β‐ADRENORECEPTOR‐MEDIATED MODULATION OF VASOCONSTRICTION IN RAT ISOLATED PERFUSED MESENTERIC ARTERIES

Publisher Website
Google Scholar
Abstract
Pressor responses to bolus injections of noradrenaline [norepinephrine, NE] were studied in the isolated perfused rat mesenteric arterial bed in the presence of .beta.-adrenoreceptor agonists and antagonists to identify a possible .beta.-adrenoreceptor mediated modulation of catecholamine-induced vasoconstrictor effects. NE-induced responses were potentiated in the presence of timolol and (.sbd.)propranolol and suppressed in the presence of (.sbd.)isoprenaline; (+)isoprenaline was less effective against the NE-induced responses. Timolol attenuated the effects of (.sbd.)isoprenaline on NE-induced responses but not those of the stereoisomer (+)isoprenaline. Apparently, the NE-induced pressor effect in the rat mesenteric vasculature is the net result of vasoconstrictor .alpha.- and vasodilator .beta.-adrenoreceptor activation and that the interaction of the 2 opposing adrenoreceptor-mediated effects represents a physiological antagonism.