Effect of isoprenaline on noradrenaline release from sympathetic neurones in rabbit isolated pulmonary artery.
The aim of the present work was to demonstrate the presence of presynaptic beta-adrenoceptors in the rabbit isolated pulmonary artery by investigating the effect of isoprenaline on 3H-noradrenaline (3H-NA) release evoked by electrical field stimulation. (-)-Isoprenaline (10(-7)-10(-6) mol/l) had no effect on the 3H-overflow evoked by stimulation (3 Hz) of the pulmonary artery preloaded with 3H-NA. At 10(-5) mol/l, (-)-isoprenaline reduced the 3H-overflow by maximally 39%. (-)-Isoprenaline (10(-5) mol/l) caused an inhibition that remained almost constant with time. The same results were obtained with (-)-isoprenaline (10(-7)-3 X 10(-5) mol/l) in the presence of cocaine (3 X 10(-5) mol/l), corticosterone (4 X 10(-5) mol/l), and the catechol-O-methyltransferase inhibitor U-0521 (3',4'-dihydroxy-2-methylpropiophenone) (10(-4) mol/l). In the presence of cocaine plus corticosterone, (-)-isoprenaline (3 X 10(-10)-10(-7) mol/l) had no effect on the 3H-overflow evoked by stimulation at 1 Hz. At 10(-6) mol/l, (-)-isoprenaline slightly reduced the 3H-overflow. At 10 Hz, (-)-isoprenaline (10(-6)-3 X 10(-5) mol/l) decreased the 3H-overflow and had no effect at 10(-7) mol/l. In the presence of either rauwolscine (10(-6) mol/l), phentolamine (10(-6) mol/l) or the phosphodiesterase inhibitor ICI 63,197 (3 X 10(-5) mol/l), (-)-isoprenaline (10(-7)-10(-6) mol/l) did not enhance the stimulation-evoked 3H-overflow. (+/-)-Propranolol (10(-7)-10(-5) mol/l) did not alter the stimulation-evoked 3H-overflow.(ABSTRACT TRUNCATED AT 250 WORDS)
Nedergaard
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OA
Department of Pharmacology, School of Medicine, Odense University, Denmark.
D000818:Animals; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D011651:Pulmonary Artery / Q000294:innervation* / Q000378:metabolism; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000378:metabolism / Q000502:physiology*; D014316:Tritium
D011943:Receptors, Adrenergic, beta; D014316:Tritium; D011433:Propranolol; D007545:Isoproterenol; D009638:Norepinephrine