title: Properties of aconitine-modified sodium channels in single cells of mouse ventricular myocardium.
abstract: Effects of the plant alkaloid Aconitine on the kinetics of sodium channels were studied in enzymatically isolated single cells of the mouse ventricular myocardium. Aconitine (1 mumol/l) induced a prolongation of the 90% repolarization of action potentials from 52.4 +/- 3.7 ms to 217.0 +/- 12.5 ms. Delayed terminal repolarization and oscillatory afterpotentials preceded spontaneous activity with high frequencies. Peak sodium currents were diminished from 28.0 +/- 9.0 to 14.0 +/- 6.0 nA. The reversal potential of the sodium current was shifted from 16.0 +/- 11.0 to -8.0 +/- 6.0 mV (52.5 mmol/l extracellular sodium concentration) suggesting a decreased selectivity of the Aconitine-modified Na channels. The m-affinity-curves were shifted 31 mV towards more negative potentials at a constant slope. The h affinity-curves were shifted in the same direction by 13 mV. The slope parameter of the h affinity-voltage relationship was enlarged from 9.1 +/- 2.2 mV to 15.6 +/- 4.4 mV. Shifts in m affinity and h affinity resulted in an increased "window". The alkaloid modified channels inactivated extremely slowly at potentials negative to -40 mV, but showed a fast and complete inactivation at potentials positive to -40 mV.
mesh_terms: D000157:Aconitine / Q000494:pharmacology*; D031841:Aconitum / Q000031:analogs & derivatives*; D000818:Animals; D004558:Electric Stimulation; D005260:Female; D006352:Heart Ventricles / Q000187:drug effects*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D009206:Myocardium / Q000166:cytology*
chemical_list: D007473:Ion Channels; D000157:Aconitine