FOREARM VASCULAR-RESPONSES TO SEROTONIN ARE NOT MEDIATED BY PRODUCTS OF CYCLOOXYGENASE

The involvement of cyclooxygenase-derived substances in the forearm ar teriolar responses to serotonin was determined in 10 healthy male volu nteers. Serotonin was infused in five incremental doses (0.003-30 mu g min(-1)) for 2 min each into the brachial artery of the non-dominant forearm. Forearm blood flow (FBF) responses to each dose were measured by strain-gauge venous occlusion plethysmography. The cyclooxygenase inhibitor indomethacin (100 mg) was administered orally following the serotonin infusions. After 90 min the serotonin infusions were repeate d and FBF responses measured. Serotonin caused a biphasic response wit h vasodilatation occurring at low doses (0.003-3 mu g min(-1), P<0.01) and vasoconstriction occurring at the highest dose (P<0.01). There wa s no significant difference in vascular response to serotonin followin g cyclooxygenase inhibition. In conclusion, cyclooxygenase products ar e not involved in the forearm vascular responses to serotonin in healt hy human subjects.