ENDOTHELIN ETB RECEPTOR-MEDIATED CONSTRICTION IN THE RABBIT BASILAR ARTERY

The present study tests whether endothelin ETB receptor activation can mediate endothelin-1 constriction in the rabbit basilar artery in sit u. Endothelin-1 (30 nM) induced 27% constriction of vessels pretreated with 1 mu M BQ610 (homopiperidenyl-CO-Leu-D-Trp (CHO)-D-Trp-OH), an e ndothelin ETA receptor antagonist, and the resulting constriction was completely relaxed by BQ788(N-cis-2,6-dimethylpiperidinocarbonyl L-gam ma-MeLeu-D-Trp (COOCH3)-Nle), an endothelin ETB receptor antagonist. S imilarly, 30 nM endothelin-1 induced 30% constriction of vessels pretr eated with 1 mu M BQ788, and the resulting constriction was completely relaxed by BQ610. In contrast, sarafotoxin S6c, an endothelin ETB rec eptor agonist, did not induce constriction. This study suggests that i n the basilar artery (1) endothelin ETB receptor activation can result in constriction and (2) the ability to elicit constriction is in some way dependent upon the agonist that activates the endothelin ETB rece ptor. (C) 1998 Elsevier Science B.V. All rights reserved.