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 mechanisms of membrane electrogenesis through β-adrenergic receptors, the electrophysiological effects 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 importance of this mediator of cellular signaling in modulating the electrical activity of cardiomyocytes in rats of different ages. This study was conducted on the isolated atrial myocardium (with a preserved sinoatrial node and persistent spontaneous activity) of white rats aged 7-, 21- and 100-days using microelectrode techniques. Methoxamine-induced α1-AR stimulation in right atrial cardiomyocytes led to an increase in the frequency of action potential (AP) generation. Methoxamine (10–8 M) increased the AP duration in 7-day-old rats, while decreasing it in 21- and 100-day-old rats. U-73122 completely blocked the effect of methoxamine in all age groups, suggesting an important role of PLC in these processes. The results demonstrate that age exerts influence on the response of cardiomyocytes to α1-AR stimulation, while PLC is a key element in the mechanisms underlying these effects.