Noradrenergic agonists and antagonists influence migration of cortical spreading depression in rat-a possible mechanism of migraine prophylaxis and prevention of postischemic neuronal damage

Cold Case of Thrombolysis: Cold Recombinant Tissue Plasminogen Activator Confers Enhanced Neuroprotection in Experimental Stroke

Background Thrombolysis and endovascular thrombectomy are the primary treatment for ischemic stroke. However, due to the limited time window and the occurrence of adverse effects, only a small number of patients can genuinely benefit from recanalization. Intraarterial injection of rtPA (recombinant tissue plasminogen activator) based on arterial thrombectomy could improve the prognosis of patients with acute ischemic stroke, but it could not reduce the incidence of recanalization-related adverse effects. Recently, selective brain hypothermia has been shown to offer neuroprotection against stroke. To enhance the recanalization rate of ischemic stroke and reduce the adverse effects such as tiny thrombosis, brain edema, and hemorrhage, we described for the first time a combined approach of hypothermia and thrombolysis via intraarterial hypothermic rtPA. Methods and Results We initially established the optimal regimen of hypothermic rtPA in adult rats subjected to middle cerebral artery occlusion. Subsequently, we explored the mechanism of action mediating hypothermic rtPA by probing reduction of brain tissue temperature, attenuation of blood-brain barrier damage, and sequestration of inflammation coupled with untargeted metabolomics. Hypothermic rtPA improved neurological scores and reduced infarct volume, while limiting hemorrhagic transformation in middle cerebral artery occlusion rats. These therapeutic outcomes of hypothermic rtPA were accompanied by reduced brain temperature, glucose metabolism, and blood-brain barrier damage. A unique metabolomic profile emerged in hypothermic rtPA-treated middle cerebral artery occlusion rats characterized by downregulated markers for energy metabolism and inflammation. Conclusions The innovative use of hypothermic rtPA enhances their combined, as opposed to stand-alone, neuroprotective effects, while reducing hemorrhagic transformation in ischemic stroke.

Mild hypothermia reduces spreading depolarizations and infarct size in a swine model

Spreading depolarizations (SDs) have been linked to infarct volume expansion following ischemic stroke. Therapeutic hypothermia provides a neuroprotective effect after ischemic stroke. This study aimed to evaluate the effect of hypothermia on the propagation of SDs and infarct volume in an ischemic swine model. Through left orbital exenteration, middle cerebral arteries were surgically occluded (MCAo) in 16 swine. Extensive craniotomy and durotomy were performed. Six hypothermic and five normothermic animals were included in the analysis. An intracranial temperature probe was placed right frontal subdural. One hour after ischemic onset, mild hypothermia was induced and eighteen hours of electrocorticographic (ECoG) and intrinsic optical signal (IOS) recordings were acquired. Postmortem, 4 mm-thick slices were stained with 2,3,5-triphenyltetrazolium chloride to estimate the infarct volume. Compared to normothermia (36.4 ± 0.4°C), hypothermia (32.3 ± 0.2°C) significantly reduced the frequency and expansion of SDs (ECoG: 3.5 ± 2.1, 73.2 ± 5.2% vs. 1.0 ± 0.7, 41.9 ± 21.8%; IOS 3.9 ± 0.4, 87.6 ± 12.0% vs. 1.4 ± 0.7, 67.7 ± 8.3%, respectively). Further, infarct volume among hypothermic animals (23.2 ± 1.8% vs. 32.4 ± 2.5%) was significantly reduced. Therapeutic hypothermia reduces infarct volume and the frequency and expansion of SDs following cerebral ischemia.

Trigeminovascular effects of propranolol in men and women, role for sex steroids

Objective

Assess whether propranolol modulates the trigeminovascular system in both men and women.

Methods

We investigated the effect of propranolol (80 mg, 90 min after oral administration, corresponding to T_max) on the increase in dermal blood flow of the forehead skin (innervated by the trigeminal nerve) by capsaicin application (0.6 mg/mL) and electrical stimulation (0.2–1.0 mA) before and after placebo (grapefruit juice) or propranolol (oral solution diluted in grapefruit juice) in a randomized, double‐blind, placebo‐controlled cross‐over study, including healthy males (n = 10) and females on contraceptives (n = 11). Additionally, we compared our results with data from the Dutch IADB.nl prescription database by analyzing the change in triptan use after propranolol prescription in a population similar to our dermal blood flow study subjects (males and females, 20–39 years old).

Results

Dermal blood flow responses to capsaicin were significantly attenuated after propranolol, but not after placebo. When stratifying by sex, no significant changes in the capsaicin‐induced dermal blood flow were observed in females after propranolol, whereas they remained significant in males. Dermal blood flow responses to electrical stimulation were not modified in any case. In our prescription database study, after propranolol, a more pronounced decrease in triptan use was observed in male patients than in female patients.

Interpretation

Propranolol (80 mg) inhibits capsaicin‐induced increases in dermal blood flow in a sex‐dependent manner. In patients, a more pronounced decrease in triptan use is observed in males when compared with females, suggesting an interaction between propranolol and sex steroids in the modulation of the trigeminovascular system.

Efficacy profile of noninvasive vagus nerve stimulation on cortical spreading depression susceptibility and the tissue response in a rat model

Background

Noninvasive vagus nerve stimulation (nVNS) has recently emerged as a promising therapy for migraine. We previously demonstrated that vagus nerve stimulation inhibits cortical spreading depression (CSD), the electrophysiological event underlying migraine aura and triggering headache; however, the optimal nVNS paradigm has not been defined.

Methods

Various intensities and doses of nVNS were tested to improve efficacy on KCl-evoked CSD frequency and electrical threshold of CSD in a validated rat model. Chronic efficacy was evaluated by daily nVNS delivery for four weeks. We also examined the effects of nVNS on neuroinflammation and trigeminovascular activation by western blot and immunohistochemistry.

