Neurogenic vasodilation of dural blood vessels is not mediated by cholinergic transmission in the anaesthetised rat

Macroscopic Innervation of the Dura Mater Covering the Middle Cranial Fossa in Humans Correlated to Neurovascular Headache

The trigeminovascular system within the cranial dura mater is a possible cause of headaches. The aim of this study is to investigate macroscopically dural innervation around the middle meningeal artery (MMA) in the middle cranial fossa. Forty-four sides of the cranial dura overlying the skull base obtained from 24 human cadavers were stained using Sihler’s method. Overall, the nervus spinosus (NS) from either the maxillary or mandibular trigeminal divisions ran along the lateral wall of the middle meningeal vein rather than that of the MMA. Distinct bundles of the NS running along the course of the frontal branches of the MMA were present in 81.8% of cases (N = 36). Others did not form dominant nerve bundles, instead giving off free nerve endings along the course of the MMA or dural connective tissue. The distribution of these nerve endings was similar to that of the course of the frontal, parietal and petrosal branches of the MMA (11.4%). The others were not restricted to a perivascular plexus, crossing the dural connective tissues far from the MMA (6.8%). These findings indicate that the NS generally travels alongside the course of the frontal branches of the MMA and terminates in the vicinity of the pterion.

Comparison of the vasodilator responses of isolated human and rat middle meningeal arteries to migraine related compounds

Background

Migraine attacks occur spontaneously in those who suffer from the condition, but migraine-like attacks can also be induced artificially by a number of substances. Previously published evidence makes the meninges a likely source of migraine related pain. This article investigates the effect of several vasodilators on meningeal arteries in order to find a connection between the effect of a substance on a meningeal vessel and its ability to artificially induce migraine.

Methods

A myograph setup was used to test the vasodilator properties of the substances acetylcholine (ACh), sodium nitroprusside (SNP), sildenafil, prostaglandin E₂ (PGE₂), pituitary adenylate cyclase activating peptide-38 (PACAP-38), calcitonin gene-related peptide (CGRP) and NaCl buffer on meningeal arteries from human and rat. An unpaired t-test was used to statistically compare the mean E_max(%) at the highest concentration of each substance to the E_max(%) of NaCl buffer.

Results

In the human experiments, all substances except PACAP-38 had an E_max (%) higher than the NaCl buffer, but the difference was only significant for SNP and CGRP. For the human samples, clinically tested antimigraine compounds (sumatriptan, telcagepant) were applied to the isolated arteries, and both induced a significant decrease of the effect of exogenously administrated CGRP. In experiments on rat middle meningeal arteries, pre-contracted with PGF_2α, similar tendencies were seen. When the pre-contraction was switched to K⁺ in a separate series of experiments, CGRP and sildenafil significantly relaxed the arteries.

Conclusions

Still no definite answer can be given as to why pain is experienced during an attack of migraine. No clear correlation was found between the efficacy of a substance as a meningeal artery vasodilator in human and the ability to artificially induce migraine or the mechanism of action. Vasodilatation could be an essential trigger, but only in conjunction with other unknown factors. The vasculature of the meninges likely contributes to the propagation of the migrainal cascade of symptoms, but more research is needed before any conclusions can be drawn about the nature of this contribution.

Headache after exposure to ‘date-rape’ drugs

Summary

We report two patients who developed a prolonged featureless headache, they think after a drink was ‘spiked’. We speculate that each was exposed to scopolamine, resulting in enhanced trigeminal release of vasodilator neuropeptides, including Calcitonin Gene-Related Peptide (CGRP), and thus the headache.

A trans-cultural comparison of the organisation of care at headache centres world-wide

Background: The need to provide better outcomes for patients with headache, and to minimise the costs involved in doing so, has prompted the search for new modes of service delivery by exploring the service organisation and nursing role from various cultural, economic and global perspectives.

