Action of quinidine on ionic currents of molluscan pacemaker neurons
نویسندگان
چکیده
The effects of quinidine on the fast, the delayed, and the Ca2+-activated K+ outward currents, as well as on Na+ and Ca2+ inward currents, were studied at the soma membrane from neurons of the marine mollusk Aplysia californica. External quinidine blocks these current components but to different degrees. Its main effect is on the voltage-dependent, delayed K+ current, and it resembles the block produced by quaternary ammonium ions (Armstrong, C. M., 1975, Membranes, Lipid Bilayers and Biological Membranes: Dynamic Properties, 3:325-358). The apparent dissociation constant is 28 microM at V = +20 mV. The blocking action is voltage and time dependent and increases during maintained depolarization. The data are consistent with the block occurring approximately 70-80% through the membrane electric field. Internal injection of quinidine has an effect similar to that obtained after external application, but its time course of action is faster. External quinidine may therefore have to pass into or through the membrane to reach a blocking site. The Ca2+-activated K+ current is blocked by external quinidine at concentrations 20-50-fold higher compared with the delayed outward K+ current. In addition, it prolongs the time course of decay of the Ca2+-activated K+ current. Na+ and Ca2+ inward currents are also blocked by external quinidine, but again at higher concentrations. The effects of quinidine on membrane currents can be seen from its effect on action potentials and the conversion of repetitive "beating" discharge activity to "bursting" pacemaker activity.
منابع مشابه
Shortening of the Action Potential and Reduction of Pacemaker Activity by Lidocaine, Quinidine, and Procainamide in Sheep Cardiac Purkinje Fibers
The ionic mechanism underlying the shortening of the action potential and the reduction in pacemaker activity by lidocaine, quinidine, and procainamide in sheep cardiac Purkinje fibers was investigated using the two-microelectrode voltage clamp technique. In the presence of lidocaine (1.85 to 3.7 x 10"M), steady state currents were shifted outward over a broad range of potentials. In contrast, ...
متن کاملShortening of the Action Potential and Reduction of Pacemaker Activity by Lidocaine, Quinidine, and Procainamide in Sheep Cardiac Purkinje Fibers
The ionic mechanism underlying the shortening of the action potential and the reduction in pacemaker activity by lidocaine, quinidine, and procainamide in sheep cardiac Purkinje fibers was investigated using the two-microelectrode voltage clamp technique. In the presence of lidocaine (1.85 to 3.7 x 10"M), steady state currents were shifted outward over a broad range of potentials. In contrast, ...
متن کاملتأثیــر نیکــل بر مسدود کردن جریان یونــی گذرای کلسیمــی سلولهای گــره سینوسی ـ دهلیزی دست نخورده و سالم قلب خرگوش
The mammalian sino-atrial node is not a uniform tissue in histological and electrophysiological terms. The differences in ionic currents underlying the regional differences in electrial activity are only just beginning to be understood. One of the ionic currents it is thought to play a role in the center of sino-atrial node for action potential upstroke should be transient Ca+2 current ...
متن کاملتفاوتهای ناحیه ای در نقش جریان یونی if در تولید پتانسیلهای پیس میکری سلولهای گره سینوسی – دهلیزی دست نخورده و سالم قلب خرگوش
Background: The sinoatrial (SA) node is not a uniform tissue in terms of its histology and electrophysiology. The regional differences in action potential configuration are well known, for which the difference on ionic currents underlying the regional differences in electrical activity is the most probable cause. The ionic current "if" is though to play a major role in SA node for pace maker sl...
متن کاملShortening of the action potential and reduction of pacemaker activity by lidocaine, quinidine, and procainamide in sheep cardiac purkinje fibers. An effect on Na or K currents?
The ionic mechanism underlying the shortening of the action potential and the reduction in pacemaker activity by lidocaine, quinidine, and procainamide in sheep cardiac Purkinje fibers was investigated using the two-microelectrode voltage clamp technique. In the presence of lidocaine (1.85 to 3.7 x 10"M), steady state currents were shifted outward over a broad range of potentials. In contrast, ...
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عنوان ژورنال:
- The Journal of General Physiology
دوره 83 شماره
صفحات -
تاریخ انتشار 1984