Rat caval vein myocardium undergoes changes in conduction characteristics during postnatal ontogenesis
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The electrophysiological properties of the superior vena cava (SVC) myocardium, which is considered a minor source of atrial arrhythmias, were studied in this study during postnatal development. Conduction properties were investigated in spontaneously active and electrically paced SVC preparations obtained from 7–60-day-old male Wistar rats using optical mapping and microelectrode techniques. The presence of high-conductance connexin 43 (Cx43) was evaluated in SVC cross-sections using immunofluorescence. It was found that SVC myocardium is excitable, electrically coupled with the atrial tissue, and conducts excitation waves at all stages of postnatal development. However, the conduction velocity (CV) of excitation and action potential (AP) upstroke velocity in SVC were significantly lower in neonatal than in adult animals and increased with postnatal maturation. Connexins Cx43 were identified in both neonatal and adult rat SVC myocardium; however, the abundance of Cx43 was significantly less in neonates. The gap junction uncoupler octanol affected conduction more profound in the neonatal than in adult SVC. We demonstrated for the first time that the conduction characteristics of SVC myocardium change from a slow-conduction (nodal) to a high-conduction (working) phenotype during postnatal ontogenesis. An age-related CV increase may occur due to changes of AP characteristics, electrical coupling, and Cx43 presence in SVC cardiomyocyte membranes. Observed changes may contribute to the low proarrhythmicity of adult caval vein cardiac tissue, while pre- or postnatal developmental abnormalities that delay the establishment of the working conduction phenotype may facilitate SVC proarrhythmia.
KeywordsMyocardial sleeves Caval veins Atrial fibrillation Conduction of excitation Action potential Postnatal development
Maximum upstroke velocity of action potential
Superior vena cava
Resting membrane potential
Alexandra D. Ivanova carried out electrophysiological experiments, data analysis, and drafted the manuscript. Daria V. Samoilova performed the immunohistochemical staining. Artem A. Razumov carried out the analysis of optical mapping data. Vlad S. Kuzmin conceived and designed the study and drafted and revised the manuscript. All the authors read and approved the final manuscript.
The study was supported by the Russian Foundation for Basic Research (RFBR) (grant no. 18-315-00253).
Compliance with ethical standards
All experimental procedures were carried out in accordance with the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978) and approved by the Ethics Committee of the Biological faculty of MSU.
Conflict of interest
The authors declare that they have no conflict of interest.
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