Role of Phospholipase C in Age-Related Modulation of Electrical Activity of Atrial Cardiomyocytes upon Stimulation of α1-Adrenergic Receptors in Rats

While current research focuses mainly on the regulatory mechanismsof membrane electrogenesis through β-adrenergic receptors, the electrophysiologicaleffects of α1-adrenergic receptors (α1-ARs) remain poorly understood.The involvement of phospholipase C (PLC) in these effects is unclear,and a study of methoxamine, a nonselective agonist of α1-AR subtypes,in the presence of the PLC inhibitor U-73122 may clarify the importanceof this mediator of cellular signaling in modulating the electrical activityof cardiomyocytes in rats of different ages. This study was conductedon the isolated atrial myocardium (with a preserved sinoatrial nodeand persistent spontaneous activity) of white rats aged 7-, 21-and 100-days using microelectrode techniques. Methoxamine-inducedα1-AR stimulation in right atrial cardiomyocytes led to an increasein the frequency of action potential (AP) generation. Methoxamine(10^–8 M) increased the AP duration in7-day-old rats, while decreasing it in 21- and 100-day-old rats.U-73122 completely blocked the effect of methoxamine in all agegroups, suggesting an important role of PLC in these processes.The results demonstrate that age exerts influence on the responseof cardiomyocytes to α1-AR stimulation, while PLC is a key elementin the mechanisms underlying these effects.