title: Interaction between neuronal amine uptake and prejunctional alpha-adrenergic receptor activation in smooth muscle from canine blood vessels and spleen.
abstract: Experiments were performed to determine the conditions in which norepinephrine release from adrenergic nerve terminals in smooth muscle from canine blood vessels and spleen might be inhibited by prejunctional alpha-adrenergic receptor activation. Strips of aorta, mesenteric and splenic arteries, splenic capsule and portal and saphenous veins were labeled with 7-3H-norepinephrine and mounted for superfusion. In the portal vein, an inhibitory effect of prejunctional receptor activation with exogenous norepinephrine (1.2 X 10(-6) M) on transmitter efflux could be demonstrated during electrical stimulation (9 V, 2 Hz) of the nerve terminals. By contrast, in the other tissues, inhibition of transmitter release during electrical stimulation or depolarization of the nerve terminals with K+ (40 mEq/l) could only be demonstrated aftet blockade of the neuronal uptake mechanism. That activation of prejunctional alpha-adrenergic receptors in blood vessels inhibits the exocytotic process is suggested by the failure of exogenous norepinephrine to affect either the basal efflux of 3-H-norepinephrine or the displacement of 3H-norepinephrine by tyramine.
mesh_terms: D000818:Animals; D001012:Aorta, Abdominal / Q000294:innervation; D001808:Blood Vessels / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D002845:Chromatography; D004285:Dogs; D004558:Electric Stimulation; D008638:Mesenteric Arteries / Q000294:innervation; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism; D009469:Neuromuscular Junction / Q000187:drug effects; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology; D010643:Phenoxybenzamine / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012501:Saphenous Vein / Q000294:innervation; D013157:Splenic Artery / Q000294:innervation; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D010643:Phenoxybenzamine; D009638:Norepinephrine