Neurovascular pharmacology of migraine

Migraine neuroscience: from experimental models to target therapy

Migraine sciences have witnessed tremendous advances in recent years. Pre-clinical and clinical experimental models have contributed significantly to provide useful insights into the brain structures that mediate migraine attacks. These models have contributed to elucidate the role of neurotransmission pathways and to identify the role of important molecules within the complex network involved in migraine pathogenesis. The contribution and efforts of several research groups from all over the world has ultimately lead to the generation of novel therapeutic approaches, specifically targeted for the prevention of migraine attacks, the monoclonal antibodies directed against calcitonin gene-related peptide or its receptor. These drugs have been validated in randomized placebo-controlled trials and are now ready to improve the lives of a large multitude of migraine sufferers. Others are in the pipeline and will soon be available.

Fetal Cerebrovascular Maturation: Effects of Hypoxia

The human cerebral vasculature originates in the fourth week of gestation and continues to expand and diversify well into the first few years of postnatal life. A key feature of this growth is smooth muscle differentiation, whereby smooth muscle cells within cerebral arteries transform from migratory to proliferative to synthetic and finally to contractile phenotypes. These phenotypic transformations can be reversed by pathophysiological perturbations such as hypoxia, which causes loss of contractile capacity in immature cerebral arteries. In turn, loss of contractility affects all whole-brain cerebrovascular responses, including those involved in flow-metabolism coupling, vasodilatory responses to acute hypoxia and hypercapnia, cerebral autoregulation, and reactivity to activation of perivascular nerves. Future strategies to minimize cerebral injury following hypoxia-ischemic insults in the immature brain might benefit by targeting treatments to preserve and promote contractile differentiation in the fetal cerebrovasculature. This could potentially be achieved through inhibition of receptor tyrosine kinase-mediated growth factors, such as vascular endothelial growth factor and platelet-derived growth factor, which are mobilized by hypoxic and ischemic injury and which facilitate contractile dedifferentiation. Interruption of the effects of other vascular mitogens, such as endothelin and angiotensin-II, and even some miRNA species, also could be beneficial. Future experimental work that addresses these possibilities offers promise to improve current clinical management of neonates who have suffered and survived hypoxic, ischemic, asphyxic, or inflammatory cerebrovascular insults.

Acupuncture for Frequent Migraine: A Randomized, Patient/Assessor Blinded, Controlled Trial with One-Year Follow-Up

Objectives. This study aimed to evaluate the efficacy and safety of manual acupuncture as a prophylaxis for frequent migraine. Methods. Fifty frequent migraineurs were randomly allocated to receive 16 sessions of either real acupuncture (RA = 26) or sham acupuncture (SA = 24) during 20 weeks. The primary outcomes were days with migraine over four weeks, duration, and intensity of migraine and the number of responders with more than 50% reduction of migraine days. The secondary outcomes were the relief medication, quality of migraine, quality of life, and pressure pain thresholds. Results. The two groups were comparable at baseline. At the end of the treatment, when compared with the SA group, the RA group reported significant less migraine days (RA: 5.2 ± 5.0; SA: 10.1 ± 7.1; P = 0.008), less severe migraine (RA: 2.18 ± 1.05; SA: 2.93 ± 0.61; P = 0.004), more responders (RA: 19 versus SA: 7), and increased pressure pain thresholds. No other group difference was found. Group differences were maintained at the end of the three-month follow-up, but not at the one-year follow-up. No severe adverse event was reported. Blinding was successful. Discussion. Manual acupuncture was an effective and safe treatment for short-term relief of frequent migraine in adults. Larger trials are warranted.

