Increased noradrenaline release in rat portal vein during sympathetic nerve stimulation due to activation of presynaptic beta-adrenoceptors by noradrenaline and adrenaline. |
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Authors: | Carl Dahlöf Bengt Ljung Bengt Åblad |
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Affiliation: | Department of Pharmacology, AB Hässle, Fack, S-431 20 Mönldal, Sweden |
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Abstract: | With the aim of investigating whether exogenous noradrenaline (NA) and adrenaline (A) can modulate transmitter release via the stimulation of presynaptic beta-adrenoceptors, 3H-release from isolated portal veins was studied after pretreatment with 3H-1-NA, phenoxybenzamine, desipramine and normetanephrine. NA (10 muM) and A (0.05 muM) increased the fractional 3H-release elicited by sympathetic nerve stimulation by 30%. This effect could be blocked by d, 1-propranolol which per se reduced the release by 10%. It is concluded that NA can facilitate its own release via a presynaptic beta-adrenoceptor-mediated positive feed-back mechanism and that adrenaline can stimulate this beta-adrenoceptor-mediated mechanism. |
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Keywords: | Noradrenaline Portal vein Presynaptic β-adrenoceptor Propranolol Transmitter release |
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