To examine the ability of MRA to measure the effect of GTN on the intra-cranial vascular response during the GTN-induced headache in healthy volunteers.

The only intra cranial structures innervated by sensory nerves, and therefore a possible source of the headpain are the meninges and the large intracerebral arteries. The dilatation of the cerebral vessels may not be the origin of the head pain per se, but measurements of the intra cerebral vascular bed in the past has proven valuable in the migraine-research, and has helped elucidate the basis for the migraine aura (Olesen, Friberg et al. 1990). The effects of different signal molecules on the intra cerebral vasculature continue to be an important field in the migraine research, in the search for possible pain causing signaling molecules.

Therefore we have set up at study to examine if MR-Angiography (MRA) can be used for monitoring of the vascular response after challenge with the known vasodilator GTN. This drug was chosen because it is well characterized and a large body of evidence from earlier studies could serve as background data (Thomsen 1997).

Inclusion Criteria:

• healthy volunteers

Exclusion Criteria:

• history of migraine or any other type of primary headaches; any kind of daily medication (including prophylactic headache therapy but not oral contraceptives); excessive use of analgesics (corresponding to >2 g aspirin/day), pregnancy and all known contraindications for MR-examinations incl. claustrophobia.