Evidence for the existence of postsynaptic beta-1 and beta-2 adrenoceptors in isolated simian facial veins.

With the use of a steel cannula inserting method, the actions of the beta-adrenoceptor agonists, noradrenaline (NA, a mixed agonist), isoprenaline (a mixed agonist), dobutamine (a selective beta-1 agonist), salbutamol, and procaterol (selective beta-2 agonists), were investigated on isolated and perfused simian facial veins. Each beta-agonist usually induced a vasodilation in a dose-related manner in non-preconstricted vessel preparations. The rank order of potency was isoprenaline much greater than NA greater than dobutamine greater than salbutamol greater than procaterol. NA- and isoprenaline-induced vasodilations were inhibited by either metoprolol (a selective beta-1 adrenoceptor antagonist) or ICI 118,551 (a selective beta-2 antagonist). After beta-1 blockade, NA produced a vasoconstriction which was readily blocked by bunazosin (an alpha-1 antagonist). Dobutamine-induced vasodilations were strongly suppressed by metoprolol and slightly blocked by ICI 118,551. Salbutamol-induced vasodilations were blocked by metoprolol, while ICI 118,551 more markedly inhibited these dilations. From these results, it was concluded that there are abundant beta-adrenoceptors and predominantly beta-1 adrenoceptors in isolated simian facial veins.