The role of potassium currents in the formation of action potential morphology of true pacemaker cells in the mouse sinoauricular node (SAN) was studied. Biophysical parameters were recorded in cells using microelectrode. Pharmacological analysis was performed by applying specific potassium channel blockers, as well as a non-selective current channel activated by hyperpolarization HCN. It was found that the true pacemaker cells are located along the SAN artery and differ in the slowest velocity of action potential (AP) upstroke dV/dtmax (≈3 V/s). Ivabradine (3 µmol) decreased the frequency of AP generation by 24% due to an increase in the duration and velocity of the slow diastolic depolarization (SDD) phase. E4031- blocker of fast inward potassium current, I Kr, affected the duration and velocity of the repolarization phase. E4031 (1 µmol) caused an increase in SDD duration and a decreased in the frequency of AP generation. Complete inhibition of I Kr channels can cause depolarization of the sarcolemma and blocks of electrical activity. Chromanol 293B blocked the channels of slow inward potassium current, I Ks. The contribution of IKs to the repolarization phase was 20-30%. The frequency of AP generation slowed down by an average of 7%. The I to current made a significant contribution to the frequency of AP generation in SAN cells of the mouse. 4-AP aminopyridine - blocker of I to channels (0.5 mmol) caused an increase in AP duration by an average of 43%, and in the concentration of 5 mmol - by 80%. At the same time, the frequency of AP generation decreased by 14%. Thus, potassium currents play a key role in the formation of AP in the mouse CA node cells and participate in the modulation of the rhythm of spontaneous contractions.
sinoauricular node, action potential, slow diastolic depolarization, potassium currents, blockers, mouse
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