Stg 1002 stimulator

Electrical activity of the human cardiomyocytes plated on patterned MEAs was recorded following 4–10 days in vitro (DIV) using a Multichannel Systems 60 channel amplifier (MEA 1040, Multichanel Systems). Prior to recording, the cells were allowed to equilibrate for 15 min in the lab atmosphere at 37°C. Temperature was maintained with a TC02 temperature controller (Multichannel Systems). The cells were stimulated using a STG 1002 stimulator (Multichannel Systems) by applying 1 ms wide bipolar square pulses of 500–700 mV amplitude at increasing frequencies ranging from 0.5 Hz to 2.5 Hz in 0.5 Hz increments. The recording medium was the same as the plating medium. For drug experiments, sotalol, (Sigma, cat#S0278), norepinephrine (Sigma, cat#A7257) or verapamil (Sigma, cat#381195) were added to the bathing medium in increasing concentrations of 10, 30, 100 and 300 μM – sotalol, 0.1, 0.3, 1 and 3 μM – norepinephrine, and 0.3, 1, 3 and 10 μM – verapamil. In all drug experiments, for control and each new drug concentration a total of 5 minutes of recordings were performed, the first 150 seconds with no stimulation, followed by 30 seconds of stimulation, and ended with no stimulation. The data was converted to pClamp (Axon Instruments) format using MC-Data Tool (Multichannel Systems) and analyzed with Clampfit (Axon Instruments) software and software written in Matlab.