That's what we used to think. The following is a cut and paste from one of the more learned board members, Bob Johnson, who devotes untold hours to reearching what the medical comunity is doing about CH:

For the 42nd time: the world is not flat!
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Interesting to note that he is saying that the primary mode of action is NOT as a vasoconstrictor but on its effect on the central nervous system. Doesn't change our appreciation of this class of meds but suggests we need to change how we think about the nature of CH.
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Handb Exp Pharmacol. 2007;(177):129-43.   


Serotonin receptor ligands: treatments of acute migraine and cluster headache.

Goadsby PJ.

Institute of Neurology, Queen Square, London WC1N 3BG, UK. peterg@ion.ucl.ac.uk

Fuelled by the development of the serotonin 5-HT(1B/1D) receptor agonists, the triptans, the last 15 years has seen an explosion of interest in the treatment of acute migraine and cluster headache. Sumatriptan was the first of these agonists, and it launched a wave of therapeutic advances. These medicines are effective and safe. Triptans were developed as cranial vasoconstrictors to mimic the desirable effects of serotonin, while avoiding its side-effects. IT HAS SUBSEQUENTLY BEEN SHOWN THAT THE TRIPTANS' MAJOR ACTION IS NEURONAL, WITH BOTH PERIPHERAL AND CENTRAL TRIGEMINAL INHIBITORY EFFECTS, AS WELL AS ACTIONS IN THE THALAMUS AND AT CENTRAL MODULATORY SITES, SUCH AS THE PERIAQUEDUCTAL GREY MATTER. Further refinements may be possible as the 5-HT(1D) and 5-HT(1F) receptor agonists are explored. Serotonin receptor pharmacology has contributed much to the better management of patients with primary headache disorders.

PMID: 17087122 [PubMed]
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J Clin Neurosci. 2010 Mar 11.

What has functional neuroimaging done for primary headache ... and for the clinical neurologist?
Sprenger T, Goadsby PJ.

UCSF Headache Centre, Department of Neurology, University of California, 1701 Divisadero St, Suite 480, San Francisco, CA 94115, USA.

Our understanding of mechanisms involved in primary headache syndromes has been substantially advanced using functional neuroimaging.

THE DATA HAVE HELPED ESTABLISH THE NOW-PREVAILING VIEW OF PRIMARY HEADACHE SYNDROMES, SUCH AS MIGRAINE AND CLUSTER HEADACHE, AS BRAIN DISORDERS WITH NEUROVASCULAR MANIFESTATIONS, NOT AS DISORDERS OF BLOOD VESSELS.

PMID: 20227279 [PubMed]


What I learned from this post is the more we learn, the more we learn we know very little about CH.

Joe