SEROTONIN-INDUCED CONTRACTION IN CANINE CORONARY-ARTERY AND SAPHENOUS-VEIN - ROLE OF A 5-HT1D-LIKE RECEPTOR

The identity of the serotonin (5-HT) receptors(s) that mediate(s) cont raction in canine coronary artery and saphenous vein remains controver sial. Ring segments of endothelium-denuded coronary artery and helical strips of saphenous vein were suspended in organ chambers for measure ment of isometric force. 5-HT, alpha Me-5-HT and sumatriptan contracte d both coronary artery and saphenous vein and the non-selective 5-HT r eceptor antagonist 1-naphthylpiperazine (100nM) blocked 5-HT- and suma triptan-induced contraction in both tissues. The agonist rank order po tency for contraction (5-HT>sumatriptan>alpha Me5-HT>MeOT>5-MeT) was s imilar in both tissues and was consistent with that for a 5-HT1D recep tor. Oligonucleotide primers specific for the 5-HT1D receptor sequence was designed for use in a polymerase chain reaction (PCR). cDNA deriv ed from total RNA or mRNA from canine tissues was used in the PCR. PCR resulted in the amplification of a 632 base pair sequence in both can ine coronary artery and saphenous vein; consistent with that expected for the 5-HT1D receptor. Southern blot analysis, with an oligonucleoti de probe internal to the sequence amplified by the PCR primers, confir med that the sequence amplified by PCR with the 5-HT1D receptor. Thus, the 5-HT1D receptor is expressed in canine coronary artery and saphen ous vein and taken together with the pharmacological data, supports th e possibility that a 5-HT1D-like receptor mediates contraction in thes e two tissues.