INTRODUCTION: For many years, scientists have debated the possibility that an individual "migraine threshold" determines the likelihood with which individuals may express migraine attacks.

DISCUSSION: Recent discoveries provided evidence for both genetic and environmental influences on individual migraine expression. The question is whether any person may express a migraine attack given a sufficiently strong stimulus or provocation. Here, we reviewed and discussed the ability of nitric oxide to induce migraine-like attacks in normal individuals.

CONCLUSION: Experimental data show that normal individuals may develop a migraine-like attack and that the human data point to different ways of further developing existing animal and human models.