title: An altered beta-adrenoreceptor-mediated modulation of noradrenaline-induced vasoconstriction in spontaneously hypertensive rat mesenteric arteries.
abstract: Pressor responses to bolus injections of noradrenaline (NA) were analysed, in the isolated perfused spontaneously hypertensive (SHR) rat mesenteric arterial bed, in an attempt to investigate the beta-adrenoreceptor-mediated modulation of catecholamine-induced vasoconstriction. NA-induced responses were potentiated in the presence of timolol (10(-7) M) and suppressed by (-)isoprenaline (10(-4) M), indicating the presence of a vasodilator beta-adrenoreceptor population. The suppressant effect of (-)isoprenaline (10(-4) M) was antagonised by timolol (10(-7) M). Lower doses of (-)isoprenaline (10(-7) M - 10(-5) M) potentiated the NA-induced pressor responses, while (+)isoprenaline (10(-5) M - 10(-4) M) suppressed the NA-induced responses. It is concluded that although a vasodilator beta-adrenoreceptor population exists in the SHR mesenteric vasculature, its vasodilator function is compromised when compared to that found in normotensive rats.
mesh_terms: D000818:Animals; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013237:Stereoisomerism; D013999:Timolol / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011943:Receptors, Adrenergic, beta; D015016:Yohimbine; D013999:Timolol; D007545:Isoproterenol; D009638:Norepinephrine