(:Unkn) Unknown, University, My, Xiongwen Chen, Steven R. Houser
T-type Ca²+ channels (TTCCs) are expressed in cardiac pacemaker cells and conduction system of mammals. However, the roles of TTCCs in heart rate (HR) generation and regulation, and arrhythmias are not well understood. In the mouse, the major TTCC expressed in the heart is Cav3.1/a1G, and therefore we used Cav3.1/ 1G transgenic (TG) and knockout (KO) mice respectively to define the role of TTCC in the heart rate generation, regulation and arrhythmias. Telemetric (conscious) and surface
more » ... nd surface (anesthetized) electrocardiogram (ECG) were used to determine the baseline HR and the effect of isoproterenol (ISO) on the HR in vivo. To reduce the complication of in vivo HR regulation, Langendorff ECG (a technique to record ECG from the surface of Langendorff-perfused, spontaneously-beating, mouse hearts) was used to measure HR at baseline and after ISO stimulation. The basal firing rates and ISO-induced dose-response on the firing rate of sinoatrial nodal cells (SANCs) were studied. Whole cell voltage clamp was used to study the effects of ISO on ICa-L and ICa-T and the underlying mechanism with ventricular myocytes of 1G DTG (Cav3.1/a1G double transgenic) mice. The ICa-T before and after ISO application on a1G DTG, KO and control SAN cells were also measured. At baseline, telemetric ECG ( a technique to record ECG by a wireless ambulatory central monitoring system from the implanted transmitters) recording showed no significant difference in HR between the Cav3.1/a1G TG mice, Cav3.1/a1G KO mice and control mice. ISO increased the HR in conscious mice to the same extent in both DTG and KO mice. However, when the central nervous system regulation is depressed (anesthetized) or removed (ex-vivo Langendorff perfusion), the percentage of HR increase after ISO application was significantly enhanced in the TG mice but reduced in the KO mice. At the cellular level, both at baseline and under all different ISO concentrations, Cav3.1/a1G KO SANCs had significantly slower firing rates than those of control SANCs. ISO induced smaller beat [...]
doi:10.34944/dspace/1715 fatcat:3avyojtnybhufhm5xdsczfsykm