Adrenergic supersensitivity of the pupil in idiopathic headache.

In idiopathic headache (IH) sufferers, phenylephrine and fenfluramine induce a pupillary dilatation respectively greater and lesser than in controls. The difference may be due to a supersensitivity of the iris alpha adrenoceptors caused by a deficiency of noradrenaline in the iris adrenergic nerve terminal of the IH sufferer. These findings seem to support the hypothesis of a brain receptorial, monoamine supersensitivity in IH.