Cholinergic modulation of activation sequence in the atrial myocardium of non-mammalian vertebrates.
Cholinergic changes of electric activity were studied in isolated atrium preparations from fishes (cod and carp), amphibians (frog) and reptilians (lizard) using the microelectrode technique and high-resolution optical mapping. Perfusion of isolated atrium with acetylcholine (10(-6)-5.10(-5) M) caused gradual suppression of action potential generation and, eventually, completely blocked the excitation in a part of the preparation. Other regions of atrium, situated close to the sinoatrial and atrioventricular junctions, remained excitable. Such cholinergic suppression of electric activity was observed in the atrial myocardium of frog and in both fish species, but not in reptilians. Ba(2+) (10(-4) M), which blocks the acetylcholine-dependent potassium current (I(KACh)), prevented cholinergic reduction of action potential amplitude. In several preparations of frog atrium, cholinergic suppression of excitation coincided with episodes of atrial fibrillation. We conclude that the phenomenon of cholinergic suppression of electric activity is typical for atria of fishes and amphibians. It is likely to be caused by I(KACh) activation and may be important for initiation of atrial arrhythmias.
Abramochkin
Denis V
DV
Department of Human and Animal Physiology, Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia. abram340@mail.ru
Kuzmin
Vladislav S
VS
Sukhova
Galina S
GS
Rosenshtraukh
Leonid V
LV
D000109:Acetylcholine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002347:Carps; D018678:Cholinergic Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D048388:Gadiformes; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006325:Heart Atria; D066298:In Vitro Techniques; D008116:Lizards; D015221:Potassium Channels / Q000502:physiology; D011898:Ranidae; D013045:Species Specificity; D014714:Vertebrates / Q000502:physiology*
D018678:Cholinergic Agents; D015221:Potassium Channels; D000109:Acetylcholine