Posted by Ueli (195.162.170.2) on September 24, 2000 at 22:16:47:
In Reply to: Vasoconstrictors posted by Bob P on September 23, 2000 at 22:27:22:
In my understanding:
Both Ca channel blockers and ACE inhibitors, in the case they are used against high BP, relax the somehow cramped-up smooth muscles around the blood vessels. In doing so, the blood flows more freely, thus a lower (blood) pressure is sufficient to achieve the same flow rate.
The same two meds, in an otherwise healthy clusterhead, make these muscles to react slower and less violent to chemical or nerve stimuli. At the start of a CH attack, some artery in our head starts to expand and through some (faulty) positive feedback expands very rapidly, hence the steep raise in cluster pain. The preventive use of these meds makes the vessels expand slower, so damping (or even breaking) the positive feedback.
If prevention did not work (or is not used) then abortive vasoconstrictors may help: Sumatriptan is a potent vasoconstrictor (hence the often observed rise in BP). Breathing oxygen gets oxygen-rich blood to our head, and since the oxygen supply to the brain is regulated in close tolerances, the vessels are constricted autonomously. And from this follows why oxygen works best if used at the onset of an attack: counteracting the early expansions is best to dampen the positive feedback loop, before things get completely out of whack.
Just my 2 cents, I could be wrong.
Ueli