Results

nVNS suppressed susceptibility to CSD in an intensity-dependent manner. Two 2-minute nVNS 5 min apart afforded the highest efficacy on electrical CSD threshold and frequency of KCl-evoked CSD. Daily nVNS for four weeks did not further enhance efficacy over a single nVNS 20 min prior to CSD. The optimal nVNS also attenuated CSD-induced upregulation of cortical cyclooxygenase-2, calcitonin gene-related peptide in trigeminal ganglia, and c-Fos expression in trigeminal nucleus caudalis.

Conclusions

Our study provides insight on optimal nVNS parameters to suppress CSD and suggests its benefit on CSD-induced neuroinflammation and trigeminovascular activation in migraine treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10194-022-01384-1.

Propranolol modulation of tetrodotoxin-resistant Na+ channels in dural afferent neurons

Propranolol, a representative adrenergic β-receptor antagonist, is widely used to prevent migraine attacks. Although propranolol is well known to inhibit tetrodotoxin-resistant (TTX-R) Na+ channels in cardiac myocytes, it is unclear whether the drug modulates these channels expressed in dural afferent neurons. In this study, we examined the effects of propranolol on TTX-R Na+ channels in medium-sized dural afferent neurons identified by the fluorescent dye DiI. The TTX-R Na+ currents (INa) were recorded from acutely isolated DiI-positive neurons using a whole-cell patch clamp technique under voltage-clamp conditions. Propranolol inhibited the noninactivating steady-state component more potently than the peak component of transient TTX-R INa. Propranolol also potently inhibited the slow voltage ramp-induced TTX-R INa in a concentration-dependent manner, suggesting that it preferentially inhibited the noninactivating or persistent INa in DiI-positive neurons. Propranolol had little effect on voltage dependence, but it increased the extent of the use-dependent inhibition of TTX-R Na+ channels. Propranolol also accelerated the onset of inactivation and retarded recovery from inactivation in these channels. Under current-clamp conditions, propranolol decreased the number of action potentials elicited by depolarizing current stimuli. In conclusion, the propranolol-mediated preferential inhibition of persistent INa and modulation of the inactivation kinetics of TTX-R Na+ channels might represent additional mechanisms for migraine prophylaxis.

Central sympathetic nerve activation in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a life-threatening condition, and although its two main complications-cerebral vasospasm (CVS)/delayed cerebral ischemia (DCI) and early brain injury (EBI)-have been widely studied, prognosis has not improved over time. The sympathetic nerve (SN) system is important for the regulation of cardiovascular function and is closely associated with cerebral vessels and the regulation of cerebral blood flow and cerebrovascular function; thus, excessive SN activation leads to a rapid breakdown of homeostasis in the brain. In the hyperacute phase, patients with SAH can experience possibly lethal conditions that are thought to be associated with SN activation (catecholamine surge)-related arrhythmia, neurogenic pulmonary edema, and irreversible injury to the hypothalamus and brainstem. Although the role of the SN system in SAH has long been investigated and considerable evidence has been collected, the exact pathophysiology remains undetermined, mainly because the relationships between the SN system and SAH are complicated, and many SN-modulating factors are involved. Thus, research concerning these relationships needs to explore novel findings that correlate with the relevant concepts based on past reliable evidence. Here, we explore the role of the central SN (CSN) system in SAH pathophysiology and provide a comprehensive review of the functional CSN network; brain injury in hyperacute phase involving the CSN system; pathophysiological overlap between the CSN system and the two major SAH complications, CVS/DCI and EBI; CSN-modulating factors; and SAH-related extracerebral organ injury. Further studies are warranted to determine the specific roles of the CSN system in the brain injuries associated with SAH.

A critical review of the neurovascular nature of migraine and the main mechanisms of action of prophylactic antimigraine medications

INTRODUCTION

Migraine involves neurovascular, functional, and anatomical alterations. Migraineurs experience an intense unilateral and pulsatile headache frequently accompanied with vomiting, nausea, photophobia, etc. Although there is no ideal preventive medication, frequency in migraine days may be partially decreased by some prophylactics, including antihypertensives, antidepressants, antiepileptics, and CGRPergic inhibitors. However, the mechanisms of action involved in antimigraine prophylaxis remain elusive.

AREAS COVERED

This review recaps some of the main neurovascular phenomena related to migraine and currently available preventive medications. Moreover, it discusses the major mechanisms of action of the recommended prophylactic medications.

EXPERT OPINION

In the last three years, migraine prophylaxis has evolved from nonspecific to specific antimigraine treatments. Overall, nonspecific treatments  mainly involve neural actions, whereas specific pharmacotherapy (represented by CGRP receptor antagonists and CGRPergic monoclonal antibodies) is predominantly mediated by neurovascular mechanisms that may include, among others: (i) reduction in the cortical spreading depression (CSD)-associated events; (ii) inhibition of pain sensitization; (iii) blockade of neurogenic inflammation; and/or (iv) increase in cranial vascular tone. Accordingly, the novel antimigraine prophylaxis promises to be more effective, devoid of significant adverse effects (unlike nonspecific treatments), and more beneficial for the quality of life of migraineurs.

