title: Beta-adrenoreceptor-mediated modulation of vasoconstriction in rat isolated perfused mesenteric arteries.
abstract: Pressor responses to bolus injections of noradrenaline (NA) were studied, in the isolated perfused rat mesenteric arterial bed, in the presence of beta-adrenoreceptor agonists and antagonists, in an attempt to identify a possible beta-adrenoreceptor mediated modulation of catecholamine-induced vasoconstrictor effects. NA-induced responses were potentiated in the presence of timolol and (-)propranolol and suppressed in the presence of (-)isoprenaline; (+)isoprenaline was less effective against the NA-induced responses. Timolol attenuated the effects of (-)isoprenaline on NA-induced responses but not those of the stereoisomer (+)isoprenaline. It is concluded that the NA-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 two opposing adrenoreceptor-mediated effects represents a 'physiological antagonism'.
mesh_terms: D000818:Animals; D002395:Catecholamines / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000294:innervation; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects
chemical_list: D002395:Catecholamines; D011941:Receptors, Adrenergic; D008729:Methoxamine; D007545:Isoproterenol; D009638:Norepinephrine; D011224:Prazosin