Materials and Methods: This study was based on comparisons with the UK headache service up to 2007, the point at which this study was set up. This UK service was based at the National Hospital for Neurology and Neurosurgery (NHNN, UCLH Trust). Data were obtained from US headache centres in 2008 and from centres in Copenhagen, Bangkok, Sydney and Porto Alegre in 2009.

Results: A comparison shows the key components of services at all centres showing the team structure and size of service. Prominent features at the centres included: team-working, regular meetings, educational input, good access and communication among team members, headache-trained neurologists, specialist nursing at most centres, and the input of psychological and physical therapists at some centres.

Conclusions: The problems of tertiary headache care are very similar throughout the world and seem to transcend ethnic, cultural and economic considerations.

Measurement of meningeal blood vessel diameter in vivo with a plug-in for ImageJ

Changes in blood vessel diameter can be measured manually, but this is time-consuming and often impractical. For automatic measurement commercial solutions are available, but the proprietary algorithms and their potential shortcomings are not known to the user. We present an approach with a CCD camera for image acquisition combined with free and open source ImageJ software for offline analysis. A subtraction image allows for the evaluation of the diameter changes throughout the field of view. A full width at half-maximum algorithm plug-in was written to measure the vessel diameter. For a given line across a vessel, the results of five measurements with parallel shifts throughout an image stack are copied to the clipboard. For validation of this method an established in vivo model was used, namely vascular changes in the rat dura mater, reflecting the activity of the afferent neurons. Vasoconstriction of the meningeal arterioles induced by local electrical stimulation of the dura was inhibited by intravenous administration of the adrenoceptor antagonist phentolamine and amplified by the CGRP receptor antagonist olcegepant. The described methods allow the user to quickly evaluate vessel diameter changes in the whole acquired field at any selected position.

Finding New Drug Targets for the Treatment of Migraine Attacks

No new preventive drugs specific to migraine have appeared for the last 20 years and existing acute therapies need improvement. Unfortunately, no animal models can predict the efficacy of new therapies for migraine. Because migraine attacks are fully reversible and can be aborted by therapy, the headache- or migraine-provoking property of naturally occurring signalling molecules can be tested in a human model. This model has predicted efficacy of nitric oxide synthase inhibition and calcitonin gene-related peptide receptor blockade. The pharmaceutical industry should pay more attention to human models, although methods are different from normal target validation.

Carbachol induces headache, but not migraine-like attacks, in patients with migraine without aura

Carbachol induces headache in healthy subjects, but the migraine eliciting effect of carbachol has not previously been studied. We hypothesized that the cholinomimetic agonist carbachol would induce headache and migraine-like attacks in migraineurs. Carbachol (3 µg/kg) or placebo was randomly infused into 18 patients with migraine without aura in a double-blind crossover study. Headache was scored on a verbal rating scale from 0 to 10. Velocity in the middle cerebral artery (VMCA) and diameter of the superficial temporal artery (STA) were recorded. Fifteen patients experienced headache after carbachol compared with eight after placebo ( P = 0.039). There was no difference in incidence of migraine-like attacks after carbachol ( n = 8) compared with placebo ( n = 6) ( P = 0.687). Carbachol caused a decrease in VMCA ( P = 0.044), but no change in STA ( P = 0.089) compared with placebo. The study demonstrated that carbachol provocation is not a good model for experimental migraine.

Scopolamine-induced migraine like headache

OBJECTIVE

Scopolamine butylbromide (SB), a muscarinic receptor antagonist, is used commonly in gastric X-ray examination in the physical check-up in Japan. This study describes clinical features of SB-induced headache.

PATIENTS AND METHODS

SB-induced headache was defined as headache that started within 20 minutes after intramuscular administration of SB (20 mg/body). The Primary and the secondary headaches were diagnosed according to the ICHD-II criteria. SB-induced headache was classified as headache induced by acute substance use or that due to exposure (ICHD-II code 8.1). Clinical features and background of subjects with SB-induced headache were analyzed. We also estimated the frequency of SB-related headache between migraineurs and non-migraineurs.

