Demonstration of alpha 2-adrenoceptor-mediated contraction in the isolated canine saphenous artery treated with Bay K 8644.

Contractions to B-HT 920 in the plantar branch of the canine saphenous artery in vitro occurred consistently only in the presence of the calcium channel agonist, Bay K 8644 (30 nM). These results indicate that prior activation of the calcium channel may be required to elicit a subsequent response to B-HT 920 in this artery. Furthermore, the contractile response was inhibited by rauwolscine (10 nM) and was unaffected by prazosin (10 nM), indicating that the response is mediated by postjunctional alpha 2-adrenoceptors.