To develop a pragmatic migraine model the investigators will induce headache in healthy volunteers with a phosphodiesterase inhibitor (cilostazol). The participants will be pre-treated with sumatriptan. If the headache responds to sumatriptan, the model can be used to test new drug candidates.

There remains a great need for more effective anti-migraine drugs with fewer side effects. Human experimental models are valuable in early phase development of new anti-migraine drugs but useful models have not yet been developed. The investigators' group has shown that Cilostazol, a phosphodiesterase inhibitor induce headache/migraine in both healthy volunteers and in patients with migraine without aura (MO).

To validate cilostazol as a model, the headache must respond to specific migraine treatment with sumatriptan.

Hypothesis: Cilostazol induces a migraine-like headache in healthy subjects. The induced headache can be pre-treated with a specific anti-migraine drug; sumatriptan.

Aim: Developing a pragmatic and valid model for the testing of new anti-migraine drugs.

Inclusion Criteria:

Healthy subjects of both sexes Age 18-60 years Weight 50-95 kg. Females were requested to use effective contraception.

Exclusion Criteria:

Any type of headache (except episodic tension-type headache < 1 day per week) Serious somatic or psychiatric disease Pregnancy Intake of daily medication (except oral contraceptives).