Vagus nerve stimulation inhibits cortical spreading depression exclusively through central mechanisms

Experimental and clinical data strongly support vagus nerve stimulation (VNS) as a novel treatment in migraine. Vagus nerve stimulation acutely suppresses cortical spreading depression (CSD) susceptibility, an experimental model that has been used to screen for migraine therapies. However, mechanisms underlying VNS efficacy on CSD are unknown. Here, we interrogated the central and peripheral mechanisms using VNS delivered either invasively (iVNS) or noninvasively (nVNS) in male Sprague-Dawley rats. Cortical spreading depression susceptibility was evaluated 40 minutes after the stimulation. iVNS elevated the electrical CSD threshold more than 2-fold and decreased KCl-induced CSD frequency by 22% when delivered to intact vagus nerve. Distal vagotomy did not alter iVNS efficacy (2-fold higher threshold and 19% lower frequency in iVNS vs sham). By contrast, proximal vagotomy completely abolished iVNS effect on CSD. Pharmacological blockade of nucleus tractus solitarius, the main relay for vagal afferents, by lidocaine or glutamate receptor antagonist CNQX also prevented CSD suppression by nVNS. Supporting a role for both norepinephrine and serotonin, CSD suppression by nVNS was inhibited by more than 50% after abrogating norepinephrinergic or serotonergic neurotransmission alone using specific neurotoxins; abrogating both completely blocked the nVNS effect. Our results suggest that VNS inhibits CSD through central afferents relaying in nucleus tractus solitarius and projecting to subcortical neuromodulatory centers providing serotonergic and norepinephrinergic innervation to the cortex.

Adrenergic inhibition facilitates normalization of extracellular potassium after cortical spreading depolarization

Cortical spreading depolarization (CSD) is a propagating wave of tissue depolarization characterized by a large increase of extracellular potassium concentration and prolonged subsequent electrical silencing of neurons. Waves of CSD arise spontaneously in various acute neurological settings, including migraine aura and ischemic stroke. Recently, we have reported that pan-inhibition of adrenergic receptors (AdRs) facilitates the normalization of extracellular potassium after acute photothrombotic stroke in mice. Here, we have extended that mechanistic study to ask whether AdR antagonists also modify the dynamics of KCl-induced CSD and post-CSD recovery in vivo. Spontaneous neural activity and KCl-induced CSD were visualized by cortex-wide transcranial Ca²⁺ imaging in G-CaMP7 transgenic mice. AdR antagonism decreased the recurrence of CSD waves and accelerated the post-CSD recovery of neural activity. Two-photon imaging revealed that astrocytes exhibited aberrant Ca²⁺ signaling after passage of the CSD wave. This astrocytic Ca²⁺ activity was diminished by the AdR antagonists. Furthermore, AdR pan-antagonism facilitated the normalization of the extracellular potassium level after CSD, which paralleled the recovery of neural activity. These observations add support to the proposal that neuroprotective effects of AdR pan-antagonism arise from accelerated normalization of extracellular K⁺ levels in the setting of acute brain injury.

Noradrenaline modulates neuronal and perceptual visual detectability via β-adrenergic receptor

RATIONALE

Noradrenaline (NA) is a neuromodulator secreted from noradrenergic neurons in the locus coeruleus to the whole brain depending on the physiological state and behavioral context. It regulates various brain functions including vision via three major adrenergic receptor (AR) subtypes. Previous studies investigating the noradrenergic modulations on vision reported different effects, including improvement and impairment of perceptual visual sensitivity in rodents via β-AR, an AR subtype. Therefore, it remains unknown how NA affects perceptual visual sensitivity via β-AR and what neuronal mechanisms underlie it.

OBJECTIVES

The current study investigated the noradrenergic modulation of perceptual and neuronal visual sensitivity via β-AR in the primary visual cortex (V1).

METHODS

We performed extracellular multi-point recordings from V1 of rats performing a go/no-go visual detection task under the head-fixed condition. A β-AR blocker, propranolol (10 mM), was topically administered onto the V1 surface, and the drug effect on behavioral and neuronal activities was quantified by comparing pre-and post-drug administration.

RESULTS

The topical administration of propranolol onto the V1 surface significantly improved the task performance. An analysis of the multi-unit activity in V1 showed that propranolol significantly suppressed spontaneous activity and facilitated the visual response of the recording sites in V1. We further calculated the signal-to-noise ratio (SNR), finding that the SNR was significantly improved after propranolol administration.

CONCLUSIONS

Pharmacological blockade of β-AR in V1 improves perceptual visual detectability by modifying the SNR of neuronal activity.

Clinical and vascular responses to propranolol and candesartan in migraine patients: A randomized controlled clinical trial

Background:

Both propranolol and candesartan are prophylactic drugs for migraine, but with unknown mechanisms of action. The objectives of the present study were to investigate these drugs’ effects on arterial wall dynamics and the potential relation between their vascular and clinical effect.

Methods:

The study was based on data from a previously published randomized, placebo-controlled, triple-blinded, double crossover clinical trial comparing the prophylactic effects of candesartan and propranolol in 72 patients. Finapres noninvasive blood pressure curves were analyzed. On the descending limb of the pulse curve, a notch is produced by pulse wave reflection, and its relative height compared to the top of the curve (the notch ratio) was used as a marker of arterial wall stiffness.

Results:

Candesartan decreased the notch ratio from baseline ( p = 0.005), reflecting more compliant arteries and vasodilation, whereas propranolol increased the notch ratio ( p = 0.005), reflecting less compliant arteries and vasoconstriction. There was no difference in baseline notch ratio between clinical responders and nonresponders.

Conclusion:

The drugs are both efficient prophylactic medications, yet they have opposite effects on arterial wall dynamics. This suggests that drug effects other than those on arterial compliance must be responsible for their prophylactic effect in migraine.

[Migraine prophylaxis-all just antibodies? : Medical and nonmedical migraine preventive treatment in times of CGRP antibodies]

BACKGROUND

Migraine is a frequently underdiagnosed disease that is associated with a high burden on affected patients. There are a variety of prophylactic treatment options available, that have been expanded with the introduction of the CGRP-(receptor-)antibodies.

