Microhollow cathode discharge (MHCD) devices generate microplasmas with high electron densities and reactive species, making them a prospective hydrocarbon reforming technology. Here we report on the electrical phenomena resulting from MHCD devices with elongated trenches using argon at atmospheric pressure and room temperature. Devices that were 100 mu m wide, 100 mm deep, and 1 cm long exhibited self-pulsing current during constant voltage DC power application ranging from 0 mA to 32 mA. The capacitances for MHCDs with trenches 25, 100, and 250 mu m wide were estimated to be 68, 70, and 33 mu F respectively. A current-limited DC supply prevented self-pulsing, and resulted in abnormal, normal, or negative differential resistance (NDR), i.e. hollow cathode, operating modes. The NDR state manifested at lower current limits and occurred when the microplasma in the trench was discontinuous. Simulations from a corresponding, empirically determined circuit model showed larger total average power consumption (including the ballast resistance) during pulsed inputs (5.61-31.08 W) in comparison to constant voltage inputs (<1 W). These findings advance the development of these MHCDs for microplasma reforming applications, providing insights into operational modes and power consumption estimates critical to understanding the overall efficiency in the context of a future microplasma reforming system. (C) 2012 Elsevier B. V. All rights reserved.