title: Increased noradrenaline release in rat portal vein during sympathetic nerve stimulation due to activation of presynaptic beta-adrenoceptors by noradrenaline and adrenaline.
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.
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000378:metabolism*; D003891:Desipramine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology*; D009647:Normetanephrine / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011169:Portal Vein / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D013268:Stimulation, Chemical
chemical_list: D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D009647:Normetanephrine; D010643:Phenoxybenzamine; D011433:Propranolol; D003891:Desipramine; D009638:Norepinephrine; D004837:Epinephrine