OBJECTIVES

Status of pharmacologic and nonpharmacologic preventive treatment in migraine therapy.

METHODS

Analysis and evaluation of internationally published articles concerning preventive treatment of episodic and chronic migraine.

RESULTS

There are many approved medications for migraine prophylaxis with different evidence. The possibilities were further expanded with CGRP antibodies. Comparative studies of the new antibodies with previous prophylactic drugs have not yet been published, so it's unclear whether the antibodies are therapeutically superior. What should be emphasized is their rapid onset of action and their good tolerance. Basically, an individual choice of prophylaxis, which is based on affectedness, comorbidities and comedication, makes sense. In addition, a combination with nondrug measures is always mandatory.

CONCLUSIONS

A variety of medicinal and non-medicinal measures are available for the treatment of migraine, which should be used multimodally.

Vagus nerve stimulation reduces spreading depolarization burden and cortical infarct volume in a rat model of stroke

Cortical spreading depolarization (SD) waves negatively affect neuronal survival and outcome after ischemic stroke. We here aimed to investigate the effects of vagus nerve stimulation (VNS) on SDs in a rat model of focal ischemia. To this end, we delivered non-invasive VNS (nVNS) or invasive VNS (iVNS) during permanent middle cerebral artery occlusion (MCAO), and found that both interventions significantly reduced the frequency of SDs in the cortical peri-infarct area compared to sham VNS, without affecting relative blood flow changes, blood pressure, heart rate or breathing rate. In separate groups of rats subjected to transient MCAO, we found that cortical stroke volume was reduced 72 h after transient MCAO, whereas stroke volume in the basal ganglia remained unchanged. In rats treated with nVNS, motor outcome was improved 2 days after transient MCAO, but was similar to sham VNS animals 3 days after ischemia. We postulate that VNS may be a safe and efficient intervention to reduce the clinical burden of SD waves in stroke and other conditions.

Therapeutic implications of cortical spreading depression models in migraine

Migraine is among the most common and disabling neurological diseases in the world. Cortical spreading depression (CSD) is a wave of near-complete depolarization of neurons and glial cells that slowly propagates along the cortex creating the perception of aura. Evidence suggests that CSD can trigger migraine headache. Experimental models of CSD have been considered highly translational as they recapitulate migraine-related phenomena and have been validated for screening migraine therapeutics. Here we outline the essential components of validated experimental models of CSD and provide a comprehensive review of potential modulators and targets against CSD. We further focus on novel interventions that have been recently shown to suppress CSD susceptibility that may lead to therapeutic targets in migraine.

Systematic review of the pharmacological agents that have been tested against spreading depolarizations

Spreading depolarization (SD) occurs alongside brain injuries and it can lead to neuronal damage. Therefore, pharmacological modulation of SD can constitute a therapeutic approach to reduce its detrimental effects and to improve the clinical outcome of patients. The major objective of this article was to produce a systematic review of all the drugs that have been tested against SD. Of the substances that have been examined, most have been shown to modulate certain SD characteristics. Only a few have succeeded in significantly inhibiting SD. We present a variety of strategies that have been proposed to overcome the notorious harmfulness and pharmacoresistance of SD. Information on clinically used anesthetic, sedative, hypnotic agents, anti-migraine drugs, anticonvulsants and various other substances have been compiled and reviewed with respect to the efficacy against SD, in order to answer the question of whether a drug at safe doses could be of therapeutic use against SD in humans.

Propranolol treatment prevents chronic central sensitization induced by repeated dural stimulation

Migraine is currently conceptualized as a chronic disease with episodic manifestations. In some patients, migraine attack frequency increases, leading to chronic migraine. Daily preventive therapy is initiated to decrease attack frequency. Propranolol, a first-line medication for migraine prophylaxis, reduces attack frequency in nearly 50% of patients receiving it. However, the mechanisms of its antimigraine action are unclear. We examined the effect of daily propranolol treatment (10 mg·kg per os, 8 days) in a rat model of recurrent activation of dural nociceptors (repeated infusion of an inflammatory soup (IS) on the dura through a cannula every 2-3 days). Propranolol does not abort IS-induced acute cephalic mechanical allodynia but blocks the development of a chronic cutaneous hypersensitivity upon repeated IS injections. Furthermore, propranolol prevents (1) the elevated touch-evoked Fos expression within the trigeminocervical complex, (2) enhanced both spontaneous activity, and evoked responses of second-order trigeminovascular neurons, (3) elevated touch-evoked rostral ventromedial medulla and locus coeruleus Fos expression and (4) diffuse noxious inhibitory controls impairment, induced by repeated IS injections. Our results suggest that propranolol exerts its prophylactic action, at least in part, by blocking the chronic sensitization of descending controls of pain, arising from the rostral ventromedial medulla and locus coeruleus, and in turn preventing the maintenance of a state of facilitated trigeminovascular transmission within the trigeminocervical complex. Assessing changes in these brain areas has the potential to elucidate the mechanisms for migraine transformation and to reveal novel biological and molecular targets for specific migraine-preventive therapies.

