Monovalent cation conductance of the sustained inward current in rabbit sinoatrial node cells.
Under the whole cell clamp, superfusion of the rabbit sinoatrial node cells with a Na+-free solution suppressed the sustained inward current (Ist), and the L-type Ca2+ current (ICa,L) could be recorded on depolarization less negative than -40 mV from the holding potential of -80 mV. On the other hand, replacement of Ca2+ with Mg2+ in the external solution suppressed inward-going ICa,L and isolated Ist. Under this condition, Ist measured as a nicardipine-sensitive current showed an activation threshold between -60 and -70 mV. The conductance sequence of Ist for monovalent ions was determined as Na+ > Li+ >> K+ approximately = Cs+ by replacing the external Na+ with these alkali metal ions. The contribution of Ist to the diastolic depolarization is discussed.
Guo
J
J
Department of Physiology, Faculty of Medicine Kyoto University, Sakyo-ku, 606-01 Kyoto, Japan.
Ono
K
K
Noma
A
A
D000818:Animals; D002586:Cesium / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D008094:Lithium / Q000502:physiology*; D011188:Potassium / Q000502:physiology*; D011817:Rabbits; D012849:Sinoatrial Node / Q000166:cytology / Q000502:physiology*; D012964:Sodium / Q000502:physiology*
D002586:Cesium; D008094:Lithium; D012964:Sodium; D011188:Potassium