RESULTS

A total of 54 subjects (39 women and 15 men) experienced SB-induced headache. All subjects had the present history of migraine. Nine subjects had > or =2 times of the headache. Mean age (SD) was 46.2 (9.7) years [46.2 (9.7) for women and 46.3 (10.0) for men]. Clinical hallmarks of headache showed that pulsating / throbbing pain occurred in diffuse or bilateral head sites. Headache worsened at 20-30 minutes from the onset and persisted for 6-18 hours, and ameliorated gradually 8 hours later. All subjects had repeated nausea and vomiting. Severity of headache revealed severe degree requiring complete bed rest in 50 subjects (92.6%). SB-induced headache had similar characteristics as migraine without aura (MO) attacks. Liver and renal functions were normal in all SB-related migraineurs. They had no allergic history of medication and food. In 1,865 non-migraine controls, one healthy subject had a mild degree of migraine like headache triggered by SB injection.

CONCLUSION

SB triggers a severe degree MO like headache or worsens pre-existing migraine in some migraineurs. SB-induced headache could contribute to disequilibrium between acetylcholine and other neuropeptides. We should use SB more carefully as it can be an aggravating drug of migraine.

Temperature-dependent neuronal regulation of arterial blood flow in rat cranial dura mater

Several endogenous factors such as calcitonin gene-related peptide (CGRP), nitric oxide, and histamine have been found to affect meningeal blood flow. A possible regulation of meningeal blood flow by thermosensitive neurons has not been examined so far. We monitored meningeal arterial blood flow with laser Doppler flowmetry in anesthetized rats. A vortex thermode was used to control the temperature of the exposed dura mater. After fast heating from 36 degrees C to 45 degrees C, meningeal blood flow increased slowly within 5 min. Immediately after fast cooling to 36 degrees C, the flow transiently increased before it returned to the initial basal level. After the application of lidocaine onto the dura mater, the heating-induced flow increase was greater and the transient cooling-induced flow increase was reduced, indicating the involvement of neuronal mechanisms. Furthermore, after topical application of phenylephrine, the cooling-induced response was increased, and following topical application of phentolamine the heating-induced flow increase was higher. The flow changes evoked by thermal stimulation were unaffected by high concentrations of 1) cimetidine, 2) a vasoactive intestinal polypeptide antagonist and the CGRP receptor antagonists, 3) CGRP(8-37), and 4) BIBN4096BS. We conclude that activation of temperature-sensitive meningeal afferents can regulate the dura mater blood flow by a sympathetic reflex.

Effect of two novel CGRP-binding compounds in a closed cranial window rat model

We investigated the in vivo effects of two novel calcitonin gene-related peptide (CGRP) binding molecules in the genuine closed cranial window model in the rat. The RNA-Spiegelmer (NOX-C89) and the monoclonal CGRP antibody are CGRP scavengers and might be used as an alternative to CGRP-receptor antagonists in the treatment of migraine. Rats were anaesthetized and a closed cranial window established. Changes in dural and pial artery diameter and mean arterial blood pressure were measured simultaneously. Infusion of the RNA-Spiegelmer or the CGRP antibody alone had no effect on the arteries or the mean arterial blood pressure. We then used a bolus of 0.3 microg/kg CGRP (n=6) or electrical stimulation (25 V, 5 Hz, 1 ms pulse width and of 10 s of duration) (n=6) to induce dilatation of dural and pial arteries (mediated via CGRP-receptors). Pre-treatment with the RNA-Spiegelmer inhibited CGRP-induced vasodilatation of the dural artery (from 38+/-17% to 7+/-3%) and the pial artery (from 14+/-1% to 3+/-2%) (P<0.05). The RNA-Spiegelmer, however, did not significantly inhibit dilatation induced by electrical stimulation (P>0.05). The CGRP antibody caused a significant reduction of the dural artery diameter caused by intravenous CGRP-infusion (from 23+/-5% to 12+/-3%) (P<0.05), but did not inhibit dilatation caused by electrical stimulation (P>0.05). In conclusion, the CGRP scavengers effectively inhibited the effect of circulating CGRP but do not modify the effect of electrical stimulation and the consequent liberation of CGRP from perivascular sensory nerve fibres.