Modulation of brainstem activity and connectivity by respiratory-gated auricular vagal afferent nerve stimulation in migraine patients

Migraine pathophysiology includes altered brainstem excitability, and recent neuromodulatory approaches aimed at controlling migraine episodes have targeted key brainstem relay and modulatory nuclei. In this study, we evaluated the impact of respiratory-gated auricular vagal afferent nerve stimulation (RAVANS), a novel neuromodulatory intervention based on an existing transcutaneous vagus nerve stimulation approach, in the modulation of brainstem activity and connectivity in migraine patients. We applied 3T-functional magnetic resonance imaging with improved in-plane spatial resolution (2.62 × 2.62 mm) in episodic migraine (interictal) and age- and sex-matched healthy controls to evaluate brain response to RAVANS (gated to either inhalation or exhalation) and sham stimulation. We further investigated RAVANS modulation of tactile trigeminal sensory afference response in the brainstem using air-puff stimulation directed to the forehead during functional magnetic resonance imaging. Compared with sham and inhalatory-gated RAVANS (iRAVANS), exhalatory-gated RAVANS (eRAVANS) activated an ipsilateral pontomedullary region consistent with nucleus tractus solitarii (NTS). During eRAVANS, NTS connectivity was increased to anterior insula and anterior midcingulate cortex, compared with both sham and iRAVANS, in migraine patients. Increased connectivity was inversely correlated with relative time to the next migraine attack, suggesting clinical relevance to this change in connectivity. Poststimulation effects were also noted immediately after eRAVANS, as we found increased activation in putative pontine serotonergic (ie, nucleus raphe centralis) and noradrenergic (ie, locus coeruleus) nuclei in response to trigeminal sensory afference. Regulation of activity and connectivity of brainstem and cortical regions involved in serotonergic and noradrenergic regulation and pain modulation may constitute an underlying mechanism supporting beneficial clinical outcomes for eRAVANS applied for episodic migraine.

Current Prophylactic Medications for Migraine and Their Potential Mechanisms of Action

A relatively high number of different medications is currently used for migraine prevention in clinical practice. Although these compounds were initially developed for other indications and differ in their mechanisms of action, some general themes can be identified from the mechanisms at play. Efficacious preventive drugs seem to either suppress excitatory nervous signaling via sodium and/or calcium receptors, facilitate GABAergic inhibition, reduce neuronal sensitization, block cortical spreading depression and/or reduce circulating levels of CGRP. We here review such mechanisms for the different compounds.

Arguments against the role of cortical spreading depression in migraine

Cortical spreading depression (CSD) is a wave of increased electrocortical activity and vasodilation, followed by sustained decreased activity and prolonged vasoconstriction. Although the discovery of CSD has been ascribed to Leão, rather than vasoconstriction, he only observed a depression of neural activity combined with vasodilation, with much weaker stimulation than used by his followers. There is a longstanding belief that CSD underlies migraine aura, with its positive symptoms such as mosaic patterns and its negative symptoms such as scotoma, and a similar propagation speed and vasoreaction pattern. However, there are many arguments against this theory. CSD is difficult to evoke in man, and electroencephalography (EEG) readings are not flattened during migraine (as opposed to EEG during CSD). Moreover, in contrast to CSD, migraine can occur bilaterally, and is not accompanied by a disrupted blood-brain barrier, increased cerebral metabolism, or cerebral cell swelling. Calcitonin gene-related peptide, which is thought to be characteristic of migraine pain, is increased in the blood from the external jugular vein during migraine in humans, but not during CSD in cats or rats. Moreover, CSD does not explain the appearance of premonitory symptoms or allodynia, long before the actual onset of aura. In addition, there is a variation in the pain mechanisms of migraine and CSD, and in their reaction to transcranial magnetic stimulation and several pharmacologic interventions. Finally, the origin of putative CSD in migraine is currently unknown.

Novel Therapeutic Targets Against Spreading Depression

Migraine is among the most prevalent and disabling neurological diseases in the world. Cortical spreading depression (SD) is an intense wave of neuronal and glial depolarization underlying migraine aura, and a headache trigger, which has been used as an experimental platform for drug screening in migraine. Here, we provide an overview of novel therapeutic targets that show promise to suppress SD, such as acid-sensing ion channels, casein kinase Iδ, P2X7-pannexin 1 complex, and neuromodulation, and outline the experimental models and essential quality measures for rigorous and reproducible efficacy testing.

Recurrent administration of the nitric oxide donor, isosorbide dinitrate, induces a persistent cephalic cutaneous hypersensitivity: A model for migraine progression

Background

A subgroup of migraineurs experience an increase in attack frequency leading to chronic migraine.

Methods

We assessed in rats the roles of dose and repeat administration of systemic isosorbide dinitrate (ISDN), a nitric oxide donor, on the occurrence and development of cephalic/face and extracephalic/hindpaw mechanical allodynia as a surrogate of migraine pain, and the effect of acute systemic sumatriptan and olcegepant and chronic systemic propranolol on these behavioral changes.

Results

A single high (H-ISDN) but not low (L-ISDN) dose of ISDN induces a reversible cephalic and extracephalic mechanical allodynia. However, with repeat administration, L-ISDN produces reversible cephalic but never extracephalic allodynia, whereas H-ISDN induces cephalic and extracephalic allodynia that are both potentiated. H-ISDN-induced cephalic allodynia thus gains persistency. Sumatriptan and olcegepant block single H-ISDN-induced behavioral changes, but only olcegepant reduces these acute changes when potentiated by repeat administration. Neither sumatriptan nor olcegepant prevent chronic cephalic hypersensitivity. Conversely, propranolol blocks repeat H-ISDN-induced chronic, but not acute, behavioral changes.

Conclusions

Repeated ISDN administration appears to be a naturalistic rat model for migraine progression, suitable for screening acute and preventive migraine therapies. It suggests frequent and severe migraine attacks associated with allodynia may be a risk factor for disease progression.

