Reciprocal role of the inward currents ib, Na and i(f) in controlling and stabilizing pacemaker frequency of rabbit sino-atrial node cells.
Experiments and computations were done to clarify the role of the various inward currents in generating and modulating pacemaker frequency. Ionic currents in rabbit single isolated sino-atrial (SA) node cells were measured using the nystatin-permeabilized patch-clamp technique. The results were used to refine the Noble-DiFrancesco-Denyer model of spontaneous pacemaker activity of the SA node. This model was then used to show that the pacemaker frequency is relatively insensitive to the magnitude of the sodium-dependent inward background current ib, Na. This is because reducing ib, Na hyperpolarizes the cell and so activates more hyperpolarizing-activated current, i(f), whereas the converse occurs when ib, Na is increased. The result is that i(f) and ib, Na replace one another and so stabilize nodal pacemaker frequency.
Noble
D
D
University Laboratory of Physiology, Oxford, U.K.
Denyer
J C
JC
Brown
H F
HF
DiFrancesco
D
D
D000818:Animals; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology*; D008433:Mathematics; D008564:Membrane Potentials; D008955:Models, Cardiovascular; D011817:Rabbits; D012849:Sinoatrial Node / Q000502:physiology*; D015222:Sodium Channels / Q000502:physiology
D007473:Ion Channels; D015222:Sodium Channels