Power lab data recording system

The left ventricular papillary muscle was pinned between 2 earth-isolated platinum electrodes in a 1.0 mL experimental chamber filled with Tyrode's physiological salt solution (37°C, aerated with 95%O₂–5%CO₂). The papillary muscle was slowly stretched to a maximum preload (5–10 m⋅N) and was then stimulated using the Grass SD9 stimulator (West Warwick, RI, USA) at a frequency of 1 Hz, pulse width of 0.5 ms, and stimulus strength of 20% above threshold. After a 5 min equilibration period, the papillary muscle was then impaled by glass microelectrodes filled with 3M potassium chloride ((World Precision Instruments; Sarasota, FL, USA) filamented borosilicate glass, outer diameter 1.5 mm, tip resistance of 5–15 mΩ) using a silver/silver chloride reference electrode. The electrical activity (mV) of a cell was recorded with a Cyto 721 electrometer (World Precision Instruments) connected to a PowerLab data recording system (ADInstruments).

According to the method described by Huang et al (10 (link)), arterial rings isolated from rats were placed in a multi-myograph system (Danish Myo Technology A/S), and changes of the tension of the vessel were recorded by Power lab data recording system (AD Instrument). The arterial rings were bathed in PSS solution, which was changed every 20 min, with 95% O₂ plus 5% CO₂ at 37 °C (pH 7.40). The arterial rings were mounted under an optimal resting tension. This optimal resting tension was the minimum level of stretch that gave the largest force after administration of 60 mM KCl. The rings were allowed to stabilize at optimal resting tension for 90 min before the start of the experiments.