Sublingual Delivery of Frovatriptan: An Indication of Potential Alternative Route

Frovatriptan, a 5-HT1B and 5-HT1D receptor agonist, is used for the treatment of acute migraine attack. This molecule is classified into second line therapy because of its slow onset of action (peak response obtained after 4 hours of administration) and low bioavailability (25%). Moreover, its therapy is the most costly among all triptans. Attempt has been made in present work to suggest a way out to fasten its onset of action and to enhance its bioavailability. Prepared tablets were evaluated by physicochemical tests, in vitro permeation studies, ex vivo permeation studies, and histopathological studies. Suitable mathematical calculations were performed to calculate the minimum amount of bioavailability that could be enhanced. Tablets containing chitosan (5% w/w) were found to give optimum results. Prepared tablets can double the bioavailability of frovatriptan and can initiate its response within 10 minutes of its administration. Suggestive alternative has the potential to increase the efficacy of frovatriptan for treating acute migraine attack.

Capsaicin-induced vasodilatation in human nasal vasculature is mediated by modulation of cyclooxygenase-2 activity and abrogated by sulprostone

Extensively based on evidence gained from experimental animal models, the transient receptor potential vanilloid receptor type 1 (TRPV1)-activator capsaicin is regarded as a valuable tool in the research on neurogenic inflammation. Although capsaicin-related drugs gained renewed interest as a therapeutic tool, there is also controversy as whether neurogenic inflammation actually takes place in humans. In this study, we verified the involvement of capsaicin in vascular responses that are regarded to be implicated in the cascade of neurogenic inflammatory mechanisms. By means of ex vivo functional experiments on human nasal mucosal vascular beds, the effect and mechanism of action of capsaicin was assessed in the absence and presence of various agents that interfere with potentially related transduction pathways. Ten micromolars of capsaicin induced vasodilatations that were reduced by the selective EP(1) prostanoid receptor antagonist SC19220 (10 μM) and almost abolished by the selective COX-2 inhibitor NS398 (1 μM) and the EP(1/3) receptor agonist sulprostone (0.1-10 nM), but not affected by the TRPV1-antagonists capsazepine (5 μM), the neurokinin NK(1) receptor antagonist GR20517A (1 μM), and the calcitonin-gene-related peptide (CGRP) receptor antagonist CGRP8-37 (100 nM). Spontaneously released PGE(2) and PGD(2) levels were significantly reduced in the presence of capsaicin. In conclusion, capsaicin-at concentrations clinically applied or under investigation for diverse disease backgrounds-induces a vasodilatory response in human nasal mucosa via a mechanism involving TRPV1-independent reduction of PGE(2) production by modulation of COX-2 enzymatic activity. These vasodilatations can be suppressed by the EP(1/3) receptor agonist sulprostone at subnanomolar concentrations.

Neurovascular compression of the greater occipital nerve: implications for migraine headaches

BACKGROUND

Surgical release of the greater occipital nerve has been demonstrated to be clinically effective in eliminating or reducing chronic migraine symptoms. However, migraine symptoms in some patients continue after this procedure. It was theorized that a different relationship between the greater occipital nerve and occipital artery may exist in these patients that may be contributing to these outcomes. A cadaveric investigation was performed in an effort to further delineate the occipital artery-greater occipital nerve relationship.

METHODS

Fifty sides of 25 fresh cadaveric posterior necks and scalps were dissected. The greater occipital nerve was identified within the subcutaneous tissue and its relationship with the occipital artery was delineated. A topographic map of the intersection of the two structures was created.

RESULTS

The greater occipital nerve and occipital artery have an intimate relationship, and crossed each other in 27 hemiheads (54.0 percent). The relationship between these structures when they crossed varied from a single intersection to a helical intertwining.

CONCLUSIONS

The greater occipital nerve and occipital artery have an anatomical intersection 54 percent of the time. There are two morphologic types of relationships between the structures: a single intersection point and a helical intertwining. Vascular pulsation may cause irritation of the nerve and is a possible explanation for migraine headaches that have the occipital region as a trigger point. Future imaging studies and clinical investigation is necessary to further examine the link between anatomy and clinical presentation.