Fig. 1. The negative chronotropy induced by propofol stimulation in cultured rat ventricular myocytes. (  A ) Records of the beating of myocytes obtained with the Fotonic Sensor at each concentration of propofol. (  B ) Beating rates after SFD addition (open squares) and 100 nM (closed triangle), 1 μM (open triangle), 10 μM (closed circle), 50 μM (open circle), and 100 μM (closed squares) propofol stimulation (n = 4–14). (  C ) Dose–response curve of propofol using the data at 5 min after stimulation. The value of IC⁵⁰is 39 ± 16 μM. Data are expressed as the percent of control (before stimulation) and show the mean ± SE. Propofol stimulation decreased the beating rate in a dose-dependent manner. *  P < 0.05  versus vehicle (SFD).