidase (GPx) was analyzed immunocytochemically in the normal rat central nervous system (CNS) and following exposure to the excitotoxin quinolinic acid (Quin). In the normal CNS, GPx was localized predominantly to microglia, identified by staining with isolectin B4 or the monoclonal antibody OX-42. Three days after intrastriatal administration of 90 pmoles Quin, GPx immunoreactivity was increased in activated microglia and also in astrocytes costained for glial fibrillary acidic protein (GFAP). Whereas GPx-positive astrocytes were seen predominantly in the environment of the lesion, most intensive immunoreactivity was located in globular-shaped microglia in the lesion core. GPx staining was generally low in neurons and failed to increase its intensity after lesion. In the case of excitotoxin-induced generation of oxygen-derived free radicals, the elevation of GPx levels in microglia, and likewise in activated astroglia, may provide an important mechanism to withstand oxidative stress.

Differential expression of superoxide dismutase isoforms in neuronal and glial compartments in the course of excitotoxically mediated neurodegeneration: relation to oxidative and nitrergic stress.

To examine the cellular distribution of radical scavenging enzymes in glia, in comparison to that in neurons and their behaviour during excitotoxically induced neurodegenerative processes, protein levels and the cellular localization of cytosolic and mitochondrial superoxide dismutase (Cu/Zn- and Mn-SOD) were investigated in the rat brain undergoing quinolinic acid (Quin)-induced neurodegeneration. Evidence for the specificity of the applied antibodies to detect immunocytochemically these SOD isoforms was obtained from electron microscopy and Western blotting. In control striatum Mn-SOD was clearly confined to neurons, whereas Cu/Zn-SOD was found, rather delicately, only in astrocytes. Microglia failed to stain with antibodies to both SOD isoforms. Quin application resulted in an initial formation of oxygen and nitrogen radicals as determined by the decline in the ratio of ascorbic to dehydroascorbic acid and by increased levels of nitrated proteins, an indicator for elevated peroxynitrite formation. Morphologically, massive neuronal damage was seen in parallel. Astroglia remained intact but showed initially decreased glutamine synthetase activities. The levels of Mn-SOD protein increased 2-fold 24 h after Quin injection (Western blotting) and declined only slowly over the time period considered (10 days). Cu/Zn-SOD levels increased only 1.3-fold. Immunocytochemical studies revealed that the increase in Mn-SOD is confined to neurons, whereas that of Cu/Zn-SOD was observed only in astroglial cells. Quiescent microglial cells were, as a rule, free of immunocytochemically detectable SOD, whereas in activated microglia a few Mn-SOD immunolabeled mitochondria occurred. Our results suggest a differential protective response in the Quin lesioned striatum in that Mn-SOD is upregulated in neurons and Cu/Zn-SOD in astroglia. Both SOD-isoforms are assumed to be induced to prevent oxidative and nitric oxide/peroxynitrite-mediated damage. In the border zone of the lesion core this strategy may contribute to resist the noxious stimulus.

2,7-Dihydrodichlorofluorescein diacetate as a fluorescent marker for peroxynitrite formation.

Reactive oxygen species (ROS) have been implicated as an important causative factor in cell damage, including apoptosis and necrosis. Their proposed actions comprise lipid peroxidation, DNA damage, destruction of the mitochondrial respiratory chain and protein modifications. Recent experiments underline the importance of peroxynitrite, the reaction product of the two potent reactive species nitric oxide and superoxide. Several fluorogenic compounds have been used in order to determine ROS formation in living cells. Besides dihydrorhodamine-123 (DHR-123), at present mostly applied to monitor peroxynitrite, 2,7-dihydrodichlorofluorescein (DCF-H) is used for detection of hydrogen peroxide and nitric oxide. We employed a cell free approach to evaluate the specificity and sensitivity of DCF-H to various oxidizing compounds. Our studies imply that DCF-H is much more sensitive to peroxynitrite oxidation than any other compound tested. In order to study peroxynitrite generation within individual cells, primary glial cultures loaded with DCF-H were monitored with a laser scanning microscope. Microglia, stimulated to simultaneously produce the peroxynitrite precursors nitric oxide and superoxide, displayed the greatest increase in DCF fluorescence, whereas microglia producing either nitric oxide or superoxide alone showed a relatively small increase in DCF fluorescence. In conclusion, DCF-H was demonstrated to be an excellent peroxynitrite marker with the potential to detect peroxynitrite formation in living cells.

Role of endogenous and exogenous antioxidants in the defence against functional damage and lipid peroxidation in rat liver mitochondria.

