title: Effects of 7-O-demethylisothalicberine, a bisbenzylisoquinoline alkaloid of Berberis chilensis, on electrical activity of frog cardiac pacemaker cells.
abstract: 1. In spontaneously beating preparations of sinus venosus of the chilean frog Caudiverbera caudiverbera, the electrophysiological effects of 7-O-demethylisothalicberine (7-O-DI) on transitional pacemaker cells were investigated. 2. 7-O-DI in concentration 1 x 10(-4) M blocked the action potential of transitional cells. This blockade was preceded by subthreshold oscillations and depolarization of membrane potential. 3. Lower concentration of the drug to induce complete blockade (5 x 10(-5) M), allowed to observe a great depression of bioelectric cell characteristics in transitional fibres. 4. 7-O-DI induced blockade of transitional cells action potential was preceded by the appearance of a notch in their upstroke and the persistence of a fast depolarizing activity that remained unblocked. This 7-O-DI resistant fast component of the upstroke was blocked by tetrodotoxin. 5. Transitional cells completely blocked by 7-O-DI were depolarized to about 40 mV. 6. The results indicate a close similarity between 7-O-DI and verapamil effects on action potential configuration.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, University of Chile, Santiago.
authors.forename: M A
authors.initials: MA
authors.lastname: Morales
authors.forename: L R
authors.initials: LR
authors.lastname: Gallardo
authors.forename: J L
authors.initials: JL
authors.lastname: Martínez
authors.forename: R S
authors.initials: RS
authors.lastname: Puebla
authors.forename: D A
authors.initials: DA
authors.lastname: Hernández
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D044182:Benzylisoquinolines; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D007546:Isoquinolines; D009206:Myocardium / Q000166:cytology; D010946:Plants, Medicinal / Q000032:analysis*; D013779:Tetrodotoxin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D044182:Benzylisoquinolines; D007546:Isoquinolines; D013779:Tetrodotoxin; C062425:7-O-demethylisothalicberine; D014700:Verapamil