Dilation and inflammation of cephalic arteries and intracranial extra cerebral arteries cause the migraine headache. The migraine-associated symptoms result from the activation of the sympathetic nervous system caused by the pain. The migraine aura is caused by the neurophysiological phenomenon of spreading excitation/depression. The various mechanisms are tied together in the so-called "parallel theory" of the pathogenesis of the migraine attack. The abortive antimigraine medications act by constricting the dilated arteries through stimulation of the serotonin 1B receptor. The preventive antimigraine medications act by increasing the tone of the extacranial arteries, inhibiting the mechanism of neurogenic inflammation, or inhibiting pain transmission within the central nervous system.