• The primary endpoints were the difference between the area under the curve of the MCA area and the difference between the area under the curve of the diameter of the MCA on an active day and on a placebo day recorded over 60 mins.
  

• The secondary endpoints were difference in the area under the curve for the relative changes in area in percent deviation from baseline, and the difference in headache response.
  

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).