We present an analog neuron circuit consisting of a small number of metal-oxide semiconductor (MOS) devices operating in their subthreshold region. The dynamics of the circuit were designed to be equivalent to the well-known Volterra system to facilitate developing the circuit for a particular application. We show that a simple nonlinear transformation of system variables in the Volterra system enables designing a neuron-like oscillator, which can produce sequences in time of identically shaped pulses (spikes) by using current-mode subthreshold MOS circuits. We present experimental results of the fabricated neuron circuits as well as an application in an inhibitory neural network, where the neurons compete with each other in the frequency and time domains.