The functional alpha-adrenoceptor in dog caudal vesical arteries is mainly an alpha1A subtype

1 The present study attempted to pharmacologically characterize the subtypes of alpha-adrenoceptors mediating the vasoconstriction in the isolated and perfused canine vesical artery. 2 Noradrenaline (NA) and phenylephrine (PE, an alpha1-adrenoceptor agonist) induced a dose-dependent vasoconstriction, whereas xylazine (an alpha2-agonist) did not induce any clear vascular constrictor response. 3 Prazosin at 0.01 microM and rauwolscine at 0.1 microM failed to affect the NA-induced vasoconstriction. Prazosin at 0.1 microM antagonized the vasoconstrictor responses to NA, with pKB value of 7.8. 4 WB 4101 at 0.01-0.1 microM dose-dependently inhibited the responses to NA, with a pKB value of 8.9. The vasoconstrictor responses to NA were not significantly affected by chloroethylclonidine (10-30 microM) or BMY 7378 (0.1 microM). 5 The present results indicate that the canine vesical arteries dominantly contain alpha1-adrenoceptors but have no alpha2-adrenoceptors, and the functional subtype of alpha1-adrenoceptor is characterized as an alpha1A-adrenoceptor subtype.