title: Anomalous response of rabbit papillary muscles to depolarising current: the possible role of the transient outward current. A pharmacological analysis.
abstract: Rabbit papillary muscles under current depolarization generate an anomalous double action potential (AP) instead of a usual repetitive activity characteristic of myocardial fibres of different mammalian species. The mechanism of the double AP consisting of a spike-like and a delayed slow component was analysed using pharmacological approach. No changes in the anomalous double AP were observed in the presence of Cs ions. This contrasted with the inhibitory action of 4-aminopyridine (4-Apy). High sensitivity of the phenomenon to 4-APy suggests a contribution of the transient outward current, previously postulated for rabbit working myocardial fibres, to account for the double AP.
mesh_terms: D015761:4-Aminopyridine; D000200:Action Potentials; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004594:Electrophysiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D014439:Tyramine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000631:Aminopyridines; D007473:Ion Channels; D015761:4-Aminopyridine; D014700:Verapamil; D011188:Potassium; D002118:Calcium; D014439:Tyramine