Vagus nerve stimulation inhibits cortical spreading depression

Vagus nerve stimulation has recently been reported to improve symptoms of migraine. Cortical spreading depression is the electrophysiological event underlying migraine aura and is a trigger for headache. We tested whether vagus nerve stimulation inhibits cortical spreading depression to explain its antimigraine effect. Unilateral vagus nerve stimulation was delivered either noninvasively through the skin or directly by electrodes placed around the nerve. Systemic physiology was monitored throughout the study. Both noninvasive transcutaneous and invasive direct vagus nerve stimulations significantly suppressed spreading depression susceptibility in the occipital cortex in rats. The electrical stimulation threshold to evoke a spreading depression was elevated by more than 2-fold, the frequency of spreading depressions during continuous topical 1 M KCl was reduced by ∼40%, and propagation speed of spreading depression was reduced by ∼15%. This effect developed within 30 minutes after vagus nerve stimulation and persisted for more than 3 hours. Noninvasive transcutaneous vagus nerve stimulation was as efficacious as direct invasive vagus nerve stimulation, and the efficacy did not differ between the ipsilateral and contralateral hemispheres. Our findings provide a potential mechanism by which vagus nerve stimulation may be efficacious in migraine and suggest that susceptibility to spreading depression is a suitable platform to optimize its efficacy.

Roads Less Traveled: Sexual Dimorphism and Mast Cell Contributions to Migraine Pathology

Migraine is a common, little understood, and debilitating disease. It is much more prominent in women than in men (~2/3 are women) but the reasons for female preponderance are not clear. Migraineurs frequently experience severe comorbidities, such as allergies, depression, irritable bowel syndrome, and others; many of the comorbidities are more common in females. Current treatments for migraine are not gender specific, and rarely are migraine and its comorbidities considered and treated by the same specialist. Thus, migraine treatments represent a huge unmet medical need, which will only be addressed with greater understanding of its underlying pathophysiology. We discuss the current knowledge about sex differences in migraine and its comorbidities, and focus on the potential role of mast cells (MCs) in both. Sex-based differences in pain recognition and drug responses, fluid balance, and the blood–brain barrier are recognized but their impact on migraine is not well studied. Furthermore, MCs are well recognized for their prominent role in allergies but much less is known about their contributions to pain pathways in general and migraine specifically. MC-neuron bidirectional communication uniquely positions these cells as potential initiators and/or perpetuators of pain. MCs can secrete nociceptor sensitizing and activating agents, such as serotonin, prostaglandins, histamine, and proteolytic enzymes that can also activate the pain-mediating transient receptor potential vanilloid channels. MCs express receptors for both estrogen and progesterone that induce degranulation upon binding. Furthermore, environmental estrogens, such as Bisphenol A, activate MCs in preclinical models but their impact on pain pathways or migraine is understudied. We hope that this discussion will encourage scientists and physicians alike to bridge the knowledge gaps linking sex, MCs, and migraine to develop better, more comprehensive treatments for migraine patients.

Treatment of chronic migraine with transcutaneous stimulation of the auricular branch of the vagal nerve (auricular t-VNS): a randomized, monocentric clinical trial

Background

Aim of the study was assessment of efficacy and safety of transcutaneous stimulation of the auricular branch of the vagal nerve (t-VNS) in the treatment of chronic migraine.

Methods

A monocentric, randomized, controlled, double-blind study was conducted. After one month of baseline, chronic migraine patients were randomized to receive 25 Hz or 1 Hz stimulation of the sensory vagal area at the left ear by a handhold battery driven stimulator for 4 h/day during 3 months. Headache days per 28 days were compared between baseline and the last month of treatment and the number of days with acute medication was recorded The Headache Impact Test (HIT-6) and the Migraine Disability Assessment (MIDAS) questionnaires were used to assess headache-related disability.

Results

Of 46 randomized patients, 40 finished the study (per protocol). In the per protocol analysis, patients in the 1 Hz group had a significantly larger reduction in headache days per 28 days than patients in the 25 Hz group (−7.0 ± 4.6 vs. −3.3 ± 5.4 days, p = 0.035). 29.4 % of the patients in the 1 Hz group had a ≥50 % reduction in headache days vs. 13.3 % in the 25 Hz group. HIT-6 and MIDAS scores were significantly improved in both groups, without group differences. There were no serious treatment-related adverse events.

Conclusion

Treatment of chronic migraine by t-VNS at 1 Hz was safe and effective. The mean reduction of headache days after 12 weeks of treatment exceeded that reported for other nerve stimulating procedures.

Is there a persistent dysfunction of neurovascular coupling in migraine?

Changes in cerebral blood flow are one of the main features of migraine attack and have inspired the vascular theory of migraine. This traditional view has been reshaped with recent experimental data, which gave rise to the neural theory of migraine. In this review, we speculate that there might be an important link between the two theories, that is, the dysfunction of neurovascular coupling.

Gene expression microarray analysis of the spinal trigeminal nucleus in a rat model of migraine with aura

Cortical spreading depression can trigger migraine with aura and activate the trigeminal vascular system. To examine gene expression profiles in the spinal trigeminal nucleus in rats following cortical spreading depression-induced migraine with aura, a rat model was established by injection of 1 M potassium chloride, which induced cortical spreading depression. DNA microarray analysis revealed that, compared with the control group, the cortical spreading depression group showed seven upregulated genes–myosin heavy chain 1/2, myosin light chain 1, myosin light chain (phosphorylatable, fast skeletal muscle), actin alpha 1, homeobox B8, carbonic anhydrase 3 and an unknown gene. Two genes were downregulated–RGD1563441 and an unknown gene. Real-time quantitative reverse transcription-PCR and bioinformatics analysis indicated that these genes are involved in motility, cell migration, CO₂/nitric oxide homeostasis and signal transduction.

