Figure 2

Electrophysiological characterisation of α-MHC⁺ cells. (a) Characteristic cardiac action potential (APs) of puromycin purified α-myosin heavy chain (MHC)⁺ cells. Most APs had a typical cardiac AP morphology but could not be further specified. Only few APs exhibited typical features of pacemaker-like, atrial-like, or ventricular-like APs. The minimal diastolic potential was -60.2 ± 1.1 mV. The maximal upstroke velocity was 22.9 ± 2.2 V/s. APD₉₀, APD₅₀ and APD₂₀ (AP duration from maximum to 90%, 50% and 20% repolarization) were 96.4 ± 4.2 ms, 71.1 ± 3.9 ms, and 41.3 ± 2.6 ms, respectively. Representative recordings showing the effect of (b) carbachol (1 μmol/l) and (c) isoproterenol (1 μmol/l) on the spontaneous AP frequency. Statistical analysis of the effects of (d) carbachol (1 μmol/l) and (e) isoproterenol (1 μmol/l) on the spontaneous AP frequency. Carbachol caused a decrease whereas isoproterenol increased the spontaneous AP frequency.