[Histamine-release and migraine]

Calcitonin gene-related peptide in migraine: intersection of peripheral inflammation and central modulation

Over the past two decades, a convergence of basic and clinical evidence has established the neuropeptide calcitonin-gene-related peptide (CGRP) as a key player in migraine. Although CGRP is a recognised neuromodulator of nociception, its mechanism of action in migraine remains elusive. In this review, we present evidence that led us to propose that CGRP is well poised to enhance neurotransmission in migraine by both peripheral and central mechanisms. In the periphery, it is thought that local release of CGRP from the nerve endings of meningeal nociceptors following their initial activation by cortical spreading depression is critical for the induction of vasodilation, plasma protein extravasation, neurogenic inflammation and the consequential sensitisation of meningeal nociceptors. Mechanistically, we propose that CGRP release can give rise to a positive-feedback loop involved in localised increased synthesis and release of CGRP from neurons and a CGRP-like peptide called procalcitonin from trigeminal ganglion glia. Within the brain, the wide distribution of CGRP and CGRP receptors provides numerous possible targets for CGRP to act as a neuromodulator.

Prevalence of migraine headaches in patients with allergic rhinitis

BACKGROUND

Histamine has been implicated in the pathogenesis of migraine headaches. Because allergic rhinitis (AR) is a histamine-driven syndrome and the nasal passage is in close proximity to the central nervous system, we hypothesize that AR may trigger migraine headaches.

OBJECTIVE

To determine the prevalence of migraine headaches in patients with and without AR.

METHODS

Allergic rhinitis was diagnosed based on skin or radioallergosorbent test results, clinical history, and physical examination findings. The diagnosis of migraine headache was made if patients fulfilled the International Headache Society criteria. Surveys were obtained from hospital-based allergy, pediatric, and internal medicine clinics, all serving the same inner-city population.

RESULTS

A total of 294 surveys were completed. Of 76 patients in the AR group, 26 (34%) had headaches meeting the International Headache Society criteria for migraines, and of the 57 patients in the non-AR group, only 2 (4%) had headaches that met the criteria. A Fisher exact test showed P = 8.2 x 10(-6). The odds ratio was 14.3, which signifies that the odds of having migraine headaches is 14.3 times higher in the AR group than in the non-AR group.

CONCLUSIONS

There is a high prevalence of migraine headaches in patients with AR compared with those without AR. We propose that histamine plays a key role in triggering migraines by means of vasodilation and inflammation in the pathogenesis of migraine headaches.