Anesthetic effects on susceptibility to cortical spreading depression

Cortical spreading depression (CSD) is a transient neuronal and glial depolarization and disruption of membrane ionic gradients that propagates slowly across the cerebral cortex. Recent clinical and experimental evidence has implicated CSD in the pathophysiology of migraines and neuronal injury states. In the current study, we examined the influence of four different anesthetics (propofol, dexmedetomidine, isoflurane, pentobarbital) on CSD susceptibility in a KCl application animal model. We found that isoflurane and dexmedetomidine suppressed CSD frequency, and tended to reduce the CSD propagation speed. Our data suggest that these anesthetics may be therapeutically beneficial in preventing CSD in diverse neuronal injury states.

Social anxiety score is high in adolescents with chronic migraine

BACKGROUND

Social anxiety disorder, also known as social phobia, is a marked and persistent fear of one or more social or performance situations in which the person is exposed to unfamiliar people or to possible scrutiny by others. It usually begins in mid-adolescence and has a chronic course and interferes in academic, social, family and personal functioning. Recent studies have shown that social anxiety disorder is more prevalent in adults with migraine. Little evidence on this subject is available for the adolescent population.

METHODS

This study was performed between August 2009 and August 2010; all patients were recruited in schools, pediatric or neuropediatric facilities, and were submitted to a detailed headache questionnaire, which consisted of demographic and clinical data. To evaluate social anxiety, the Social Phobia Inventory was used.

RESULTS

A total of 151 subjects were evaluated: 50 had chronic migraine, 50 had episodic migraine and 51 were control subjects. In the chronic migraine group, the mean score in the Social Phobia Inventory was 18.5 ± 12.4, which was significantly higher than in the episodic migraine group (12.1 ± 8.1) and in the control group (13.8 ± 10.8; F(2131) = 4.8, P= 0.010). The mean score, however, was not significantly different between the control and episodic migraine groups.

CONCLUSIONS

Chronic migraine is strongly associated with high social anxiety score, regardless of demographic data and pain intensity. The total burden of migraine may be increased with social anxiety disorder comorbidity.

Suppressive effect of chronic peroral topiramate on potassium-induced cortical spreading depression in rats

OBJECTIVE

To evaluate the chronic effect of topiramate (TPM) on cortical spreading depression (CSD), which is thought to be related to migraine aura.

METHODS

Male rats (n = 30) were randomized to once-daily peroral treatment with TPM (50, 100, 200 or 600 mg/kg) or vehicle for 6 weeks. We evaluated the characteristics of CSD induced by topical application of KCl under isoflurane anesthesia and the changes in plasma level of TPM in each group. The effect of single administration of TPM on CSD was also evaluated.

RESULTS

After the final administration of TPM, when the plasma level of TPM was high, KCl-induced CSD frequency and CSD propagation velocity were dose-dependently reduced and the interval between CSD episodes was elongated, compared with the vehicle control. However, before the final administration of TPM, when the plasma level was very low, the KCl-induced CSD profile was the same as that in the vehicle control. Single administration of TPM did not alter the CSD profile. Local cerebral blood flow was not significantly altered by chronic administration of TPM.

CONCLUSION

TPM suppressed the frequency and propagation of CSD along the cerebral cortex, and might be a candidate for relief of migraine.

Altered interictal saccadic reaction time in migraine: a cross-sectional study

AIMS

The underlying mechanisms of migraine remain poorly understood, partly because we lack objective methods for quantitative analysis of neurological function. To address this issue, we measured interictal saccadic latency in migraineurs and controls.

METHODS

In a cross-sectional study, we compared interictal saccadic latency distributions of 12,800 saccades in 32 migraineurs with 32 age- and sex-matched controls.

RESULTS

The variability of migraineurs' reaction time distributions was significantly smaller (σ = 1.01 vs. 1.13; p < 0.05) compared with controls. In addition, a smaller proportion of migraineurs generated 'early' saccades (31% vs. 56%: p < 0.05). Sensitivity/specificity analysis demonstrated the potential benefit of this technique to diagnostic discrimination.

CONCLUSIONS

The migraineur's brain behaves significantly differently from that of a control during the interictal period. By analysing whole distributions, rather than just means, data can be related directly to current neurophysiological models: specifically, the observed decrease in variability suggests a functional deficit in the noradrenergic systems influencing the cerebral cortex. From a clinical perspective, this novel method of characterising neurological function in migraine is more rapid, practicable, inexpensive, objective and quantitative than previous methods such as evoked potentials and transcranial magnetic stimulation, and has the potential both to improve current diagnostic discrimination and to help guide future research into the underlying neural mechanisms.

Anxiety disorders in headache patients in a specialised clinic: prevalence and symptoms in comparison to patients in a general neurological clinic

Data from several studies indicate an association of headache with anxiety disorders. In this study, we assessed and differentiated anxiety disorders in 100 headache patients by using the PSWQ (Penn State Worry Questionnaire) screening tool for generalised anxiety disorder (GAD) and the ACQ (Agoraphobic Cognitions Questionnaire) and BSQ (Body Sensation Questionnaire) for panic disorder (PD). Control groups were constructed: (1) on the basis of epidemiological studies on PD and GAD in the general population and (2) by including neurological patients. 37.0% of headache patients had a GAD. 27% of headache patients met the score for PD in the BSQ, 4.0% in the ACQ. Significant results were obtained in comparison to the general population (p < 0.001) and with regard to GAD in comparison with a sample of neurological patients (p < 0.005). The BSQ significantly correlated with the number of medication days (p < 0.005). The results confirm the increased prevalence of GAD in headache patients. PD seems to increase the risk of medication overuse.

