SUMATRIPTAN RELAXES ISOLATED PORCINE OPHTHALMIC ARTERY, BUT INHIBITS VIP-INDUCED RELAXATION

Sumatriptan, a 5-hydroxytryptamine (5HT)(1)-like receptor agonist, is a new antimigraine drug which is also effective in cluster headache (C H), a disorder with marked ocular circulatory abnormalities. Sumatript an could putatively exert a therapeutic effect in this vascular bed. T he present study is an attempt to assess sumatriptan's vasoactivity in isolated porcine ophthalmic artery (POA) and to verify whether it has similar activity to 5HT, and whether it interferes with the vasodilat ion induced by calcitonin gene-related peptide (CGRP) and vasoactive i ntestinal peptide (VIP). In contrast to 5HT, sumatriptan induced only slight contraction in POA at high concentrations. However, in some art ery segments pre-contracted with PGF(2 alpha), sumatriptan induced a s light and short-lasting but marked relaxation. In addition, relaxation s induced by VIP were inhibited significantly by sumatriptan, whereas CGRP effects were not influenced by the drug. Such reactions suggest t hat sumatriptan's effect in CH is probably unrelated to direct ocular arterial vasoconstriction.