Effects of beta-adrenoreceptor blocking drugs on adrenergic transmission.
The peripheral actions of beta-adrenoreceptor antagonists on adrenergic transmitter mechanisms have been reviewed. In addition to receptor blockade, beta-adrenoreceptor antagonists may in high concentrations inhibit neuronal uptake of noradrenaline; inhibit monoamine oxidase; inhibit the uptake of noradrenaline into transmitter storage vesicles and inhibit the extraneuronal uptake of noradrenaline. High concentrations of beta-adrenoreceptor antagonists (threshold about 30 muM) also release noradrenaline from intraneuronal stores; however, their intrinsic sympathomimetic activity is generally attributed to their partial agonist property. Beta-adrenoreceptor antagonists possess adrenergic neurone blocking activity and quinidine-like or local anaesthetic activity. The existance of a positive feedback mechanism involving prejunctional beta-adrenoreceptors is discussed. It is suggested that bradycardia produced by beta-adrenoreceptor antagonists is due to blockade of the action of circulating catecholamines or of transmitter noradrenaline at cardiac extrajunctional beta-adrenoreceptor sites.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D003864:Depression, Chemical; D004558:Electric Stimulation; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011941:Receptors, Adrenergic / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000502:physiology*; D013566:Sympathomimetics / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects*
D000319:Adrenergic beta-Antagonists; D008996:Monoamine Oxidase Inhibitors; D018377:Neurotransmitter Agents; D011941:Receptors, Adrenergic; D013566:Sympathomimetics; D009638:Norepinephrine