Before we apply fMRI to our experimental headache models it is needed to determine how the BOLD response is influenced and changed by the infusion of different drugs such as the NO donor Glyceryl Trinitrate (GTN) and Diamox (acetazolamide). It is known that GTN causes dilation of the cerebral arteries without having any effect on the regional cerebral blood flow. It is not known what effect GTN has on the BOLD response. Diamox (azetazolamide) increases the CBF but it is uncertain what effect the drug has on the BOLD response. Previous studies disagree gravely on this point.