Migraine preventive drugs differentially affect cortical spreading depression in rat

Cortical spreading depression (CSD) is the most likely cause of the migraine aura. Drugs with distinct pharmacological properties are effective in the preventive treatment of migraine. To test the hypothesis that their common denominator might be suppression of CSD we studied in rats the effect of three drugs used in migraine prevention: lamotrigine which is selectively effective on the aura but not on the headache, valproate and riboflavin which have a non-selective effect. Rats received for 4 weeks daily intraperitoneal injections of one of the three drugs. For valproate and riboflavin we used saline as control, for lamotrigine its vehicle dimethyl sulfoxide. After treatment, cortical spreading depressions were elicited for 2h by occipital KCl application. We measured CSD frequency, its propagation between a posterior (parieto-occipital) and an anterior (frontal) electrode, and number of Fos-immunoreactive nuclei in frontal cortex. Lamotrigine suppressed CSDs by 37% and 60% at posterior and anterior electrodes. Valproate had no effect on posterior CSDs, but reduced anterior ones by 32% and slowed propagation velocity. Riboflavin had no significant effect at neither recording site. Frontal Fos expression was decreased after lamotrigine and valproate, but not after riboflavin. Serum levels of administered drugs were within the range of those usually effective in patients. Our study shows that preventive anti-migraine drugs have differential effects on CSD. Lamotrigine has a marked suppressive effect which correlates with its rather selective action on the migraine aura. Valproate and riboflavin have no effect on the triggering of CSD, although they are effective in migraine without aura. Taken together, these results are compatible with a causal role of CSD in migraine with aura, but not in migraine without aura.

Patient outcome in migraine prophylaxis: the role of psychopharmacological agents

INTRODUCTION

Migraine is a serious illness that needs correct treatment for acute attacks and, in addition, a treatment prophylaxis, since patients with migraine suffer during acute attacks and also between attacks.

METHODS

A systematic review of the most relevant clinical trials of migraine headache and its epidemiology, pathophysiology, comorbidity, and prophylactic treatment (medical and nonmedical) was carried out using "Medline" and "PsychINFO" from 1973 to 2009. Approximately 110 trials met our inclusion criteria and were included in the current review.

RESULTS

The most effective pharmacological treatment for migraine prophylaxis is propranolol and anticonvulsants such as topiramate, valproic acid, and amitriptyline. Nonmedical treatments such as acupuncture, biofeedback, and melatonin have also been proposed. Peripheral neurostimulation has been suggested for the treatment of chronic daily headache that does not respond to prophylaxis and for the treatment of drug-resistant primary headache. The majority of the pharmacological agents available today have limited efficacy and may cause adverse effects incompatible with long-term use.

LIMITATIONS

The review was limited by the highly variable and often insufficient reporting of the complex outcome data and by the fact that migraine prophylaxis trials typically use headache diaries to monitor the course of the disease. The results of the different studies were also presented in different ways, making comparison of the results difficult.

DISCUSSION

An adequate prophylaxis is crucial in reducing disability and preventing the evolution of the problem into a chronic progressive illness. The implications of the present findings were discussed.

Genetic TPH2 variants and the susceptibility for migraine: association of a TPH2 haplotype with migraine without aura

The serotonergic system plays a major role in the etiology of migraine. The rate-limiting enzyme in serotonin homeostasis and availability is tryptophan hydroxylase (TPH). The TPH2 isoform is responsible for the cerebral serotonin biosynthesis. To investigate the role of genetic variation in TPH2 in the pathogenesis of migraine eight haplotype tagging SNPs covering the whole TPH2 gene where chosen using Haploview and genotyped in 503 migraineurs and 515 healthy controls. Association analysis was performed on a single SNP and haplotype basis using χ² and logistic regression analysis. Single SNP analysis revealed a weak association with migraine, which did not remain after correction for multiple testing. Haplotype analyses revealed association of a haplotype with migraine without aura. Stratification by aura and triptan response did not reveal a positive association with the investigated polymorphisms. These results suggest a possible influence of genetic variation in TPH2 in the pathogenesis of migraine.

Spreading depression: from serendipity to targeted therapy in migraine prophylaxis

Despite the relatively well-characterized headache mechanisms in migraine, upstream events triggering individual attacks are poorly understood. This lack of mechanistic insight has hampered a rational approach to prophylactic drug discovery. Unlike targeted abortive and analgesic interventions, mainstream migraine prophylaxis has been largely based on serendipitous observations (e.g. propranolol) and presumed class effects (e.g. anticonvulsants). Recent studies suggest that spreading depression is the final common pathophysiological target for several established or investigational migraine prophylactic drugs. Building on these observations, spreading depression can now be explored for its predictive utility as a preclinical drug screening paradigm in migraine prophylaxis.

Are Cortical Spreading Depression and Headache in Migraine Causally Linked?

During the past few decades, much controversy has surrounded the pathophysiology of migraine. Cortical spreading depression (CSD) is widely accepted as the neuronal process underlying visual auras. It has been proposed that CSD can also cause the headaches, at least in migraine with aura. We describe three patients, each fulfilling the International Headache Society criteria for migraine with aura, who suffered from headaches 6–10 days per month. Two patients were treated with flunarizine and the third patient with topiramate for the duration of 4 months. All patients reported that aura symptoms resolved completely, whereas the migraine headache attacks persisted or even increased. These observations question the theory that CSD (silent or not) is a prerequisite for migraine headaches.

Is migraine a lateralization defect?

Migraine often co-occurs with patent foramen ovale (PFO), and some people have suggested surgical closure as an efficient treatment for migraine. Prospective studies, however, do not report radical effect of PFO surgery on migraine. Here, we examined the hypothesis that PFO and migraine may cooccur as two independent manifestations of lateralization defect during embryonic development. We measured the absolute displacement of a midline structure, the pineal gland, on brain scans of 39 migraineurs and 26 controls. We found a significant asymmetry of the pineal gland in migraineurs compared with controls. Our data suggest that migraine's circadian component and its association with PFO may be linked to a lateralization defect during embryogenesis, which could be a result from abnormal serotonin regulation.