Mechanisms of noradrenaline-induced vasorelaxation in isolated femoral arteries of the neonatal rat.
Isolated arteries from the femoral circulation of Wistar rats mounted on a small vessel myograph demonstrated age related tension development to noradrenaline (NA, 1 x 10(-8) - 5 x 10(-5) M) day 20 greater than day 10 (P<0.005); day 100 greater than day 20 (P<0.001) and depolarizing potassium (125 mM) buffer day 20 greater than day 10 (P<0.001). NA evoked dilatation in femoral arteries from neonatal rats (10 days) when added to unstimulated vessels or to those preconstricted with the thromboxane mimetic, U46619. Relaxation to NA was inhibited by L-NAME (0.1 mM) (P<0.001), endothelial removal (P<0.001) and the alpha2-adrenoceptor antagonist, yohimbine (0.1 microM) (P<0.001). Alpha1- or beta-adrenoceptor antagonism was without effect. Relaxation was evoked in femoral arteries of the 10-day-old rats by the alpha2-adrenoceptor agonist UK14304 (1 x 10(-8) - 5 x 10(-5) M). This relaxation was also abolished by L-NAME (0.1 mM) (P<0.001) or endothelial removal (P<0.001). Alpha2-adrenoceptor-mediated vasorelaxation was the predominant response to NA stimulation in femoral arteries of the neonatal rat. These responses were endothelium-dependent and were NO-mediated.
Nishina
H
H
Department of Obstetrics and Gynaecology, University College London.
Ozaki
T
T
Hanson
M A
MA
Poston
L
L
D000818:Animals; D000831:Animals, Newborn; D000068438:Brimonidine Tartrate; D005263:Femoral Artery / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009569:Nitric Oxide / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects*
D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D009569:Nitric Oxide; D000068438:Brimonidine Tartrate; D009638:Norepinephrine