Mitochondria are cellular organelles where the generation of reactive oxygen species may be high. They are, however, effectively protected by their high capacities of antioxidative systems, as enzymes and either water or lipid soluble low molecular weight antioxidants. These antioxidative defence systems can be effectively regenerated after or during an oxidative stress as long as the mitochondria are in an energized state. Energization of mitochondria mainly depends on the availability of suitable respiratory substrates which can provide hydrogen for the reduction of either the glutathione- or alpha-tocopherol-system, since GSH is regenerated by glutathione reductase with the substrate NADPH and the alpha-tocopheroxyl-radical likely by reduced coenzyme Q. It was shown that mitochondria do not undergo damages as long as they can keep a high energy state. The delicate balance between prooxidative/antioxidative activities can be shifted towards oxidation, if experimentally prooxidants were added. After exhaustion of the antioxidative defence systems damages of mitochondrial functions become expressed followed by membrane injuries along with the oxidation and degradation of mitochondrial lipids and proteins leading finally to the total degradation of the mitochondria. Extramitochondrial antioxidants may assist the mitochondrial antioxidative defence systems in a complex way, whereby particularly ascorbic acid can act both as prooxidant and as antioxidant.

Immunocytochemistry of endothelial nitric oxide synthase in the rat brain: a light and electron microscopical study using the tyramide signal amplification technique.

There are many inconsistencies in the literature about the cellular and subcellular distribution of the endothelial isoform of nitric oxide synthase (eNOS) in the brain. We have re-investigated its localization by light and electron microscopical (LM, EM) immunocytochemistry and the NADPH-diaphorase reaction. Using bovine aortic tissue as a positive control the protocols for the fixation and staining procedure were optimized. Only cryosections immersion-fixed with aceton and a mixture of aldehydes exhibited a clear-cut immunostaining. In rat brain tissue the endothelium of the entire vasculature showed immunoreactivity and, in addition to that, the epithelial cells of the choroid plexuses, whereas neurons never displayed any signs of immunostaining. EM immunoprecipitates were seen irregularly distributed in the cytosol or attached to endocellular membranes. EM NADPH-diaphorase histochemistry using the tetrazolium salt BSPT provided incoherent pictures in so far as the reaction product was exclusively bound to membranes. The restriction of eNOS within brain tissue to the vasculature may have implications for the differential significance of NOS isoforms in brain function.

Patterns of nitric oxide synthase at the messenger RNA and protein levels during early rat brain development.

There is substantial evidence that the intra- and intercellular messenger nitric oxide, generated enzymatically from L-arginine by nitric oxide synthase in different isoforms, is involved in the development of nervous tissue. In this study we investigated the nitric oxide expression in the pre- and postnatally developing rat brain. With regard to messenger RNA, all of the basic nitric oxide synthase isoforms (neuronal, endothelial and macrophage nitric oxide synthase) were already expressed at embryonic day 10 and showed a temporary decrease at embryonic day 17. Western blot analysis of the three isoform proteins revealed a time pattern that was different from those of messenger RNAs. Although the endothelial nitric oxide synthase isoform was also expressed at embryonic day 10, no quantitative changes were observed over the whole time period studied. Protein amounts of brain and inducible nitric oxide synthase were first detectable at embryonic day 15, with a tendency to rise. A parallel time pattern was found for the NADPH-diaphorase activity in our light microscopic studies, whereas ultrastructurally the reaction product was seen in the brain pallium even of 13-day-old embryos. The data indicate a permanent presence of the transcripts for all nitric oxide synthase isoforms in the rat central nervous system from embryonic day 10 onwards, although the expression of respective proteins and staining patterns may differ.

Angiotensin-converting enzyme inhibition and the norepinephrine spillover response to dynamic exercise.

To determine whether prejunctional angiotensin II receptors facilitate norepinephrine (NE) release during exercise, normal volunteers exercised at approximately 25 or approximately 65% of maximal O2 consumption (VO2max) on two occasions. Steady-state NE kinetics were determined at rest and during exercise by using infusions of [3H]NE. Arterial plasma NE and [3H]NE were determined for calculation of NE spillover and clearance. Before the second bout of exercise at approximately 25% of VO2max later that day, enalaprilat (n = 8) or nitroprusside (n = 5) was administered intravenously to lower blood pressure to a comparable level and saline was infused as a time control (n = 4). Exercise at 25% of VO2max increased heart rate from 73 to 100 beats/min, plasma NE from 296 to 626 pg/ml, and NE spillover from 1.56 to 3.32 nmol.min-1.m-2. The exercise effect was significant in each subgroup. At rest and during exercise, the decrease in blood pressure and the increase in plasma NE and NE spillover were similar with enalaprilat and nitroprusside. There was no drug effect in the saline group. In a separate group (n = 7), exercise at approximately 65% of VO2max increased heart rate from 76 to 170 beats/min, plasma NE from 338 to 2,656 pg/ml, and NE spillover from 1.87 to 11.65 nmol.min-1.m-2. In this group, 3 days of oral enalapril did not affect the NE spillover response to exercise. Because the angiotensin-converting enzyme inhibitor did not attenuate the NE spillover response to exercise, we conclude that at the exercise levels tested, prejunctional angiotensin II receptors do not appear to facilitate NE release.

Migraine: definitions, mechanisms, and treatment.

Although ubiquitous, migraine remains incompletely understood and thus often ineffectively managed. Fortunately, new advances in our understanding of migraine's origins have led to identification and application of therapeutic intervention that is unparalleled in its specificity and clinical efficacy. We present a unified model of migraine genesis and explain how application of the model to clinical practice may improve therapeutic management of this common disorder.