Reciprocal role of the inward currents ib, Na and i(f) in controlling and stabilizing pacemaker frequency of rabbit sino-atrial node cells. |
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Authors: | D Noble J C Denyer H F Brown D DiFrancesco |
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Affiliation: | University Laboratory of Physiology, Oxford, U.K. |
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Abstract: | 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. |
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