[Migraine therapy]

Role of endothelial cells in antihyperalgesia induced by a triptan and β-blocker

While blood vessels have long been implicated in diverse pain syndromes (e.g., migraine headache, angina pectoris, vasculitis, and Raynaud's syndrome), underlying mechanisms remain to be elucidated. Recent evidence supports a contribution of the vascular endothelium in endothelin-1-induced hyperalgesia, and its enhancement by repeated mechanical stimulation; a phenomenon referred to as stimulus-induced enhancement of (endothelin) hyperalgesia (SIEH). SIEH is thought to be mediated by release of ATP from endothelial cells, to act on P2X3 receptors on nociceptors. In the present study we evaluated the ability of another vasoactive hyperalgesic agent, epinephrine, to induce endothelial cell-dependent hyperalgesia and SIEH. We found that epinephrine also produces hyperalgesia and SIEH. Both P2X3 receptor antagonists, A317491 and octoxynol-9, which attenuate endothelial cell function, eliminated SIEH without affecting epinephrine hyperalgesia. We further evaluated the hypothesis that members of two important classes of drugs used to treat migraine headache, whose receptors are present in endothelial cells - the triptans and β blockers - have a vascular component to their anti-hyperalgesic action. For this, we tested the effect of ICI-118,551, a β₂-adrenergic receptor antagonist and sumatriptan, an agonist at 5-HT1B and 5-HT₁D receptors, on nociceptive effects of endothelin and epinephrine. ICI-118,551 inhibited endothelin SIEH, and attenuated epinephrine hyperalgesia and SIEH. Sumatriptan inhibited epinephrine SIEH and inhibited endothelin hyperalgesia and SIEH, while having no effect on epinephrine hyperalgesia or the hyperalgesia induced by a prototypical direct-acting inflammatory mediator, prostaglandin E₂. These results support the suggestion that triptans and β-blockers interact with the endothelial cell component of the blood vessel to produce anti-hyperalgesia.

[Cortical spreading depression (CSD): a neurophysiological correlate of migraine aura]

Cortical spreading depression (CSD) is a transient (60-120 s) and at 3-5 mm/min propagating depolarization wave of cortical neurons and glial cells and is characterized by a DC shift of 20-35 mV. It is accompanied by massive redistribution of ions between extracellular and intracellular compartments and by a water influx into the cells. Extracellular potassium ion concentration increases up to 60 mM/l. Potassium ions and the excitatory neurotransmitter glutamate essentially contribute to the initiation and propagation of CSD. Both depolarization and disturbance of brain ion homeostasis regenerate within a few minutes while enhancing energy metabolism, but do not cause damage to normally perfused brain tissue. The similar propagation velocity of CSD and visual scotoma during migraine aura led to the assumption that CSD could be the underlying mechanism of migraine aura. The observation of CSD waves in migraine aura patients with the magnet encephalogram (MEG) technique confirmed this theory. Although many data support the relationship between CSD and aura phase in migraine, the role of CSD in migraine headache is still disputed.

A double-blind, randomized trial of low-dose topiramate vs propranolol in migraine prophylaxis

OBJECTIVE

To assess the efficacy and safety of low-dose topiramate in migraine prophylaxis vs propranolol.

PATIENTS AND METHODS

A randomized, double-blind, clinical trial including 62 patients with frequent migraine headaches (> or = 3 attacks per month) was performed for a period of 8 weeks. The patients were randomly divided into two treatment groups - treated by topiramate 50 mg/day and propranolol 80 mg/day, respectively. The patients were assessed at 0, 4, and 8 weeks of the study. Results - The topiramate group showed a reduction in the mean (+/-SD) of monthly migraine frequency from 6.07 (+/-1.89) to 1.83 (+/-1.39) episodes per month, headache intensity from 7.1 (+/-1.45) to 3.67 (+/-2.1) based on the Visual Analog Scale, and headache duration from 16.37 (+/-7.26) to 6.23 (+/-5.22) hours (P < 0.001). In the patients treated with propranolol, the mean (+/-SD) of monthly headache frequency declined from 5.83 (+/-1.98) to 2.2 (+/-1.67) per month, headache intensity lessened from 6.43 (+/-1.6) to 4.13 (+/-1.94) and headache duration decreased from 15.10 (+/-6.84) to 7.27 (+/-6.46) h (P < 0.001).

CONCLUSION

This study demonstrated that both low-dose topiramate and propranolol could significantly reduce migraine headache frequency, intensity, and duration. However, compared with propranolol, low-dose topiramate showed better results.