Effects of oestrogen on trigeminal ganglia in culture: implications for hormonal effects on migraine

Although migraine is more common in women than men and often linked to the menstrual cycle, few studies have investigated the biological basis of hormonal influences on the trigeminovascular system. In the present study we investigated the effect of physiological levels (10(-9) m) oestrogen on female rat trigeminal ganglia in vitro. Immunocytochemical analysis demonstrated the presence of oestrogen receptor-alpha in a predominantly cytoplasmic location and in neurites. Microarray analysis demonstrated that oestrogen treatment regulates several genes with potential relevance to menstrual migraine. The genes that were upregulated included synapsin-2, endothelin receptor type B, activity and neurotransmitter-induced early gene 7 (ania-7), phosphoserine aminotransferase, MHC-1b, and ERK-1. Down-regulated genes included IL-R1, bradykinin B2 receptor, N-tropomodulin, CCL20, GABA transporter protein, fetal intestinal lactase-phlorizin hydrolase, carcinoembryonic antigen-related protein, zinc finger protein 36, epsin 1 and cysteine string protein. Protein activity assays demonstrated that exposure of the cultured neurons to oestrogen leads to activation of ERK, which has been linked to inflammatory pain. Immunocytochemistry demonstrated that activated ERK was present in neurons containing peripherin, a marker of nociceptive neurons. Several of the genes in the present study may provide potential targets for understanding the association of oestrogen with migraine and other hormone-related orofacial pain.

The role of CGRP and nicotinic receptors in centrally evoked facial blood flow changes

The release of CGRP in humans is associated with the occurrence of migraine headaches. The vasoactive neuropeptide is released by afferent neurones originating in the peripherally located trigeminal ganglion supplying the dura mater. The role of CGRP in migraine is further supported by recently released data showing that the CGRP-antagonist BIBN4096BS is clinically effective for the treatment of migraine headaches. Yet, the trigger for CGRP release during migraine attacks is not identified. It is suggested that the peripheral CGRP release during a migraine attack might be either triggered by direct activation of afferent dural neurones, or, by indirect activation via the central nervous system. Recently, we were able to show that the CGRP-antagonist BIBN4096BS is able to inhibit vasodilation induced by trigeminal ganglion stimulation. Now, we extend our studies to the investigation of facial blood flow changes induced by electrical stimulation of the brainstem trigeminal nucleus caudalis (TNC). Here, we show that stimulation of the TNC leads to a pronounced increase of facial blood flow. The nicotinic antagonist Hexamethonium reduced the evoked flow by approximately 50% (30 mg/kg), while the muscarinic antagonist Atropin did not influence the stimulation evoked blood flow. Application of BIBN4096BS (0.3 mg/kg, i.v.) diminished the evoked flow almost completely. Therefore, we conclude that CGRP represents the key player in TNC-induced facial vasodilation, while activation of nicotinic receptors modulates centrally induced peripheral neurogenic vasodilation.

Calcitonin Gene-Related Peptide Antagonists as Treatments of Migraine and Other Primary Headaches

Calcitonin gene-related peptide (CGRP) is a potent neuromodulator that is expressed in the trigeminovascular system and is released into the cranial circulation in various primary headaches. CGRP is released in migraine, cluster headache and paroxysmal hemicrania. The blockade of its release is associated with the successful treatment of acute migraine and cluster headache. CGRP receptor blockade has recently been shown to be an effective acute anti-migraine strategy and is non-vasoconstricting in terms of the mechanism of action. The prospect of a non-vasoconstricting therapy for acute migraine offers a real opportunity to patients, and perhaps more importantly, provides a therapeutic rationale to reinforce migraine as a neurological disorder.