Selective antagonism of S2-serotonergic receptors relieves but does not prevent cold induced vasoconstriction in primary Raynaud's phenomenon.

In a double blind placebo crossover study, intravenous ketanserin, an antagonist of S2-serotonergic receptors, did not improve plethysmographically monitored digital blood flow during controlled cold challenge in 4 women with carefully defined primary Raynaud's phenomenon. However, ketanserin, if administered at the time of cold induced vasoconstriction, caused prompt vasodilation. These results suggest that serotonin is a contributory element in the maintenance of cold induced vasospasm but that other factors, presumedly adrenergic, initiate the vasoconstrictive response.