Cellular effects of gastric electrical stimulation on antral smooth muscle cells in rats

The cellular effects of gastric electrical stimulation (GES), which has recently been introduced as a potential therapy for the treatment of gastroparesis and obesity, were investigated in rat antrum smooth muscle cells (SMCs). Effects on cell membrane potentials of single electrical current pulses (pulse width from 0.1 ms to 200 ms) and 2-s pulse train stimuli with different pulse widths (0.1-4 ms), different frequencies (20-200 Hz), and different intensities were studied: 1) the stimulus amplitude had an exponential relationship to the pulse width from 2 ms to 200 ms, along with a rapidly rising strength-duration curve at pulse widths less than 5 ms, and a relatively flat curve at pulse widths greater than 50 ms; 2) when the pulse frequency was at 80 Hz or above, pulse train electrical stimulation, with a pulse width of 2 ms or above but not < or = 1 ms, was able to depolarize cell membrane potentials to above -30 mV and/or generate action potentials. Electrical stimulation with a single long pulse and a width of 50 ms or greater is effective in depolarizing cell membrane potentials of SMCs with low amplitude. Pulse train electrical stimulation with a pulse width of < or = 1 ms fails to generate action potentials in SMCs, whereas pulse train electrical stimulation with a pulse width of 2-4 ms and a sufficiently high pulse frequency is able to generate action potentials. These cellular findings may be useful in optimizing stimulation parameters of GES.