title: In vitro effect of 6-hydroxydopamine on isolated rat atria.
abstract: In vitro treatment with 6-hydroxydopamine (6-OHDA), but not with oxidized 6-hydroxydopamine, caused transient, positive inotropic and chronotropic responses in the isolated rat atria. In the presence of rat blood plasma, the excitatory effect of 6-hydroxydopamine persisted unless the drug was washed out by fresh medium. 6-Hydroxydopamine failed to elicit the excitative response in the atria obtained from reserpinized rats or rats treated with 6-hydroxydopamine in vivo. In vitro treatment with 6-hydroxydopamine did not cause the development of supersensitivity to noradrenaline. Cocaine and desipramine, but not bretylium, inhibited the excitative action of 6-hydroxydopamine. No tachyphylaxis developed after repeated exposure to 6-hydroxydopamine in vitro. Propranolol, but not phentolamine, blocked the excitatory effect of 6-hydroxydopamine. It is thus concluded that in vitro treatment with 6-hydroxydopamine may cause atrial stimulation by an indirect action involving the release of catecholamines as a result of its displacement at the nerve ending.
mesh_terms: D000818:Animals; D001949:Bretylium Compounds / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009411:Nerve Endings / Q000378:metabolism; D010627:Phenethylamines / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D013618:Tachyphylaxis
chemical_list: D001949:Bretylium Compounds; D010627:Phenethylamines; D012110:Reserpine; D011433:Propranolol; D003042:Cocaine; D003891:Desipramine; D010646:Phentolamine