The effects of the specific blockers of the inward Na-current --lidocaine and tetrodotoxin (TTX) were studied with microelectrode technique on the spontaneously beating strips of the mouse sinoauricular (SA) area. Lidocaine (25 microM) and TTX (25 pM) increased the duration of the peak of the action potentials (AP) of true pacemaker cells by extending the plateau phase (phase 2 or APD 20), slowing the dV/dt max from 2.6 +/- 0.8 V/s (n = 25) to 1.4 +/- 0.3 V/s (n = 5, p < 0.05) and reducing the velocity of diastolic depolarization (DD) by 20%. The extend of the dV/dt max value decline depended on the lidocaine concentration. The experimental data fully meted to Hill equation. The lidocaine threshold concentration was 20 microM. The lidocaine effective concentration which decreased dV/dt max by 50% (EC50) was 35 microM. The TTX (25 microM) exposure decreased the dV/dt max from 1.6 V/s to 0.8 V/s and DD velocity slowed by 49%. It should be noted that TTX also increased the duration of APD20. Our data show that dV/ dt max of the true pacemaker cells was reduced by 35-45% after exposure to TTX and lidocaine. This fact confirms the involvement of Na-current in the generation of the upstroke true pacemaker cells AP.
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Dev Dyn
October 2024
Department of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch of the Russian Academy of Sciences, Syktyvkar, Russia.
Background: Maturation of the mouse is accompanied by the increase in heart rate. However, the mechanisms underlying this process remain unclear. We performed an action potentials (APs) recordings in mouse sinoatrial node (SAN) true pacemaker cells and in silico analysis to clarify the mechanisms underlying pre-postnatal period heart rate changes.
View Article and Find Full Text PDFFront Pharmacol
January 2024
Department of Chemistry, The University of Jordan, Amman, Jordan.
Cardiovascular diseases (CVD) continue to threaten health worldwide, and account for a significant portion of deaths and illnesses. In both developing and industrialized nations, they challenge their health systems. There are several traditional uses of seeds in Pakistan, India, Iran, and China, including treating cardiovascular, neurological, and urogenital diseases.
View Article and Find Full Text PDFCirc Arrhythm Electrophysiol
September 2023
Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain (A.I., T.G.-S.).
Background: Pulsed field ablation (PFA) is a novel nonthermal cardiac ablation technology based on irreversible electroporation (IRE). While areas of IRE lead to durable lesions, the surrounding regions, where reversible electroporation occurs, recover. The behavior of local electrograms in areas of different electroporation levels remains unknown.
View Article and Find Full Text PDFBull Exp Biol Med
December 2022
Department of Cardiology, Renmin Hospital of Wuhan University & Cardiovascular Research Institute of Wuhan University, Wuhan, China.
To investigate the consequences and mechanisms of myocardium remodeling of aging left atrium, we analyzed the main cardiac electrophysiological parameters such as rest membrane potential, action potential amplitude, maximum rate of action potential increase (max dV/dt), action potential plateau, and 30, 50, and 90% action potential duration (APD, APD, and APD, respectively), as well as the inducibility and duration of atrial arrhythmias in adult and aging rabbits. L-type calcium current was also recorded. The collagen content in the myocardium and ultrastructure of left atrial cells were also studied.
View Article and Find Full Text PDFJ Interv Card Electrophysiol
April 2023
Department of Cardiology, Hubei Provincial Hospital of Traditional Chinese Medicine, Wuhan, 430061, Hubei, China.
Background: Zhigancao decoction (ZD) has a long history in China as a traditional Chinese medicine compound for the treatment of tachyarrhythmias. This study mainly explored the pharmacological mechanism of Zhigancao Decoction in preventing atrial fibrillation by altering the electrical and structural remodeling of the atrial in rabbits.
Methods: In total, 30 male New Zealand white rabbits were randomly divided into 3 groups (ten rabbits for each).
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