Presynaptic action of adrenaline on adrenoceptors modulating stimulation-evoked 3H-noradrenaline release from rabbit isolated aorta |
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Authors: | Jan Abrahamsen Ove A. Nedergaard |
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Affiliation: | (1) Department of Pharmacology, School of Medicine, Odense University, J. B. Winslows Vej 19, DK-5000 Odense C, Denmark |
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Abstract: | Summary The purpose of this investigation was to study the effect of adrenaline on presynaptic adrenoceptors by recording the release of 3H-noradrenaline evoked by electrical-field stimulation. Adrenaline (10–10–3 × 10–9 mol/l) had no effect on the 3H-overflow evoked by stimulation of aorta preloaded with 3H-noradrenaline. At 10–8 and 3 × 10–8 mol/l, the 3H-overflow was decreased by up to 47%. The maximum decrease was more marked in the presence of either cocaine (3 × 10–5 mol/l) plus corticosterone (4 × 10–5 mol/l), cocaine (3.3 × 10–6 mol/l) plus normetanephrine (4 × 10–5 mol/l), or desipramine (10–6 mol/l) plus normetanephrine (10–5 mol/l). The relationship between adrenaline-induced decrease and stimulation-frequency was dependent on the experimental design: either the decrease was the same at all frequencies (1–16 Hz) or it was more marked, the lower the frequency (1 > 3 > 8 Hz). Phentolamine and rauwolscine (both 10–6 mol/l) antagonized the inhibitory effect of adrenaline (10 – 8–10–6 mol/l). Phenoxybenzamine (10–6 mol/l), prevented the inhibitory effect. No enhancing effect of adrenaline (10–9–10–6 mol/l) was observed in the presence of these three -adrenoceptor antagonists. Our results suggest that adrenaline activates inhibitory 2-adrenoceptors, but not facilitatory -adrenoceptors on postganglionic sympathetic nerve terminals in rabbit aorta.Send offprint requests to J. Abrahamsen at the above address |
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Keywords: | Adrenaline Presynaptic adrenoceptors 3H-Noradrenaline release Rabbit aorta |
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