Properties of the hyperpolarization-activated current (I(f)) in isolated mouse sino-atrial cells.
OBJECTIVE
We have investigated the properties of the hyperpolarization-activated (I(f)) current in pacemaker cells from the mouse sino-atrial node (SAN).


METHODS
The I(f) current was studied in cells isolated enzymatically from the SAN region of adult C57BL6/J mice. The whole-cell variation of the patch-clamp technique was employed to investigate the basic properties of I(f).


RESULTS
In mouse SAN cells, the I(f) current density at -120 mV was 18+/-2 pA/pF (n=23). I(f) was not detected in cells showing atrial-like morphology that were also found in SAN preparations (n=7). I(f) was blocked by 5 mM Cs(+), was inhibited by application of 5 microM acetylcholine, and was increased by 10 microM noradrenaline. The I(f) current reversal potential was -31+/-2 mV under physiological concentration of Na(+) and K(+) ions. Lowering the extracellular Na(+) concentration reduced I(f) amplitude, while increased when the extracellular K(+) concentration was augmented. I(f) voltage for half activation was -87+/-1 mV (n=6).


CONCLUSIONS
We conclude that the native I(f) current in mouse SAN cells shows functional properties that are similar to I(f) described in rabbit SAN tissue. This study opens the possibility of investigating the involvement of I(f) in the regulation of heart rate in genetically modified mice.
Mangoni
M E
ME
UPR 1142,CNRS, Institut de Génétique Humaine, 141 rue de la Cardonille, 34396 Cedex 5, Montpellier, France. matteo.mangoni@igh.cnrs.fr
Nargeot
J
J
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002586:Cesium / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000494:pharmacology; D012849:Sinoatrial Node / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology
D007473:Ion Channels; D002586:Cesium; D012964:Sodium; D000109:Acetylcholine; D011188:Potassium; D009638:Norepinephrine