One hundred years of migraine research: major clinical and scientific observations from 1910 to 2010

Efficacy, end points and eventualities: sumatriptan/naproxen versus butalbital/paracetamol/caffeine in the treatment of migraine

Migraine is a widespread, relapsing, remittent syndrome. No animal model predicts whether test medications will be clinically useful. Using a modern, well-controlled, sophisticated study design, Derosier et al. demonstrates not only that a butalbital formulation has modest efficacy as an acute treatment for migraine but also that a sumatriptan-naproxen combination is superior. These conclusions are reached using a variety of internally consistent secondary efficacy end points. The primary end point chosen (highly conservative and fashionable in some academic circles) was a technical failure (and not a negative experimental finding). Migraine is intrinsically pleiomorphic: diverse treatment options help match patient with therapy. This study does not justify blanket bans on (admittedly hazardous) barbiturate therapies, and regulators should not impose end point conservatism to an extent that will stifle further progress.

Functional selectivity in GPCR heterocomplexes

G protein-coupled receptors (GPCRs) can couple to more than one signaling pathway. Biophysical studies and pharmacological theory indicate that they exist in different active conformations that differ in their capacity to activate specific signaling pathways. Individual agonists stabilize particular active conformations and thereby can differ in their relative activation of different signaling pathways coupled to the same receptor, a phenomenon referred to as functional selectivity. Many pairs of GPCRs have been shown to interact and form heterocomplexes in vitro and in vivo. Recent studies implicate these complexes in the responses to some therapeutic drugs and drugs of abuse, and raise the possibility that they may be involved in mediating functional selectivity.

Sumatriptan inhibition of N-type calcium channel mediated signaling in dural CGRP terminal fibres

The selective 5-HT₁ receptor agonist sumatriptan is an effective therapeutic for migraine pain yet the antimigraine mechanisms of action remain controversial. Pain-responsive fibres containing calcitonin gene-related peptide (CGRP) densely innervating the cranial dura mater are widely believed to be an essential anatomical substrate for the development of migraine pain. 5-HT₁ receptors in the dura colocalize with CGRP fibres in high density and thus provide a possible peripheral site of action for sumatriptan. In the present study, we used high-resolution optical imaging selectively within individual mouse dural CGRP nociceptive fibre terminations and found that application of sumatriptan caused a rapid, reversible dose-dependent inhibition in the amplitude of single action potential evoked Ca²⁺ transients. Pre-application of the 5-HT₁ antagonist GR 127935 or the selective 5-HT(1D) antagonist BRL 15572 prevented inhibition while the selective 5-HT(1B) antagonist SB 224289 did not, suggesting this effect was mediated selectively through the 5-HT(1D) receptor subtype. Sumatriptan inhibition of the action potential evoked Ca²⁺ signaling was mediated selectively through N-type Ca²⁺ channels. Although the T-type Ca²⁺ channel accounted for a greater proportion of the Ca²⁺ signal it did not mediate any of the sumatriptan inhibition. Our findings support a peripheral site of action for sumatriptan in inhibiting the activity of dural pain fibres selectively through a single Ca²⁺ channel subtype. This finding adds to our understanding of the mechanisms that underlie the clinical effectiveness of 5-HT₁ receptor agonists such as sumatriptan and may provide insight for the development of novel peripherally targeted therapeutics for mitigating the pain of migraine.

Effects of LPS on P2X3 receptors of trigeminal sensory neurons and macrophages from mice expressing the R192Q Cacna1a gene mutation of familial hemiplegic migraine-1

A knockin (KI) mouse model with the R192Q missense mutation in the Cacna1a gene commonly detected in familial hemiplegic migraine was used to study whether trigeminal ganglia showed a basal inflammatory profile that could be further enhanced by the lipopolysaccharide (LPS) toxin. Adenosine-5'-triphosphate (ATP)-gated purinergic ionotropic receptor 3 (P2X3) currents expressed by the large majority of trigeminal sensory neurons were taken as functional readout. Cultured R192Q KI trigeminal ganglia showed higher number of active macrophages, basal release of tumor necrosis factor alpha (TNFα), and larger P2X3 receptor currents with respect to wild type (WT) cells. After 5 h application of LPS in vitro, both WT and R192Q KI cultures demonstrated significant increase in macrophage activation, very large rise in TNFα mRNA content, and ambient protein levels together with fall in TNFα precursor, suggesting potent release of this inflammatory mediator. Notwithstanding the unchanged expression of P2X3 receptor protein in WT or R192Q KI cultures, LPS evoked a large rise in WT neuronal currents that recovered faster from desensitization. Basal R192Q KI currents were larger than WT ones and could not be further augmented by LPS. These data suggest that KI cultures had a basal neuroinflammatory profile that might facilitate the release of endogenous mediators (including ATP) to activate constitutively hyperfunctional P2X3 receptors and amplify nociceptive signaling by trigeminal sensory neurons.

The enigma of the dorsolateral pons as a migraine generator

In this editorial, we integrate improved understanding of functional and structural brain stem anatomy with lessons learned from other disciplines on brainstem function to provide an alternative interpretation to the data used to support the brainstem migraine generator theory.

The history of oxygen inhalation as a treatment for cluster headache

OVERVIEW

Oxygen has been a generally accepted treatment method for cluster headache attacks ever since Kudrow (1981) conducted a controlled trial showing that oxygen was equally or even more effective than ergotamine injections.

PURPOSE

The aim of the present study was to provide a historical perspective of oxygen treatment in cluster headache and to find the origin of this treatment. Oxygen for cluster headache was first described by Horton in 1952 and for migraine patients in 1940 by Alvarez. At the time, neither of the authors provided any reason why they chose for this treatment method. The vasoconstrictive effect of oxygen was not described by Horton until 1961.

CONCLUSION

We suggest that these authors originally adhered to the vasoconstrictive theory of vascular headache that was prevalent in the early 20th century until Wolff demonstrated the contrary in the late 1930s. The early literature describes an analogy between angina pectoris and migraine, as both being due to vasoconstriction. As oxygen was described as a treatment for angina pectoris, this may be the reason why oxygen was tried for migraine and cluster headache at a time when they were not recognized as separate entities. Later it turned out to be more effective for cluster headache.